Dr. Jeff Masters' WunderBlog

Earl maintaining Category 4 strength; hurricane watches for North Carolina

By: JeffMasters, 9:44 PM GMT on August 31, 2010

Hurricane watches are now posted for coastal North Carolina, as Hurricane Earl continues towards the west-northwest at 13 mph with little change in strength. Currently, the outer reaches of the storm are affecting the Turks and Caicos Islands, and NOAA's Wavewatch III model is predicting 15 - 20 foot waves are affecting these islands. Early this morning, waves at buoy 41043 offshore of Puerto Rico reached 31 feet. Winds at Providenciales in the Turks were only 20 - 25 mph this afternoon, though Cockburn Town and Balfour Town in the extreme eastern Turks may be seeing winds near tropical storm force--40 mph.


Figure 1. Afternoon satellite image of Earl.

Intensity forecast for Earl
Recent visible satellite loops show that the southwest side of Earl is getting eaten into by wind shear and dry air. The storm is no longer as symmetrical as 24 hours ago, and the spiral band on Earl's west side has been destroyed by dry air. Wind shear as diagnosed by the latest SHIPS model forecast shows a moderate 10 - 20 knots of wind shear, due to upper level winds out of the southwest from a trough of low pressure to Earl's west. This moderate shear is predicted to continue through Friday. Water vapor satellite loops show some moderately dry air to Earl's southwest, and very dry air to the northwest. Once Earl works its way farther to the northwest, it is possible that the persistent moderate wind shear will be able to drive this dry air deep enough into Earl's west side to significantly disrupt it. However, none of the models is predicting this, and Earl is probably large and strong enough to fend off this sort of assault. I give a 30% chance that a major dry air intrusion will significantly disrupt Earl between now and Thursday, weakening it to a Category 2 hurricane. Ocean temperatures are a near-record 29.5 - 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content favorable for intensification. Earl is undergoing an eyewall replacement cycle, which may diminish its winds by 10 - 20 mph for a day or so. There is no evidence that Earl has weakened, though, based on the latest pressure of 940 mb from the Hurricane Hunters. It is likely Earl will be a major Category 3 or 4 hurricane at its closest approach to North Carolina Thursday night and Friday morning. By Friday night, when Earl will be making its closest approach to New England, wind shear will rise to a high 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 2 hurricane on Friday night, when it could potentially make landfall in Massachusetts. Earl is more likely to be a Category 1 hurricane on Saturday morning, when it could potentially make landfall in Maine or Nova Scotia, Canada.

Track forecast for Earl
The latest set of computer models runs from 8am EDT (12Z) are pretty unified in taking Earl 100 - 200 miles off the coast of North Carolina, then 150 - 300 miles off the coast of Southeast Massachusetts, then into Nova Scotia. The high degree of model unity gives confidence that this is the correct solution, but it is good to keep in mind that the average error in a 48-hour NHC forecast is about 125 miles. It is likely that Earl will bring a 15-hour period of heavy rain and tropical storm force winds of 39+ mph to North Carolina's Outer Banks, beginning on Thursday evening. NHC is giving Cape Hatteras a 15% chance of receiving hurricane force winds. By Friday evening, Southeast Massachusetts can expect a 6 - 8 hour period of heavy rain and tropical storm force winds of 39+ mph. NHC is giving Nantucket a 13% chance of receiving hurricane force winds. These odds are 5% for Boston, 6% for Providence, 8% for Eastport, Maine, and 14% for Yarmouth, Nova Scotia. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea. Keep in mind that the average error in position for a 3-day NHC forecast is 185 miles.

Regardless of Earl's exact track, the U.S. East Coast can expect a long period of high waves beginning on Thursday. Significant beach erosion and dangerous rip currents will be the rule, due to waves that will reach 10 - 15 feet in offshore waters. Waves from Hurricane Danielle killed two swimmers in the U.S. over the weekend and forced hundreds of water rescues along the U.S. East Coast. Earl's waves will be worse, and will likely cause millions of dollars in beach erosion damage.

Next update
Dr. Rob Carver is planning an update late tonight, and I'll have a full update in the morning.

Jeff Masters

Hurricane

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Category 4 Earl headed for a close brush with North Carolina

By: JeffMasters, 3:16 PM GMT on August 31, 2010

Powerful Category 4 Hurricane Earl is pulling away from Puerto Rico and the northern Lesser Antilles Islands, and is eyeing its next potential landfall--North Carolina's Outer Banks. Earl brought heavy rain and high winds to Puerto Rico and much of the northern Lesser Antilles yesterday, though it appears that the islands were spared major damage. One exception may be Anegada in the British Virgin Islands, population 200. The eye of Earl passed just north of Anegada at noon yesterday, and Earl's south eyewall probably brought sustained winds of 100 mph to the island. Second hardest hit was probably Anguilla. Amateur weather observer Steve Donahue at anguilla-weather.com estimated gusts of 100 mph on Anguilla; his anemometer broke at 88 mph. Winds in St. Thomas in the U.S. Virgin Islands remained above tropical storm force (39 mph) for five hours yesterday afternoon, peaking at 52 mph, gusting to 62 mph, at 4:49 pm. Heavy rains hit Puerto Rico, where radar-estimated rainfall amounts of up to 5 - 7" occurred. Earl brought waves of sixteen feet to San Juan, and waves at buoy 41043 offshore of Puerto Rico reached 31 feet early this morning.


Figure 1. Morning satellite image of Earl, taken at 10:30am EDT 8/31/10. Image credit: NASA/GSFC.


Figure 2. Radar estimated rainfall for Earl from the San Juan, Puerto Rico radar. Isolated regions of 5 - 7 " of rain occurred in three locations on Puerto Rico. The rays fanning out to east from the radar location marked with a "+" are due to mountains blocking the view of the radar.

Intensity forecast for Earl
Wind shear as diagnosed by the latest SHIPS model forecast shows a moderate 10 - 20 knots of wind shear over Earl, due to upper level winds out of the southwest from a trough of low pressure to Earl's west. This moderate shear is predicted to continue through Friday, but should not appreciably affect Earl, since the hurricane is so large and strong. Ocean temperatures are a near-record 29.5 - 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content favorable for intensification. Earl is undergoing an eyewall replacement cycle, which may diminish its winds by 10 -20 mph for a day or so. However, the storm will probably regain strength after completing this cycle, and it is likely Earl will be a major Category 3 or 4 hurricane at its closest approach to North Carolina Thursday night and Friday morning. By Friday night, when Earl will be making its closest approach to New England, wind shear will rise to a high 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 2 hurricane on Friday night, when it could potentially make landfall in Massachusetts. Earl is more likely to be a Category 1 hurricane on Saturday morning, when it could potentially make landfall in Maine or Nova Scotia, Canada.


Figure 3. Swath of surface winds from Earl predicted by the 2am EDT Tuesday, August 31, 2010 runs of NOAA's GFDL model (left) and HWRF model (right). Hurricane force winds (yellow colors, above 64 knots) are predicted to stay off the coast. Tropical storm force winds (light green colors, above 34 knots) are predicted to affect coastal North Carolina, Massachusetts, and Eastern Maine. Winds between 58 mph - 73 mph (dark green colors) are predicted to small portions of the coast. Image credit: Morris Bender, NOAA/GFDL.

Track forecast for Earl
The latest set of computer models runs from 2am EDT (6Z) this morning push Earl's projected track a little closer to the U.S. East Coast, and we now have two of our six reliable models predicting a U.S. landfall. The latest NOGAPS run shows Earl hitting the Outer Banks of North Carolina late Thursday night, then striking Southeast Massachusetts late Friday night, and Eastern Maine on Saturday morning. The HWRF model predicts a strike on Eastern Maine Saturday morning, but keeps Earl offshore from North Carolina and Massachusetts. None of the other computer models show Earl hitting the U.S., but several models bring Earl within 100 - 200 miles of North Carolina's Outer Banks and Southeast Massachusetts. It is likely that Earl will being a 12-hour period of heavy rain and tropical storm force winds of 39+ mph to North Carolina's Outer Banks, beginning on Thursday evening. NHC is giving Cape Hatteras a 12% chance of receiving hurricane force winds. By Friday evening, western Long Island, Rhode Island, and Southeast Massachusetts can expect a 6 - 8 hour period of heavy rain and tropical storm force winds of 39+ mph. NHC is giving Nantucket a 11% chance of receiving hurricane force winds. These odds are 4% for Boston, 6% for Providence, 5% for Eastport, Maine, and 11% for Yarmouth, Nova Scotia. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea. Keep in mind that the average error in position for a 3-day NHC forecast is 185 miles, which is about how far offshore Earl is predicted to be from Cape Hatteras three days from now. The average error in a 4-day forecast is 255 miles, which is about the distance Earl is expected to be from the coast of New England four days from now.

Regardless of Earl's exact track, the U.S. East Coast can expect a long period of high waves beginning on Thursday. Significant beach erosion and dangerous rip currents will be the rule, due to waves that will reach 10 - 15 feet in offshore waters. Waves from Hurricane Danielle killed two swimmers in the U.S. over the weekend and forced hundreds of water rescues along the U.S. East Coast. Earl's waves will be worse, and will likely cause millions of dollars in beach erosion damage.

Fiona
Tropical Storm Fiona is speeding west-northwest towards Hurricane Earl, but is unlikely to bring tropical storm force winds to the Lesser Antilles. Satellite loops show that heavy thunderstorm activity has increased in some of the outer bands this morning, but remains limited near the center. Wind shear is currently moderate, 10 - 15 knots, and the main impediment to development continues to be dry air associated with the Saharan Air Layer (SAL) surrounding the storm.

Forecast for Fiona
Fiona is moving quickly to the west-northwest, at about 24 mph. This means it is catching up to Earl, which is moving at 15 mph. By tonight, Fiona will be beneath Earl's upper-level outflow channel. Strong upper-level winds from Earl's upper-level outflow and a ridge of high pressure to the northwest of Fiona will bring high levels of wind shear, 20 - 30 knots, to Fiona tonight through Friday, and probably arrest the storm's development. The scenario now called for by all the models is for Fiona to be drawn into the low pressure wake of Earl and turn to the northwest. Fiona will pass to the northeast of the Lesser Antilles, and will probably not bring tropical storm force winds to the islands. Fiona should then continue to the northwest and then turn north, passing very close to Bermuda on Saturday morning. It is possible Earl could destroy Fiona through high wind shear before Saturday.


Figure 4. Morning satellite image of Fiona. High level cirrus clouds flowing out from the center of Earl as part of its upper level outflow can be seen starting to impinge upon the western side of Fiona's circulation.

Danielle is dead
Tropical Storm Danielle has succumbed to the cold North Atlantic waters, and is no longer a tropical storm.

98L
A new tropical wave (Invest 98L) moved off the coast of Africa yesterday, and is centered a few hundred miles south of the Cape Verdes Islands. Strong easterly winds from the African Monsoon are creating a moderate 10 - 20 knots of shear, and the disturbance is currently disorganized. A large area of dry air lies to the north and west of 98L, and this will interfere with development. The latest SHIPS model forecast predicts shear will remain moderate, 10 - 20 knots, for the next five days, and some slow development of 98L is possible as it moves westward at 15 mph. NHC is giving a 10% chance of this system developing into a tropical depression by Thursday, and none of the computer models develop it.


Figure 5. Morning satellite image of 98L.

A rare triple threat in the Western Pacific
Over in the Western Pacific, we have an unusual triple feature--three named storms all within 700 miles of each other. A 3-way interaction between these storms is occurring, making for a very tough forecast situation. The storm of most concern is Typhoon Kompasu, which hit Okinawa today as a Category 2 typhoon. Kompasu is expected to recurve northeastward and hit North Korea on Thursday as a Category 2 typhoon. It is unusual for a powerful typhoon to thread the tight Yellow Sea and hit North Korea, and I don't know how prepared they are for strong typhoons. Kompasu is expected to hit the most populous region of North Korea, but the country is pretty mountainous, and a significant storm surge disaster is probably unlikely. In the South China Sea, Tropical Storm Lionrock and Tropical Storm Namtheun are moving through the straights between Taiwan and China towards each other. Neither are predicted to develop into typhoons, but heavy rains are occurring in Guangdong and Fujian Provinces, further exacerbating the flood conditions China has suffered this summer.


Figure 6. An unusual triple feature over the Western Pacific--three simultaneous named storms all within 700 miles of each other. Image credit: NOAA/SSD.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question to broadcast@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line.

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

I may have a short update this afternoon, once the latest models runs are available.
Jeff Masters

Hurricane

Updated: 7:30 PM GMT on January 03, 2012

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Earl hits Category 4; Fiona forms

By: JeffMasters, 9:01 PM GMT on August 30, 2010

Powerful Hurricane Earl, now a Category 4 storm with 135 mph winds, continues to lash Puerto Rico and the northern Lesser Antilles Islands with heavy rain and high winds this afternoon. Hardest hit was Anegada in the British Virgin Islands, population of 200. The eye of Earl passed just north of Anegada at noon EDT, and the island probably saw sustained winds of 100 mph in the south eyewall of Earl. Second hardest hit was probably the island of Anguilla. Amateur weather observer Steve Donahue at anguilla-weather.com estimated gusts of 100 mph on Anguilla this morning; his anemometer broke at 88 mph. Juliana airport on neighboring St. Martin Island recorded sustained winds of 47 mph, gusting to 68 mph at 8am EDT. Winds were below tropical storm force on Antigua, but heavy rains of 5.71" have deluged the island. Heavy rains have hit Puerto Rico, where radar-estimated rainfall amounts of up to 5" have occurred southwest of San Juan. A heavy rain band moved across the island late this morning, with a tornadic thunderstorm that prompted issuance of a tornado warning.


Figure 1. Afternoon satellite image of Earl.


Figure 2. Radar image of Earl taken this afternoon from the San Juan, Puerto Rico radar.

Outlook for the Caribbean islands today
Latest radar animations out of Puerto Rico show that the eye of Earl has now moved past the Virgin Islands, and winds will begin to subside on most of the islands this evening. Heavy rains will continue through Tuesday, however, bringing the risk of flash flooding and mudslides.

Intensity forecast for Earl
Wind shear as diagnosed by the latest SHIPS model forecast is nearly non-existent over Earl--just 4 knots--but is expected to increase to the moderate range, 10 - 15 knots, tonight through Thursday afternoon, due to upper level winds out of the southwest from a trough of low pressure to Earl's west. This shear should not appreciably affect Earl between now and Thursday, since the hurricane is so large and strong. Ocean temperatures are a near-record 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content highly favorable for continued intensification. Earl should continue to intensify until reaching Category 4 or 5 strength on Tuesday, and will probably maintain major hurricane status through Thursday, when it will make its closest approach to North Carolina. The hurricane will probably undergo at least one eyewall replacement cycle during that period, which will diminish its winds by 20 - 30 mph for a day or so. By Friday, when Earl will be making its closest approach to New England, wind shear will rise to a high 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 2 hurricane on Friday, when it could potentially make landfall in Massachusetts. Earl is more likely to be a Category 1 hurricane on Saturday morning, when it could potentially make landfall in Maine or Nova Scotia, Canada.


Figure 3. Swath of surface winds from Earl predicted by the 8am EDT Monday August 30, 2010 run of NOAA's HWRF model. Hurricane force winds (yellow colors, above 64 kt) are predicted to stay off the coast, except over Nova Scotia. Tropical storm force winds (light green colors, above 34 knots) are predicted to affect virtually the entire U.S. coast from North Carolina to Maine. Winds between 58 mph - 73 mph (dark green colors) are predicted to affect North Carolina's Outer Banks, Southeast Massachusetts, and Eastern Maine. Image credit: Morris Bender, NOAA/GFDL.

Track forecast for Earl
The latest set of computer models runs from 8am EDT (12Z) this morning push Earl's projected track a little closer to the U.S. East Coast, but still keep hurricane force winds offshore. History suggests that a storm in Earl's current location has a 25% chance of making landfall on the U.S. East Coast, and Earl's chances of making a U.S. landfall are probably close to that. We now have one model predicting a U.S. landfall--the latest HWRF model predicts Earl will hit the Maine/Nova Scotia border region on Saturday morning as a Category 1 hurricane. None of the other computer models show Earl hitting the U.S., but the storm will likely come uncomfortably close to North Carolina's Outer Banks and to Massachusetts. Several models now predict Earl will being tropical storm force winds of 39+ mph to North Carolina's Outer Banks, beginning on Thursday evening. The Outer Banks of North Carolina and Cape Cod, Massachusetts are both at the edge of the cone of uncertainty, and could potentially receive a direct hit. NHC is giving Cape Hatteras a 11% chance of receiving hurricane force winds. These odds are 10% for Nantucket, 5% for Boston, and 3% for New York City. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea, but it is not unusual for the models to miss the timing and intensity of these troughs significantly in 4 - 5 day forecasts.

Regardless of Earl's exact track, the U.S. East Coast can expect a long period of high waves beginning on Thursday. Significant beach erosion and dangerous rip current will be the rule, due to waves that will reach 10 - 15 feet in offshore waters.

Hurricane History for the northern Lesser Antilles
The last Cape Verdes-type hurricane to affect the Barbuda and the surrounding northern Lesser Antilles Islands was Hurricane Debby of 2000, which passed over the islands on August 28 as a Category 1 hurricane. Damage was less than $1 million, and no fatalities were reported. The last hurricane of any kind to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar took an unusual track, moving towards the northeast, and the storm's eyewall missed all of the islands. Omar did $80 million in damage to the Caribbean, mainly on the islands of Antigua, Barbuda, Dominica, the SSS Islands (Saba, St. Eustatius, and St. Maarten), and the U.S. Virgin Islands. No direct deaths were attributed to Omar, and the name Omar was not retired from the 6-year rotating list of hurricane names.

Links to track Earl
Long range radar out of San Juan, Puerto Rico
Visible rapid scan satellite loop

Fiona forms
Tropical Storm Fiona finally gained enough heavy thunderstorm activity to be given a name, but continues to struggle with dry air. Satellite loops show that heavy thunderstorm activity comes and goes, and there are not many intense thunderstorms near the storm's center. The storm is experiencing low wind shear of less than 5 knots, and is over warm 29°C waters. The main impediment to development continues to be dry air associated with the Saharan Air Layer (SAL) surrounding the storm. The latest SHIPS model forecast calls for shear to increase to moderate, 10 - 15 knots, by Tuesday. Fiona is moving quickly to the west, at about 24 mph. This means it is catching up to Earl, which is moving at 15 mph. By Tuesday night, Earl is expected to be a large and powerful major hurricane with a well-developed upper-level outflow channel heading clockwise out from Earl's center at high altitudes. These strong upper-level winds will bring high levels of wind shear, 20 - 30 knots, to Fiona, and probably arrest the storm's development. A scenario predicted by the GFS, GFDL, and HWRF models is for Fiona to be drawn into the low pressure wake of Earl and pass to the northeast of the Lesser Antilles. Earl would then eventually destroy Fiona through high wind shear, and by robbing the storm of its moisture. An alternative scenario, championed by the ECMWF and NOGAPS models, is for Fiona to stay far enough away from Earl that it will be able to potentially threaten the Bahamas and U.S. East Coast early next week. At this point, it is difficult to choose between these two scenarios. History suggests that a storm in Fiona's current location has a 25% chance of making landfall on the U.S. East Coast.


Figure 4. Afternoon satellite image of Fiona.

Danielle
Danielle is now a tropical storm, and is on its way to oblivion over the cold North Atlantic waters.

Jeff Masters

Hurricane

Updated: 7:47 PM GMT on January 03, 2012

Permalink

Category 3 Hurricane Earl pounding northern Lesser Antilles and Puerto Rico

By: JeffMasters, 2:40 PM GMT on August 30, 2010

An intensifying Hurricane Earl is pounding Puerto Rico and northern Lesser Antilles Islands with heavy rain and high winds this morning. The eye of Earl passed just north of Anguilla at 9am EDT, and Juliana airport on neighboring St. Martin Island recorded sustained winds of 47 mph, gusting to 68 mph at 8am EDT before going silent. An Air Force Hurricane Hunter aircraft currently in Earl just found a central pressure of 960 mb at 9:42 am EDT. This is a significant drop of 25 mb in 25 hours. Top flight level winds at 10,000 feet seen by the Air Force aircraft were 128 mph. Using the usual rule of thumb that the surface winds are 90% of the 10,000 foot flight level winds gives one surface winds of 115 mph, which is right at the border of Cat 2/ Cat 3 strength. Top winds seen at the surface by the Air Force's SFMR instrument were lower, 104 mph. Recent satellite imagery shows that Earl is not perfectly symmetrical--there is still fewer heavy thunderstorms on the hurricane's north side, suggesting that upper-level northerly winds are bringing 5 - 10 knots of wind shear to the storm.


Figure 1. Radar image of Earl taken at 7am EDT 8/30/10 from the St. Maarten radar. Image credit: Meteorological Service of the Netherlands Antilles and Aruba.

Outlook for the Caribbean islands today
Latest radar animations out of Puerto Rico and St. Marten show that the eye of Earl is on track to pass just to the northeast of the islands of Anguilla, St. Maarten, and The Settlement in the British Virgin Islands today. The periphery of Earl's southern eyewall will probably bring Category 1 hurricane conditions to some of these islands today. NHC is giving its highest odds for hurricane-force winds to Saint Maarten--a 99% chance. These odds are 4% for St. Thomas in the Virgin Islands, and 2% for San Juan, Puerto Rico. The main threat to Puerto Rico will be heavy rains--up to eight inches in isolated areas. Earl's rains, in addition to causing flooding and dangerous landslides, will also help alleviate drought conditions that have affected many of the islands this year.

Intensity forecast for Earl
Wind shear as diagnosed by the latest SHIPS model forecast is nearly non-existent over Earl--just 3 knots--put is probably higher than that, based on the fact that the northern portion of Earl cloud pattern is ragged. Further evidence of this is the fact that Earl's eyewall had a gap in its west side, according to the latest report from the Hurricane Hunters. Ocean temperatures are a near-record 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content highly favorable for rapid intensification. These nearly ideal conditions for intensification should bring Earl to Category 4 strength by Tuesday morning, and Category 5 is not out of the question. Earl should be able to maintain major hurricane status through Thursday, when it will make its closest approach to North Carolina. Sea surface temperatures are very warm, 29°C, along the U.S. East Coast, and wind shear is expected to remain low through Thursday. By Friday, when Earl will be making its closest approach to New England, wind shear will rise to a high 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 2 hurricane on Friday, when it could potentially make landfall in Massachusetts or Nova Scotia, Canada.


Figure 2. Swath of surface winds from Earl predicted by the 2am EDT Monday August 30, 2010 run of NOAA's GFDL model. Hurricane force winds (yellow colors, 64 kt and above) are predicted to stay off the coast and tropical storm force winds (light green colors, 34 knots and above) are predicted to stay off the U.S. coast, but affect the coast of Canada. Image credit: Morris Bender, NOAA/GFDL.

Track forecast for Earl
Once Earl passes the Lesser Antilles, steering currents favor a northwesterly course towards North Carolina. History suggests that a storm in Earl's current location has a 25% chance of making landfall on the U.S. East Coast, and Earl's chances of making a U.S. landfall are probably close to that. None of the computer models show Earl hitting the U.S., but the storm will likely come uncomfortably close to North Carolina's Outer Banks and to Massachusetts. The latest set of model runs (2am EDT, or 6Z) project Earl will miss North Carolina by 200 - 300 miles on Thursday, and Massachusetts by a similar distance on Friday. Keep in mind that the average error in a 4 - 5 day NHC forecast is 200 - 300 miles, so the East Coast cannot breathe easily yet. The Outer Banks of North Carolina and Cape Cod, Massachusetts are both at the edge of the cone of uncertainty. NHC is giving Cape Hatteras a 9% chance of receiving hurricane force winds. These odds are 14% for Nantucket, 4% for Boston, and 2% for New York City. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea late in the week, with the storm just missing landfall in the U.S., but possibly making landfall in Nova Scotia, Canada.

Regardless of Earl's exact track, the U.S. East Coast can expect a long period of high waves beginning on Thursday. Significant beach erosion and dangerous rip current will be the rule, due to waves that will reach 10 - 15 feet in offshore waters (Figure 3.)


Figure 3. Wave forecast for 8am Friday, September 3, 2010, as produced by the 8pm EDT August 29 run of NOAA's Wavewatch III model. The model is predicting waves of 4 - 5 meters (13 - 16 feet) in the offshore waters from North Carolina to New Jersey.

Hurricane History for the northern Lesser Antilles
The last Cape Verdes-type hurricane to affect the Barbuda and the surrounding northern Lesser Antilles Islands was Hurricane Debby of 2000, which passed over the islands on August 28 as a Category 1 hurricane. Damage was less than $1 million, and no fatalities were reported. The last hurricane of any kind to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar took an unusual track, moving towards the northeast, and the storm's eyewall missed all of the islands. Omar did $80 million in damage to the Caribbean, mainly on the islands of Antigua, Barbuda, Dominica, the SSS Islands (Saba, St. Eustatius, and St. Maarten), and the U.S. Virgin Islands. No direct deaths were attributed to Omar, and the name Omar was not retired from the 6-year rotating list of hurricane names.

Links to track Earl
Wundermap of the northern Lesser Antilles Islands
Long range radar out of San Juan, Puerto Rico
Visible rapid scan satellite loop

97L
The tropical wave (Invest 97L) now 1000 miles east of the Lesser Antilles Islands has a well-defined surface circulation and enough heavy thunderstorms to be classified as a tropical depression, if it can maintain that state for another six or so hours. Satellite loops show the surface circulation clearly, but also that heavy thunderstorm activity has been slow to build. The storm is experiencing low wind shear of less than 5 knots, and is over warm 29°C waters. The main impediment to development continues to be dry air associated with the Saharan Air Layer (SAL) surrounding the storm. The latest SHIPS model forecast calls for shear to stay in the low range, 5 - 10 knots, through Tuesday, and this should allow 97L to organize into a tropical depression today or Tuesday. NHC is giving 97L a 90% chance of developing into a tropical depression by Wednesday.

97L is moving quickly to the west, at about 20 mph. This means it is catching up to Earl, which has slowed down to 14 mph. By Tuesday night, Earl is expected to be a large and powerful major hurricane with a well-developed upper-level outflow channel heading clockwise out from Earl's center at high altitudes. These strong upper-level winds will bring high levels of wind shear, 20 - 30 knots, to 97L, and probably arrest the storm's development. The most likely scenario depicted in the computer models is for 97L to be drawn into the low pressure wake of Earl and pass to the northeast of the Lesser Antilles. Earl would then eventually destroy 97L through high wind shear, and by robbing the storm of its moisture. An alternative scenario is that 97L will stay far enough away from Earl that it will be able to pass through the northern Lesser Antilles islands as a tropical storm on Wednesday and Thursday, then bend northwestwards to potentially threaten the Bahamas and U.S. East Coast. There is a very high degree of uncertainty on what may happen to 97L. History suggests that a storm in 97L's current location has a 25% chance of making landfall on the U.S. East Coast.


Figure 4. Morning satellite image of 97L.

Danielle
Hurricane Danielle is on its way to oblivion over the cold North Atlantic waters, and is only of concern to shipping interests.

Elsewhere in the Tropics
Over in the Western Pacific, tropical cyclone activity is ramping up, with two named storms expected to affect land this week. As is typical in a La Niña year, these storms have developed close to mainland Asia, and don't have a lot of time over water to intensify into strong typhoons. The storm of most concern is Typhoon Kompasu, which is expected to hit Okinawa today and recurve northward into Korea on Thursday. It now appears the Kompasu will not have major impacts on China's largest city, Shanghai. In the South China Sea, the fearsome sounding Tropical Storm Lionrock is forecast to hit the Chinese coast near Hong Kong on Tuesday, but is not predicted to develop into a typhoon.

The GFS model is predicting formation of a tropical depression off the coast of Africa about seven days from now.

Jeff Masters

Hurricane

Updated: 7:54 PM GMT on January 03, 2012

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Earl poised to rapidly intensify ; now pounding northern Lesser Antilles

By: JeffMasters, 1:16 AM GMT on August 30, 2010

It's time to make final preparations and get ready to ride out the storm if you live in the northern Lesser Antilles Islands tonight, as Hurricane Earl is on your doorstep. Earl continues to intensify steadily, though not explosively. An Air Force Hurricane Hunter aircraft found a central pressure of 972 mb at 7:38 pm EDT. This is a significant drop of 13 mb in ten hours. As is usually the case, it takes six or so hours for a hurricane's winds to respond to a major pressure change, and Earl's winds are now beginning to ramp up. Top flight level winds at 10,000 feet seen by the Air Force were 106 mph. Using the usual rule of thumb that the surface winds are 90% of the 10,000 foot flight level winds gives one surface winds of 97 mph, which is right at the border of Cat 1/ Cat 2 strength. Top winds seen at the surface by the Air Force's SFMR instrument were lower, 78 mph, but a NOAA research P-3 in the storm recently saw surface winds of 88 mph. I expect that the Air Force will be measuring Cat 2 surface winds before their mission is over tonight. Martinique radar shows that Earl has a large, 35 mile wide eye. Earl initially formed a smaller eye, but this collapsed almost immediately, and the larger diameter eyewall took over--kind of an instant eyewall replacement cycle right as the eye initially formed, something I don't recall ever seeing before. The latest eye report from 7:38 pm EDT showed that the temperature difference from outside the eye to inside the eye had increased from 3°C to 8°C in just 1 1/2 hours. This is a huge spike in temperature, and indicates that Earl may be on the verge of a period of more rapid deepening, which will likely carry it to Category 3 or 4 strength by Monday night. Recent satellite imagery shows the storm is lopsided, with much more intense thunderstorm activity on the southern side. This is due to 10 knots of wind shear from strong northerly upper level winds, courtesy of the outflow from Hurricane Danielle. This shear has steadily decreased today, and will continue to decrease tonight and Monday.


Figure 1. Radar image of Earl taken at 8:45 pm AST. Image credit: Meteo France.

Track forecast for Earl
Latest radar animations out of Martinique and St. Maarten show that the eye of Earl is on track to pass just to the northeast of the islands of Barbuda, St. Barthelemy, Anguilla, and St. Maartin in the northernmost Lesser Antilles Islands tonight and Monday morning. Since the eye is so wide, it appears that portions of the southern eyewall will pass over these islands. The southern eyewall is where the NOAA aircraft just measured 88 mph winds, so Barbuda could well see sustained winds of 90 mph for a period of up to two hours, since the storm is moving near 14 mph and has a 35-mile wide eye. Since Earl will probably start intensifying rapidly in the next few hours, Anguilla, the last island in the path of Earl's southern eyewall, could see sustained winds near 95 - 105 mph between 7am - 9am AST. These are worst-case scenarios, and hopefully Earl's southern eyewall will barely miss these islands, bringing winds just below hurricane force.

The latest set of model runs (18Z, 2pm EDT) show Earl shooting the gap between Bermuda and the U.S. East Coast over the next five days, and none of the models take Earl ashore over the U.S. North Carolina is now outside the cone of uncertainty. Recall that the average error in a 5-day track forecast is about 300 miles, so it is still too early to be confident Earl will miss the U.S. The most likely landfall location, were Earl to hit the U.S., would be Cape Cod, Massachusetts. A more likely landfall location appears to be Nova Scotia or Newfoundland, but it is too early to say which province is most at risk.

Hurricane History for the northern Lesser Antilles
The last hurricane to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar's eyewall missed all of the islands, but the storm did $80 million in damage to the Caribbean, mainly on the islands of Antigua, Barbuda, Dominica, the SSS Islands (Saba, St. Eustatius, and St. Maarten), and the U.S. Virgin Islands. No direct deaths were attributed to Omar, and the name Omar was not retired from the 6-year rotating list of hurricane names.

Links to track Earl
Martinique radar
St. Maarten radar
Wundermap of the northern Lesser Antilles Islands
St. Maarten weather history for August 29
Long range radar out of San Juan, Puerto Rico (now back up!)
Visible rapid scan satellite loop

I'll have a full update in the morning.

Jeff Masters

Hurricane

Updated: 7:54 PM GMT on January 03, 2012

Permalink

Hurricane Earl takes aim at Lesser Antilles; 5-year anniversary of Katrina

By: JeffMasters, 2:35 PM GMT on August 29, 2010

Hurricane warnings are flying for the islands in the northern Lesser Antilles, as they hunker down a prepare for the arrival of the 3rd hurricane of the 2010 Atlantic hurricane season, Hurricane Earl. Earl, a classic Cape Verdes-type Atlantic hurricane, is a potentially dangerous storm for the islands in its path, should its eyewall pass directly overhead. Earl could intensify significantly as it moves through the islands late tonight and on Monday. An Air Force Hurricane Hunter aircraft found a central pressure of 978 mb at 1:21 pm EDT. This is a significant drop of 7 mb in four hours. Top surface winds were 75 mph, and they noted an eyewall open to the northwest. The incomplete eyewall can also be seen on Martinique radar (figure 1.) Recent visible satellite imagery shows the storm has continues to increase in organization this afternoon. The amount and intensity of Earl's heavy thunderstorms is increasing, low-level spiral bands are steadily building, and upper level outflow is becoming more established in all quadrants except the north. This lack of development on Earl's north side is due to strong upper level northerly winds from the outflow of Hurricane Danielle to the north. These winds are creating about 15 knots of wind shear over Earl, according to the wind shear analysis from the University of Wisconsin CIMSS group. Water vapor satellite images show a large region of dry air from the Sahara lies to the northwest of Earl, but Earl is successfully walling off this dry air with a solid circular region of heavy thunderstorms.


Figure 1. Radar image of Earl taken at 3:45 pm EDT. Image credit: Meteo France.

Intensity forecast for Earl
As Hurricane Danielle pulls away from Earl this afternoon and this evening, shear should fall to the low range, 5 - 10 knots, as predicted by the latest SHIPS model forecast. This should allow Earl to build a complete eyewall by tonight. Once a complete eyewall is in place, Earl will likely undergo a bout of rapid intensification, which could bring it to Category 3 or 4 strength by Tuesday morning. The ocean temperatures are at near record warmth, 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content highly favorable for rapid intensification. Earl should be able to maintain major hurricane status through Thursday, when it will make its closest approach to North Carolina. Sea surface temperatures are very warm, 29°C, along the U.S. East Coast, and wind shear is expected to remain low through Thursday.

Track forecast for Earl
Earl is being steered to the west by the same ridge of high pressure that steered Danielle. Earl is now approaching a weakness in the ridge left behind by the passage of Danielle and the trough of low pressure that pulled Danielle to the north. Earl should move more to the west-northwest today, likely bringing the core of the storm over or just to the northeast of the islands of Barbuda, St. Barthelemy, Anguilla, and St. Maartin in the northernmost Lesser Antilles Islands tonight and Monday morning. NHC is giving its highest odds for hurricane-force winds to Barbuda and Saint Maarten--a 44% and 42% chance, respectively. These odds are 11% for St. Thomas in the Virgin Islands, and 4% for Puerto Rico.


Figure 2. Wundermap view of the Lesser Antilles showing the NHC 5am wind radius forecast for Earl. Tropical storm force winds (dark green colors) were predicted to affect much of the northern Lesser Antilles, with hurricane force winds (yellow colors) predicted to pass just to the north of the islands.

Once Earl passes the Lesser Antilles, steering currents favor a northwesterly course towards North Carolina. History suggests that a storm in Earl's current location has a 25% chance of making landfall on the U.S. East Coast, and Earl's chances of making a U.S. landfall are probably close to that. None of the computer models show Earl hitting the U.S., and the 12Z (8 am EDT) set of model runs have mostly pushed the storm farther from the U.S. East Coast. It is not unusual for the models to make substantial shifts in their 5-day forecasts, and it is still possible that Earl could make a direct hit on North Carolina as a major hurricane on Thursday or Friday. One should pay attention of the cone of uncertainty, and the Outer Banks of North Carolina are in the 5-day cone. NHC is giving Cape Hatteras a 6% chance of receiving hurricane force winds. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea late in the week, with the storm just missing landfall in the U.S., but possibly making landfall in Nova Scotia, Canada. However, five day forecasts can be off considerably on the timing and intensity of such features, and it is quite possible that the trough could be delayed or weaker than expected, resulting in Earl's landfall along the U.S. East Coast. The most likely landfall locations would be North Carolina on Thursday or Friday, or Massachusetts on Friday or Saturday. The GFS and ECMWF models predict that Earl will come close enough to North Carolina on Thursday to bring the storm's outer rain bands over the Cape Hatteras region. The other models put Earl farther offshore, but it currently appears that Earl will not pass close enough to Bermuda to bring tropical storm force winds to that island. It is possible that if 97L develops into Hurricane Fiona and moves quickly across the Atlantic, the two storms could interact and rotate counterclockwise around a common center. Predicting these sorts of interactions is difficult, and the long-term track forecast for Earl will be difficult if a storm-storm interaction with Fiona occurs.

In any case, the U.S. East Coast can expect a long period of high waves from Earl beginning on Thursday. Significant beach erosion and dangerous rip current will be the rule, due to very high waves from Earl (Figure 3.)


Figure 3. Wave forecast for 8am Thursday, September 2, 2010, as produced by the 2am EDT August 29 run of NOAA's Wavewatch III model. The model is predicting waves of 4 - 5 meters (13 - 16 feet) in the offshore waters from Central Florida to Virginia.

Hurricane History for the northern Lesser Antilles
The last hurricane to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar's eyewall missed all of the islands, but the storm did $80 million in damage to the Caribbean, mainly on the islands of Antigua, Barbuda, Dominica, the SSS Islands (Saba, St. Eustatius, and St. Maarten), and the U.S. Virgin Islands. No direct deaths were attributed to Omar, and the name Omar was not retired from the 6-year rotating list of hurricane names.

Links to track Earl
Martinique radar
Wundermap of the northern Lesser Antilles Islands
Long range radar out of San Juan, Puerto Rico (current down for repair.)
Visible rapid scan satellite loop

97L
The tropical wave (Invest 97L) now midway between Africa and the Lesser Antilles Islands has developed a well-defined surface circulation, and appears destined to develop into a tropical storm and follow the path of Danielle and Earl. Satellite loops show the surface circulation clearly, but also reveal that there is not enough heavy thunderstorm activity associated with 97L for it to be called a tropical depression. The storm is experiencing low wind shear of 5 - 10 knots, is over warm 28°C waters, and is battling a region of dry air associated with the Saharan Air Layer (SAL) to its northwest. The latest SHIPS model forecast calls for shear to stay in the low range, 5 - 10 knots, through Wednesday, and this should allow 97L to organize into a tropical depression today or Monday. The storm will follow a track very similar to Danielle and Earl westward towards the Lesser Antilles Islands, and the storm should arrive near the northern Lesser Antilles Wednesday or Thursday. A more northwesterly path is likely for 97L as it approaches the Lesser Antilles, as the storm follows a break in the high pressure ridge steering it, created by Danielle and Earl. It currently appears that the Northern Lesser Antilles Islands may be at risk of at close brush or direct hit by 97L. If 97L moves relatively quickly, arriving at the Lesser Antilles on Wednesday, it is likely to be a weaker system, since it will have less time over water, and will be closer to big brother Earl. Earl is likely to be a large and powerful hurricane at that time, and the clockwise upper level outflow from Earl will bring strong upper-level northerly winds to the Lesser Antilles, creating high wind shear for 97L. However, if 97L moves relatively slowly, and arrives in the Lesser Antilles on Thursday, Earl will be farther away, the wind shear will be lessened, and 97L will have had enough time over water to potentially be a hurricane. Depending upon how fast they have 97L moving, the computer models have a wide variety of solutions for 97L, ranging from a making it a Category 1 hurricane five days from now (GFDL model) to a weak tropical storm five days from now (several models.) History suggests that a storm in 97L's current location has a 25% chance of making landfall on the U.S. East Coast. NHC is giving 97L a 80% chance of developing into a tropical depression by Tuesday.


Figure 4. Morning satellite image of 97L.

Danielle
Hurricane Danielle blew past Bermuda late Saturday night, bringing one rain squall to the island that brought top winds of 26 mph, gusting to 39 mph. Danielle is now on its way out to sea, and will not trouble any more land areas. High surf will continue to affect Bermuda and the east coast of the U.S. and Canada's Maritime Provinces today. The latest near shore water forecast for Cape Hatteras calls for 6 - 8 foot waves today. These waves will gradually subside during the week, then ramp up to 6 - 8 feet again on Thursday, as Hurricane Earl's wave field begins to pound the U.S. East Coast.

Elsewhere in the Tropics
Tropical Storm Kompasu is headed for China, and is predicted to intensify into a Category 2 typhoon by Wednesday and potentially threaten China's largest city, Shanghai. Over 16 million people live in the city, many of them in low-lying areas, and the Chinese will need to take this storm very seriously. In the South China Sea, the fearsome sounding Tropical Storm Lionrock is forecast to hit the Chinese coast near Hong Kong on Tuesday, but is not predicted to develop into a typhoon.

Katrina, five years later
It hardly seems possible that five years have elapsed since that cruel day in 2005 when the world changed forever for so many people in Louisiana, Mississippi, and Alabama. Recovery from the great hurricane is nowhere near complete--the destruction wrought by Katrina still scars the land terribly, and the proud people of the Gulf Coast still suffer tremendously in the aftermath of the disaster. The scale and intensity of the destruction the hurricane brought is truly breathtaking, and can best be appreciated by viewing two of the best chronicles of Katrina's record storm surge--Margie Kieper's remarkable city-by-city aerial tour of the destruction, and extreme weather photographer Mike Thiess' 13-minute video of his storm surge experience in Gulfport, Mississippi. Katrina did do some good, though--it taught us that our nation can unite in the face of an overwhelming challenge to help our fellow citizens in need, and taught us not to be complacent about living in the realm where great hurricanes come.


Figure 5. A man wearing a tiny life jacket and clutching a neon green noodle and a pet dog floats on the remains of a house in Waveland, MS, during Hurricane Katrina. The photo was taken from the second floor window of a home, and the water is close to the roof line of the first floor. The home was at an elevation of about 17 feet, and the surge is close to ten feet deep here. There are electric lines running down from a pole to a home from left to right. In the distance on the right is a home with water up to the roof line. The eye is probably overhead, as the water is relatively calm and there appears to be little wind or rain, even though the pine trees are bent from the recent force of the eyewall winds. The photo was taken by Judith Bradford. Her husband, Bill Bradford, swam out and rescued the man and his dog, and two other people who floated by. He reported that the water was nothing like white water, but was a gentle, continuous flow. He was lucky. In the nearby Porteaux Bay area, a woman watched her fiance get pulled from a tree by the force of the current. The man was washed out into the Gulf and drowned. The image above is described in more detail in Part 9 of Margie Kieper's Katrina storm surge web page.

I'll share with you my personal story of blogging about Katrina. I starting writing blogs during the spring of 2005. For the first few months of this effort, it was a slow time for interesting weather events, and I had trouble finding things to write about. I was relieved when June of 2005 brought me two Atlantic tropical storms to discuss. But as July wore on, and the bombardment of the great Hurricane Season of 2005 began--a record five named storms, three hurricanes, and two major hurricanes, Dennis and Emily, both the strongest hurricanes ever recorded so early in the season--I was ready for less to write about! History was in the making, and the peak part of hurricane season was still a month away. I managed to take advantage of a slight break in the action in mid-August to travel for vacation and business, and the day Katrina was named found me in New York City. I was attending meetings with the Associated Press, who had just signed up to use Weather Underground as the weather provider for their 5000 newspapers. I wasn't able to follow the storm very closely that day, due to the all the meetings. Still, I had a very uneasy feeling about this storm. When one of the AP staff members made the remark, "It sure has been a slow summer for news. We need a big story!" I looked at her hard and thought, "Be careful what you wish for--you might get it!"

I flew home that Thursday afternoon, then made the decision Friday to drive up north with my family and spend a 4-day weekend at my father's house. The Hurricane Season of 2005 had kept me so busy that I hadn't made it up north to see him that summer, and this was my last chance. High speed Internet was not available in his small town of Topinabee on beautiful Mullet Lake, so I knew I'd be spending some slow hours blogging on his dial-up connection. Still, I figured Katrina would quickly recurve to the north and hit the Florida Panhandle before it had a chance to become a major hurricane. It wasn't like this storm would be worst disaster in American history or anything! Wrong. I spent virtually the entire weekend holed upstairs in the computer room, writing increasingly worried and strident blogs, exhorting people in New Orleans and Mississippi to evacuate. Every now and then, I'd emerge downstairs and say hi to everyone, then head back up to my cell to watch really slowly loading pages and write new blogs. Finally, I couldn't take it any more, and talked my family into returning home a day early. My wife couldn't fully understand why I was so agitated--wasn't this just another hurricane like Frances, Jeanne, Charlie, Dennis, or Emily? But, she agreed that we'd better go home that Sunday night before Katrina hit, since I was such a basket case. The next day, when Katrina hit and the full magnitude of the greatest disaster in American history unfolded, she understood. Indeed, three weeks later my wife headed down to the Louisiana disaster zone as a Red Cross volunteer, and she REALLY got an appreciation of why I had been so agitated in the days before Katrina hit.

It is difficult for me to read my Katrina blog posts again, as I relive those days and remember the terrible suffering this storm brought to so many. Let us not forget the people affected by Katrina, and the lessons the great storm taught. My thoughts and prayers are with all of Katrina's survivors on this fifth anniversary of the storm.

Next update
I may be able to post a quick update on Earl late this afternoon or early this evening.

Jeff Masters

Hurricane

Updated: 7:54 PM GMT on January 03, 2012

Permalink

Earl a threat to the Lesser Antilles; Danielle misses Bermuda; 97L organizing

By: JeffMasters, 3:40 PM GMT on August 28, 2010

The Atlantic's first major hurricane of 2010, Hurricane Danielle, is undergoing an eyewall replacement cycle, and has weakened to a Category 2 storm. Danielle peaked in intensity yesterday as a low-end Category 4 storm with 135 mph winds. Danielle is expected to pass well east of Bermuda tonight, bringing winds of 25 - 35 mph to the island. So far this morning, winds have remained below 20 mph at the Bermuda airport. Bermuda radar shows the outermost spiral bands of Danielle are beginning to approach the island. Infrared satellite loops show that Danielle's cloud tops have warmed, indicating weakening. This is due to the collapse of the storm's eyewall. A new eyewall will form today, but by the time the new eyewall forms on Sunday morning, wind shear will rise to a high 20 - 40 knots, ending any chance Danielle has of further intensification. Danielle is destined to recurve out to sea without hitting any land areas. The largest impacts Danielle will have are from its waves. The Bermuda Weather Service is predicting 12 - 18 foot waves today for Bermuda's offshore waters, and large waves of 6 - 8 feet will affect much of the U.S. East Coast today through Sunday. The latest near shore water forecast for Cape Hatteras calls for 6 - 8 foot waves this weekend.


Figure 1. True color image of Danielle taken at 10:25am EDT Friday, August 27, 2010, by NASA's Aqua satellite. At the time, Danielle was a Category 4 hurricane with 135 mph winds.

Tropical Storm Earl
The bigger concern in the Atlantic today is Tropical Storm Earl. Earl continues to follow a track very similar to Danielle's, but is now farther south than Danielle was. Recent satellite imagery shows the storm has changed little in organization this morning. Water vapor satellite images show a large region of dry air from the Sahara lies to the northwest of Earl, and this dry air is keeping Earl's heavy thunderstorm activity relatively meager. The wind shear analysis from the University of Wisconsin CIMSS group shows that northerly upper-level winds due to the outflow from Hurricane Danielle are creating a moderate 10 - 15 knots of shear over Earl. This shear is keeping any heavy thunderstorms from developing on the north side of Earl's center of circulation. The center of circulation is now exposed to view, which is always a sign of a tropical storm struggling with high wind shear. The first flight into Earl is scheduled for 4pm EDT this afternoon, and will be a research mission by NOAA's P-3s. The NOAA jet will also fly tonight to sample the large-scale steering currents. The first regular hurricane hunting mission by the Air Force is scheduled for Sunday morning.


Figure 2. Morning satellite image of Earl.

Intensity forecast for Earl
The latest SHIPS model forecast for Earl predicts that wind shear will remain moderate this afternoon, 10 - 15 knots, then fall a bit to the low to moderate range, 5 - 15 knots through Monday, as Danielle pulls away and its upper-level outflow stops bringing northerly wind shear to Earl. This reduction in shear should allow the storm to build heavy thunderstorms around the entire center of circulation on Sunday, and close off Earl's core from the dry air to the northwest. SSTs will warm from 29°C today to nearly 30°C on Sunday. These very high SSTs, combined with the low shear environment expected Sunday and Monday, should allow to Earl to intensify into a hurricane by Monday. Earl will likely be a major hurricane by Tuesday and Wednesday, as it moves northwestward between Bermuda and the U.S. East Coast.

Track forecast for Earl
Earl is being steered to the west by the same ridge of high pressure that steered Danielle. As Earl approaches the Lesser Antilles on Sunday, a weakness in the ridge left behind by the passage of Danielle will allow Earl the opportunity to move more to the west-northwest, likely bringing the core of the storm just to the northeast of the northernmost Lesser Antilles Islands Sunday night and Monday morning. However, it is possible that Earl could move directly over some of these northernmost islands. NHC is giving Saint Maarten in the northern Lesser Antilles a 57% chance of receiving tropical storm force winds from Earl, and an 18% chance of getting hurricane force winds. Heavy rain squalls and tropical storm force winds should begin affecting the islands Saint Maarten, Barbuda, and Antigua late Sunday night. The odds of Earl bringing tropical storm force winds to Puerto Rico are lower--25%, according to NHC.

Once Earl passes the Lesser Antilles, steering currents favor a northwesterly course towards North Carolina. History suggests that a storm in Earl's current location has a 30% chance of making landfall on the U.S. East Coast. Earl's chances of making a U.S. landfall are probably more like 20%, due to the steering influence of a strong trough of low pressure predicted to move off the U.S. East Coast next Friday. This trough, if it develops as predicted by the long-range GFS, NOGAPS, and ECMWF models, should be strong enough to recurve Earl out to sea late in the week, with the storm missing landfall. However, six-day forecasts can be off considerably on the timing and intensity of such features, and it is quite possible that the trough could be delayed or weaker than expected, resulting in Earl's landfall along the U.S. East Coast Thursday or Friday. The most likely landfall locations would be North Carolina on Thursday, or Massachusetts on Friday. The GFS model predicts that Earl will come close enough to North Carolina on Thursday to bring the storm's outer rain bands over the Cape Hatteras region. The other models put Earl farther offshore, and it is possible that Earl could pass close enough to Bermuda to bring tropical storm force winds to that island. It is possible that if 97L develops into Hurricane Fiona and moves quickly across the Atlantic, as predicted by the GFS model, the two storms could interact and rotate counterclockwise around a common center. Predicting these sorts of interactions is difficult, and the long-term track forecast for Earl has higher than usual uncertainty because of the possibility of a storm-storm interaction with Fiona.

Links to track Earl
Martinique radar
Wundermap of the northern Lesser Antilles Islands

97L
The tropical wave (Invest 97L) about 300 miles southwest of the Cape Verdes Islands remains well-organized, and appears destined to develop into a tropical storm and follow the path of Danielle and Earl. 97L already has a broad, elongated surface circulation, as seen on satellite loops, but only limited heavy thunderstorm activity. The storm is experiencing a moderate 10 - 15 knots of winds shear, is over warm 28°C waters, and is battling a region of dry air associated with the Saharan Air Layer (SAL) to its northwest. The latest SHIPS model forecast calls for shear to drop to the low range, 5 - 10 knots, tonight through Monday, and this should allow 97L to organize into a tropical depression. The storm will follow a track very similar to Danielle and Earl westward towards the Lesser Antilles Islands, and the storm should arrive near the northern Lesser Antilles Wednesday or Thursday. A more northwesterly path is likely for 97L as it approaches the Lesser Antilles, as the storm follows a break in the high pressure ridge steering it, created by Danielle and Earl. It currently appears that the Northern Lesser Antilles Islands may be at risk of at close brush or direct hit by 97L. If 97L moves relatively quickly, arriving at the Lesser Antilles on Wednesday, it is likely to be a weaker system, since it will have less time over water, and will be closer to big brother Earl. Earl is likely to be a large and powerful hurricane at that time, and the clockwise upper level outflow from Earl will bring strong upper-level northerly winds to the Lesser Antilles, creating high wind shear for 97L. However, if 97L moves relatively slowly, and arrives in the Lesser Antilles on Thursday, Earl will be farther away, the wind shear will be lessened, and 97L will have had enough time over water to potentially be a hurricane. Depending upon how fast they have 97L moving, the computer models have a wide variety of solutions for 97L, ranging from a making it a major hurricane five days from now (GFDL model) to a weak tropical storm five days from now (several models.) History suggests that a storm in 97L's current location has a 20% chance of making landfall on the U.S. East Coast. NHC is giving 97L a 80% chance of developing into a tropical depression by Monday.


Figure 3. Morning satellite image of 97L.

Elsewhere in the Tropics
In the Eastern Pacific, Tropical Depression Frank is dissipating off the coast of Baja California in Mexico.

There is at least one more tropical wave over Africa that will be a candidate to develop into a tropical depression late next week once it emerges from the coast.

Jeff Masters

Hurricane

Updated: 3:54 PM GMT on August 28, 2010

Permalink

Danielle a Cat 4; Earl more organized; Northwest Passage opens for 4th year in a row

By: JeffMasters, 3:20 PM GMT on August 27, 2010

The Atlantic's first major hurricane of 2010, Hurricane Danielle, has arrived. Danielle finished a steady round of intensification early this morning, peaking as a low-end Category 4 storm with 135 mph winds. Infrared satellite loops show little change in Danielle's intensity over the past 12 hours, and the hurricane may be at its peak intensity. Wind shear remains low, 5 - 10 knots, and sea surface temperatures of 29°C are still warm enough to support some modest additional intensification, though. The first Hurricane Hunter mission is scheduled to investigate Danielle this afternoon, and we'll get a better idea of Danielle's strength then.


Figure 1. True color image of Danielle taken at 12:55pm EDT Thursday, August 26, 2010, by NASA's Aqua satellite.

Intensity forecast for Danielle
The latest SHIPS model forecast predicts that shear will remain low, 5 - 10 knots, through Saturday night, but then rapidly rise to a high 25 - 50 knots Sunday through Tuesday when Danielle encounters strong upper-level winds from a trough of low pressure. Danielle may go through an eyewall replacement cycle today or Saturday, which could weaken the storm to Category 2 strength. More substantial weakening will occur on Sunday, when Danielle encounters the high shear.

Track forecast for Danielle
Danielle wandered off of its northwesterly path over the past few hours and has headed almost due west, but the hurricane should resume a more northwesterly path shortly. A trough of low pressure that is currently moving off the East Coast of the U.S. and Canada should begin pulling Danielle due north Saturday, with the hurricane passing east of Bermuda Saturday night through Sunday. NHC is giving Bermuda just a 12% chance of getting tropical storm force winds of 39 mph or greater from Danielle, and no chance of getting winds 58 mph or greater. The Bermuda Weather Service is predicting 10 - 18 foot waves this weekend for Bermuda's offshore waters. All of the computer models agree on recurvature of Danielle out to sea on Sunday, with the storm missing both Bermuda and Canada. The latest wave forecast from NOAA's Wavewatch III model (which uses the GFS model as its prediction for the position and intensity of hurricanes), calls for waves from Danielle to begin hitting the coast of North Carolina on Saturday. These waves will build to 6 - 9 feet in the offshore waters from Northern Florida to North Carolina by Sunday. The latest near shore water forecast for Cape Hatteras calls for 6 - 8 foot waves Saturday, and 6 - 9 feet on Sunday.


Figure 2. Morning satellite image of Earl.

Tropical Storm Earl
Tropical Storm Earl continues to follow a track very similar to Danielles across the mid-Atlantic. The wind shear analysis from the University of Wisconsin CIMSS group shows low shear of 5 - 10 knots over Earl, and recent satellite imagery shows the storm is slowly growing more organized. More low-level spiral bands have developed this morning, and the storm has assumed a more circular shape. Water vapor satellite images show a large region of dry air from the Sahara lies to the west of Earl, and this dry air will likely be the primary inhibiting factor for development over the next few days. Sea surface temperatures are warm, around 28°C. Earl is too far from land for the Hurricane Hunters to reach, and the first flight into the storm is scheduled for Saturday evening.

Forecast for Earl
The latest SHIPS model forecast for Earl predicts that wind shear will remain low to moderate, 5 - 15 knots, for the next five days. There is a possibility, though, that Earl may see higher shear Saturday night through Sunday, due to strong upper-level winds from the outflow of Hurricane Danielle. SSTs will steadily warm from 28°C on Friday to almost 30°C by Sunday beneath Earl. The storm may cross Danielle's cold water wake at some point, which could interrupt development. Dry air will probably be the main inhibiting factor for Earl over the next three days, though. In combination, these factors should allow for intensification of Earl into a hurricane 3 - 4 days from now. An unknown wild card in this may be the possible interaction with 97L. Several models predict 97L will grow to hurricane strength and move faster than Earl. It is possible the storms could interfere with each other, or have some counterclockwise rotation around a common center, 4 - 6 days from now.

History suggests that a storm in Earl's current location has a 15 - 20% chance of making landfall on the U.S. East Coast, but the long term fate of Earl remains unclear. The storm is being steered by the same ridge of high pressure steering Danielle, and Earl will initially follow a track similar to Danielle. As Earl approaches the central Atlantic 3 - 4 days from now, the storm will encounter a break in the region of high pressure steering it, courtesy of Danielle. This should give enough of a northwestward motion to the storm so that it misses the Lesser Antilles Islands. Earl would then likely continue northwest towards Bermuda. However, if Danielle recurves out to sea faster than expected, this ridge may have time to build back enough to steer Earl over the northern Lesser Antilles Islands. NHC is giving Saint Maarten in the northern Lesser Antilles a 35% chance of receiving tropical storm force winds from Earl, and a 8% chance of getting hurricane force winds.


Figure 3. Morning satellite image of 97L.

97L
It's deja-vu all over again, as a new tropical wave (Invest 97L) off the coast of Africa, south of the Cape Verdes Islands, appears destined to develop into a tropical storm and follow the path of Danielle and Earl. 97L already has a broad, elongated surface circulation, as seen on satellite loops, but only limited heavy thunderstorm activity. The storm is experiencing a moderate 10 - 20 knots of winds shear, is over warm 28°C waters, and is battling a region of dry air associated with the Saharan Air Layer (SAL) to its northwest. The latest SHIPS model forecast calls for shear to drop to the low range, 5 - 10 knots, Saturday through Sunday, and this should allow 97L to organize into a tropical depression. The storm will follow a track very similar to Danielle and Earl westward towards the Lesser Antilles Islands, and the storm should arrive near the northern Lesser Antilles 5 - 6 days from now. A more northwesterly path is likely for 97L as it approaches the Lesser Antilles, as the storm follows a break in the high pressure ridge steering it, created by Danielle and Earl. It currently appears that the Northern Lesser Antilles Islands may be at risk of at least a close brush with 97L, though. Most of the computer models develop 97L into a hurricane five days from now. However, the storm will have to contend with the cold water wakes left behind by both Danielle and Earl. Furthermore, the GFS model is indicating that 4 - 5 days from now, Earl will be a strong hurricane whose upper-level outflow will create high wind shear of 20 - 30 knots over 97L, weakening it. History suggests that a storm in 97L's current location has a 15 - 20% chance of making landfall on the U.S. East Coast. NHC is giving 97L a 70% chance of developing into a tropical depression by Sunday.

Elsewhere in the Tropics
In the Eastern Pacific, Hurricane Frank is headed towards Baja California in Mexico, but is expected to dissipate before getting there.

There are more tropical waves over Africa that will be candidates to develop next week once they emerge over the Atlantic. In particular, a wave near 10N 20E has an impressive circulation.

The Northwest and Northeast Passages are open
The Northwest Passage--the legendary shipping route through ice-choked Canadian waters at the top of the world--melted free of ice last week, and is now open for navigation, according to satellite mosaics available from the National Snow and Ice Data Center and The University of Illinois Cryosphere Today. This summer marks the fourth consecutive year--and fourth time in recorded history--that the fabled passage has opened for navigation. Over the past four days, warm temperatures and southerly winds over Siberia have also led to intermittent opening of the Northeast Passage, the shipping route along the north coast of Russia through the Arctic Ocean. It is now possible to completely circumnavigate the Arctic Ocean in ice-free waters, and this will probably be the case for at least a month. This year marks the third consecutive year--and the third time in recorded history--that both the Northwest Passage and Northeast Passage have melted free, according to the National Snow and Ice Data Center. The Northeast Passage opened for the first time in recorded history in 2005, and the Northwest Passage in 2007. It now appears that the opening of one or both of these northern passages is the new norm, and business interests are taking note--commercial shipping in the Arctic is on the increase, and there is increasing interest in oil drilling. The great polar explorers of past centuries would be astounded at how the Arctic has changed in the 21st century.


Figure 4. Arctic sea ice extent image for August 24, 2010, as compiled by The University of Illinois Cryosphere Today. The northern route (Western Parry Channel) through the Northwest Passage was completely clear of ice, as was the Northeast Passage. The southern route through the Northwest Passage was still partially blocked.

What caused the opening of the Northwest and Northeast Passages?
The remarkable thinning of Arctic sea ice in recent years has left behind a very thin layer of mostly 1-year old ice in the Arctic, highly vulnerable to rapid melting. As I describe in detail in wunderground's sea ice page, this thinning was mostly due to natural wind pattern in the 1990s, much warmer than average ocean waters invading the Arctic from both the Pacific and Atlantic Oceans, very warm air temperatures, and deposition of black soot from fires used to clear agricultural land in Europe and air pollution originating in industrialized regions of the Northern Hemisphere. This year, Canada experienced its warmest winter in history, and record warm temperatures were observed during spring over the Western Canadian Arctic. Spring 2010 was the warmest in the region since 1948; some regions of the Western Canadian Arctic were more than 6°C (11°F) above average. These warm conditions helped break the ice up early in the Northwest Passage. Warm conditions continued this summer over both the Northwest and Northeast Passages, with temperatures averaging 1 - 2°C above average over the majority of the region. As observed in previous years, contributing to this year's melt was the presence of much warmer than average ocean waters invading the Arctic from both the Pacific and Atlantic Oceans, and the deposition of black soot on the ice, which absorbs sunlight and heats up the ice. Lack of sunshine and natural wind patterns this summer helped counteract the melting, though, compared to the record melt year of 2007. Still, 2010 is on track come in 2nd or 3rd place for the lowest summertime Arctic sea ice extent on record. The past six years have had the six lowest Arctic ice extents on record, and this summer's melting season took a huge toll on the amount of thick, multi-year old ice, according to the National Snow and Ice Data Center. Modeling results from the University of Washington Polar Science Center (Figure 5) suggest that the volume of Arctic sea ice is at a record low for this time of year. The loss of so much old, thick ice this year makes it increasing likely that Arctic sea ice will suffer a record retreat that surpasses 2007's, sometime in the next ten years. We are still on track to see the Arctic sea ice completely disappear in summer by 2030, as predicted by a number of Arctic sea ice experts.


Figure 5. Arctic sea ice volume as computed by the PIOMAS model of the University of Washington Polar Science Center.

When was the last time the Northwest and Northeast Passages melted free 3 consecutive years?
The first recorded attempt to find and sail the Northwest Passage occurred in 1497, and ended in failure. The thick ice choking the waterways thwarted all attempts at passage for the next four centuries. While we cannot say for certain the Northwest Passage did not open between 1497 and 1900, it is highly unlikely that a string of three consecutive summers where both the Northwest and Northeast Passage opened would have escaped the notice of early mariners and whalers, who were very active in northern waters. We can be sure the Northern Passages were never open between 1900 - 2005, as we have detailed ice edge records from ships (Walsh and Chapman, 2001). A very cold period dominated northern latitudes during the 1600s, 1700s, and 1800s, known as "The Little Ice Age", further arguing against an opening of the Northern Passages during those centuries. The Northern Passages may have been open at some period during the Medieval Warm Period, between 900 and 1300 AD. Temperatures in Europe were similar, though probably a little cooler, than present-day temperatures. However, the Medieval Warm Period warmth was not global, and it is questionable whether or not sections of the Northern Passages along the Alaskan, Canadian, and Russian shores shared in the warmth of the Medieval Warm Period. So, a better candidate for the last previous multi-year opening of the Northern Passages was the period 6,000 - 8,500 years ago, when the Earth's orbital variations brought more sunlight to the Arctic in summer than at present. Funder and Kjaer (2007) found extensive systems of wave generated beach ridges along the North Greenland coast that suggested the Arctic Ocean was ice-free in the summer for over 1,000 years during that period. Prior to that, the next likely time the Northern Passages were open was during the last inter-glacial period, 120,000 years ago. Arctic temperatures then were 2 - 3 degrees Centigrade higher than present-day temperatures, and sea levels were 4 - 6 meters higher. It is possible we'll know better soon. A new technique that examines organic compounds left behind in Arctic sediments by diatoms that live in sea ice give hope that a detailed record of sea ice extent extending back to the end of the Ice Age 12,000 years ago may be possible (Belt et al., 2007). The researchers are studying sediments along the Northwest Passage in hopes of being able to determine when the Passage was last open.

But Antarctic sea ice is at a record high!
Climate change contrarians like to diminish the importance of Arctic sea ice loss by pointing out that in recent years, Antarctic sea ice extent has hit several record highs, including in July of 2010. They fail to mention, though, the fact that ocean temperatures in the Antarctic sea ice region have warmed significantly in recent decades--and faster than the global average temperature rise! So how can sea ice increase when ocean temperatures are warming so dramatically? This topic is discussed in detail by one of my favorite bloggers, physicist John Cook over at skepticalscience.com. In his words:

"There are several contributing factors. One is the drop in ozone levels over Antarctica. The hole in the ozone layer above the South Pole has caused cooling in the stratosphere (Gillet 2003). A side-effect is a strengthening of the cyclonic winds that circle the Antarctic continent (Thompson 2002). The wind pushes sea ice around, creating areas of open water known as polynyas. More polynyas leads to increased sea ice production (Turner 2009).

Another contributor is changes in ocean circulation. The Southern Ocean consists of a layer of cold water near the surface and a layer of warmer water below. Water from the warmer layer rises up to the surface, melting sea ice. However, as air temperatures warm, the amount of rain and snowfall also increases. This freshens the surface waters, leading to a surface layer less dense than the saltier, warmer water below. The layers become more stratified and mix less. Less heat is transported upwards from the deeper, warmer layer. Hence less sea ice is melted (Zhang 2007). "


This counter-intuitive result shows how complicated our climate system is. Climate change contrarians are masters at obscuring the truth by taking counter-intuitive climate events like this out of context, and twisting them into a warped but believable non-scientific narrative. Lawmakers tend to hear a lot of these narratives, since the lobbying wings of the oil and gas industry spent $175 million last year to help convince Congress not to regulate their industry. This number does not include the tens of millions more spent by the U.S. Chamber of Commerce, National Association of Manufacturers, coal industry, and other business interests intent upon stymying legislation that might cut into profits of the oil, coal, and gas industry. For comparison, the lobbying money spent by environmental groups in 2009 was approximately $22.5 million. Spending for PR efforts aimed at influencing opinion on climate change issues probably has a similar disparity. This is a major reason why you may have heard, "Hey, Antarctic sea ice is increasing, so why worry about Arctic sea ice loss?"

Commentary
Diminishing the importance of Arctic sea ice loss by calling attention to Antarctic sea ice gain is like telling someone to ignore the fire smoldering in their attic, and instead go appreciate the coolness of the basement, because there is no fire there. Planet Earth's attic is on fire. This fire is almost certain to grow much worse. When the summertime Arctic sea ice starts melting completely a few years or decades hence, the Arctic will warm rapidly, potentially leading to large releases of methane gas stored in permafrost and in undersea "methane ice" deposits. Methane is 20 - 25 times more potent than CO2 at warming the climate, meaning that the fire in Earth's attic will inexorably spread to the rest of the globe. To deny that the fire exists, or that the fire is natural, or that the fire is too expensive to fight are all falsehoods. This fire requires our immediate and urgent attention. Volunteer efforts to fight the fire by burning less coal, oil, and gas are laudable, but insufficient. It's like trying to fight a 3-alarm blaze with a garden hose. Every time you reduce your use of oil, gas, or coal, you make the price of those fuels cheaper, encouraging someone else to burn them. Global warming will not slow down until Big Government puts a price on oil, coal and gas--a price that starts out low but increases every year. This can be done via emissions trading, a "fee and dividend" approach, or other means. People are rightfully mistrustful of the ability of Big Government to solve problems, but we don't have a choice. The alternative is to geoengineer our climate--an extremely risky solution. It is time to pay the big bucks and send out the fire engines, before the conflagration gets totally out of control. Consider the Great Russian Heat Wave of 2010 and the Pakistani floods of 2010 a warning. These sorts of extreme events will grow far more common in the decades to come, because of human-caused climate change.

References
Belt, S.T., G. Masse, S.J. Rowland, M. Poulin, C. Michel, and B. LeBlanc, "A novel chemical fossil of palaeo sea ice: IP25", Organic Geochemistry, Volume 38, Issue 1, January 2007, Pages 16-27.

Funder, S. and K.H. Kjaer, 2007, "A sea-ice free Arctic Ocean?", Geophys. Res. Abstr. 9 (2007), p. 07815.

Walsh, J.E and W.L.Chapman, 2001, "Twentieth-century sea ice variations from observational data", Annals of Glaciology, 33, Number 1, January 2001 , pp. 444-448.

Zhang, J.L., 2006, "Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions", Journal of Climate 20, Number 11, pp 2515-2529.

The Manufactured Doubt Industry and the hacked email controversy, a blog post I did in November 2009.

Jeff Masters

Hurricane

Updated: 3:38 PM GMT on August 27, 2010

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Danielle steams towards Bermuda; Earl organizing over eastern Atlantic

By: JeffMasters, 3:20 PM GMT on August 26, 2010

Hurricane Danielle continues on its steady northwesterly path towards Bermuda, as a respectable Category 2 hurricane with 105 mph winds. However, the hurricane has had its troubles this morning--Danielle wrapped a significant amount of dry air into its core between 4am - 8am EDT this morning, and Infrared satellite loops show that Danielle's cloud tops warmed late this morning, indicating that this dry air reduced the vigor of Danielle's thunderstorms. Danielle has managed to quickly mix out most of this dry air and reform its broken eyewall early this afternoon, as seen on recent visible satellite imagery (Figure 1.) We'll get a better idea of Danielle's intensity on Friday afternoon, when the first Hurricane Hunter mission is scheduled. The storm is still too far from land to reach with their airplanes today.


Figure 1. Morning satellite image of Danielle. A huge thunderstorm has blown up on the west side of the eyewall, giving the hurricane a rather lopsided appearance.

Intensity forecast for Danielle
Once Danielle recovers from its current troubles with dry air, warm 29°C SSTs combined with low wind shear of 5 - 10 knots should allow the storm to intensify. There is substantial dry air to the west and south of Danielle, though, and it is quite possible that some unexpected increase in shear could inject dry air into the hurricane at any time over the next few days. The latest SHIPS model forecast predicts that this shear will remain low, 5 - 10 knots, over the next three days, but then rapidly rise to a high 20 - 40 knots on Sunday. Danielle will probably reach peak intensity Saturday night or Sunday morning, near the time of its closest approach to Bermuda. NHC is giving Danielle a 41% chance of becoming a major Category 3 hurricane.

Track forecast for Danielle
On Saturday, a trough of low pressure that is expected to move off the East Coast of the U.S. and Canada should begin pulling Danielle due north, with the hurricane passing east of Bermuda Saturday night through Sunday. NHC is giving Bermuda a 25% chance of receiving tropical storm force winds of 39 mph or greater from Danielle, and a 1% chance of getting hurricane force winds. This is a substantial reduction from the odds given in the 5am forecast, which were 37% and 6%, respectively. The Bermuda Weather Service is predicting 15 - 20 foot waves this weekend for Bermuda's offshore waters. The most likely scenario once Danielle passes north of Bermuda is for the storm to recurve out to sea, missing the U.S. and Canadian coasts. All of the computer models currently call for this scenario. The possibility of Danielle stalling north of Bermuda and potentially tracking northwest towards the U.S. and Canadian coasts, as called for by the NOGAPS model in some of its runs yesterday, is looking less likely.

History suggests that a storm in Danielle's current location has only a 5 - 10% chance of making landfall on the U.S. East Coast. If Danielle passes east of Bermuda, as forecast, these percentages drop to less than 5%. However, Danielle will bring high surf conditions to the U.S. East Coast beginning this weekend. The latest wave forecast from NOAA's Wavewatch III model (which uses the GFS model as its prediction for the position and intensity of hurricanes), calls for waves from Danielle to begin hitting the coast of North Carolina on Saturday. These waves will build to 7 - 10 feet in the offshore waters from Northern Florida to North Carolina by Sunday. The latest near shore water forecast for Cape Hatteras calls for 5 - 8 foot waves Saturday, and 7 - 10 feet on Sunday.


Figure 1. Morning satellite image of Danielle, Earl, and a new tropical wave emerging from the coast of Africa (possibly to be designated 97L?)

Tropical Storm Earl
Tropical Storm Earl developed late yesterday afternoon, one week ahead of when climatology suggests the fifth named storm of the year should occur in the Atlantic. Earl is currently very weak and ragged looking, thanks to dry air and wind shear. The wind shear analysis from the University of Wisconsin CIMSS group shows an upper level trough of low pressure to the north of Earl is bringing a high 20 - 30 knots of wind shear to the northern portion of the storm, though the center of Earl is under low wind shear of 5 - 10 knots. The shear has injected dry air into the storm, disrupting the circulation. As a result, Earl has a rather disorganized clumpy appearance on satellite imagery, and the center jumped 30 miles to the south this morning to reposition itself farther from the shear, and closer to the main region of heavy thunderstorms. Water vapor satellite images show a large region of dry air from the Sahara lies to the west of Earl, and this dry air will likely be the primary inhibiting factor for development over the next three days. Sea surface temperatures are warm, around 28°C. Earl is too far from land for the Hurricane Hunters to reach, and the first flight into the storm is not scheduled until Sunday afternoon.

Forecast for Earl
Wind shear is predicted to remain low to moderate, 5 - 15 knots, for the next five days. SSTs will steadily warm--to 28°C on Friday, and 29°C by Sunday. Earl may cross Danielle's cold water wake at some point, which could interrupt development. Dry air will probably be the main inhibiting factor for Earl over the next three days. In combination, these factors should allow for a slow intensification of Earl into a hurricane 4 - 5 days from now.

History suggests that a storm in Earl's current location has a 15 - 20% chance of making landfall on the U.S. East Coast, but the long term fate of Earl remains unclear. The storm is being steered by the same ridge of high pressure steering Danielle, and Earl will initially follow a track similar to Danielle's. As Earl enters the central Atlantic 4 - 5 days from now, the storm will encounter the same mid-Atlantic trough that is steering Danielle to the north. This trough should be able to turn Earl far enough to the northwest so that the storm will miss the Lesser Antilles Islands. It is unclear at this point whether this trough will be strong enough to fully recurve Earl out to sea, east of Bermuda. The long range 6 - 10 day forecasts from the GFS and ECMWF models have consistently been calling for Earl to turn north and follow Danielle, bringing Earl very close to Bermuda next week. This is a reasonable forecast, since Danielle is large enough and strong enough to create a low pressure "path of least resistance" for Earl to follow northwestward towards Bermuda.

Elsewhere in the Tropics
A new tropical wave emerged from the coast of Africa yesterday, and has the potential to develop into a tropical depression early next week. Several of the computer models develop this wave 3 - 6 days from now, and I can't see any reason why this would not occur. Conditions for tropical cyclone development will remain favorable in the Eastern Atlantic for at least the next week, and several of these models successfully predicted the development of both Danielle and Earl well in advance. The new wave will follow a track similar to that of Danielle and Earl, with an unknown potential for eventually affecting any land areas.

In the Eastern Pacific, Hurricane Frank has moved away away from the Mexican coast, and does not appear to be a threat to bring heavy rains to Mexico.

Jeff Masters

Hurricane

Updated: 11:12 PM GMT on August 17, 2011

Permalink

Little change to Danielle; TD 7 forms; flood waters peak in southern Pakistan

By: JeffMasters, 3:15 PM GMT on August 25, 2010

Hurricane Danielle has changed little in organization over the past 12 hours, and is having trouble with strong upper level westerly winds that are creating a moderate 15 - 20 knots of wind shear. Latest satellite loops show that most of Danielle's low level spiral bands are on the east side of the storm, away from the shear. There is also a considerable amount of dry air on the west side of the storm that is inhibiting thunderstorm formation on the hurricane's west side. Danielle is over warm 28°C water. The Hurricane Hunters will begin flying missions into Danielle on Friday afternoon, since the storm is still too far from land to reach with their airplanes.


Figure 1. Morning satellite image of Danielle, Tropical Depression Seven, and a new tropical wave emerging from the coast of Africa (possibly to be designated 97L?)

Intensity forecast for Danielle
In the short term, now through Thursday, persistent wind shear of 15 - 20 knots due to strong upper level winds out of the west should keep any intensification of Danielle slow. The latest wind shear forecast from the SHIPS model calls for shear to fall to the low range, 5 - 10 knots, Friday through Saturday. With SSTs expected to be a warm 28 - 29°C, these conditions may favor a bout of rapid intensification. It is possible Danielle could become a major Category 3 hurricane by Saturday night and Sunday, when it should be making its closest approach to Bermuda.

Track forecast for Danielle
The trough of low pressure over the mid-Atlantic Ocean steering Danielle more to the northwest will wane in influence over the next two days, as a ridge of high pressure moves north of the storm. This will keep Danielle moving generally northwest towards Bermuda over the next three days. On Saturday, a new trough of low pressure that is expected to move off the East Coast of the U.S. and Canada should begin pulling Danielle due north, eventually recurving the storm out to sea without hitting land. However, one model--the NOGAPS--predicts that Danielle will be moving too slowly and that the new trough will not be strong enough to recurve Danielle out to sea. The NOGAPS keeps Danielle moving on a northwest course, passing very close to Bermuda, and coming perilously close the Northeast U.S. coast 7 - 8 days from now. The NOGAPS is an outlier in the models, and the official NHC forecast follows the consensus of our other reliable models, calling for Danielle to turn towards the north this weekend and miss Bermuda. These models include the three best-performing models from last year at making 4 - 5 day forecasts--the Canadian, ECMWF, and GFS models. Assuming Danielle follows the official NHC track, Bermuda can expect the storm's outer winds to reach the island Saturday night. NHC is giving Bermuda a 39% chance of receiving tropical storm force winds of 39 mph or greater from Danielle, and a 9% chance of getting hurricane force winds.

History suggests that a storm in Danielle's current location has only a 15% chance of making landfall on the U.S. East Coast. If Danielle passes east of Bermuda, as forecast, these percentages drop to less than 5%. However, Danielle will bring high surf conditions to the U.S. East Coast beginning this weekend. The latest wave forecast from NOAA's Wavewatch III model (which uses the GFS model as its prediction for the position and intensity of hurricanes), calls for waves from Danielle to begin hitting the coast of North Carolina on Saturday. These waves will build to 6 - 9 feet in the offshore waters from Northern Florida to North Carolina by Sunday. The latest nearshore water forecast for Cape Hatteras calls for 5 - 8 foot waves Saturday through Sunday. Waves will be much higher in Bermuda, where the Bermuda Weather Service is predicting 10 - 15 foot waves this weekend.


Figure 2. Wave forecast for the Atlantic made by NOAA's Wavewatch III model for Sunday morning, August 29, 2010. The model was run at 2am EDT Wednesday, August 25. The model is predicting that waves from Danielle of 2 - 3 meters (6 - 9 feet) will begin affecting the offshore waters from northern Florida to Cape Hatteras, North Carolina, on Sunday. These waves will cause considerable beach erosion and dangerous rip currents.

Tropical Depression Seven
Satellite images show that the tropical wave (96L) that emerged off the coast of Africa Monday has become Tropical Depression Seven. Satellite estimates of TD 7's strength support calling this a 35 mph tropical depression, and latest satellite loops show a well-organized system with an increasing amount of heavy thunderstorm activity, plenty of low-level spiral banding, and expanding upper-level outflow to the north. This is likely to be Tropical Storm Earl later today. Tropical Depression Seven is now well east of the Cape Verdes Islands, and has a large stretch of open ocean before it. Water vapor satellite images show a large region of dry air from the Sahara lies to the west of TD 7, and this dry air will likely be the primary inhibiting factor for development over the next three days. Wind shear is low, 5 - 10 knots, and sea surface temperatures are warm, around 28°C.

Forecast for Tropical Depression Seven
Wind shear is predicted to remain low, 5 - 10 knots, for the next three days. SSTs will cool a bit to 27.5°C by Thursday, but this is still above the 26.5°C threshold for hurricane development. TD 7 may cross Danielle's cold water wake at some point, which may interrupt development. Dry air will probably be the main inhibiting factor for TD 7 over the next three days. The SHIPS model is indicating an increase in wind shear to the moderate range, 10 - 20 knots, 4 - 5 days from now. In combination, these factors should allow for a slow intensification of TD 7 into Hurricane Earl 4 -5 days from now.

The long range fate of TD 7 remains unclear. The storm is being steering by the same ridge of high pressure steering Danielle, and will initially follow a track similar to Danielle. As TD 7 approaches the central Atlantic 4 - 6 days from now, the storm will encounter the same mid-Atlantic trough that is expected to turn Danielle to the north. This trough should be able to turn TD 7 far enough to the northwest so that it will miss the Lesser Antilles Islands. However, it is unclear at this point whether this trough will be strong enough to fully recurve TD 7 out to sea, east of Bermuda. This will, in part, depend upon how strong Danielle gets and how fast it moves. A stronger Danielle is likely to create more of a break in the ridge of high pressure steering TD 7, encouraging the storm to turn north and recurve out to sea. A weaker Danielle will make TD 7 more likely to miss recurvature, and follow a track to the west or west-northwest towards the U.S. East Coast early next week. History suggests that a storm in TD 7's current location has only a 20% chance of making landfall on the U.S. East Coast.

Elsewhere in the Tropics
A new tropical wave is emerging from the coast of Africa this morning (Figure 1.) The latest GFS model run develops this wave into a tropical depression 3 - 4 days from now. I can't see any reason why this would not occur. Conditions for tropical cyclone development will remain favorable in the Eastern Atlantic for at least the next week, and the GFS models has successfully predicted the development of both Danielle and TD 7 over the past two weeks. This new wave probably has a better chance of hitting the U.S. East Coast than either Danielle or TD 7.

Over in the Gulf of Mexico, a trough of low pressure is generating some disorganized thunderstorm activity. This action may increase on Thursday and Friday, when a cold front is expected to move off the coast of Texas and over the Gulf. NHC is giving a 10% chance of this area of disturbed weather developing into a tropical depression by Friday. Any storm that might develop over the Gulf of Mexico from this disturbance would likely not stay over water long enough to develop into a hurricane, and none of the computer models currently support tropical cyclone development in the Gulf over the next seven days.

In the Eastern Pacific, Tropical Storm Frank has moved away the coast far enough from the Mexican coast to no longer pose a heavy rainfall threat, and all tropical storm warnings have been dropped.

Flood waters peak in southern Pakistan
Flooding on Pakistan's largest river, the Indus, has peaked at the 2nd highest flow rates on record today at the Indus River gauge station nearest to the coast, at Kotri. Today's flow rate was 938,000 cubic feet/sec, and the record, set in 1956, was 980,000 cubic feet/sec. The new flooding has forced new evacuations of hundreds of thousands of people in southern Pakistan over the past four days. Flood heights at every monitoring station along the Indus have been the highest or almost the highest since records began in 1947. Flooding has slowly eased along the upper and middle stretches of the Indus where most of the heavy monsoon rains fell in late July and early August, though most of the flooded regions remain underwater and 800,000 people are still cut off from receiving aid.

More rain is in the forecast, and flood waters will only gradually subside in coming weeks. The monsoon is currently in an active phase, and is being enhanced by a low pressure system passing over the northern portion of the country. Rainfall will be moderate to heavy in some of the flooded regions over the next two days, according to the Pakistan Meteorological Department.


Figure 3. Flood volumes on Pakistan's main river, the Indus, during August 2010. Flood height have generally been declining in recent weeks along most of the Indus, but are peaking right now near the coast. Image credit: Pakistan Meteorology Department.


Figure 4. Image of the Pakistan flood catastrophe of 2010, courtesy of the Pakistan Meteorology Department.

The toll in Pakistan is staggering: 1,600 dead, 1.2 million homes destroyed, 800,000 stranded and cut off from supplies, 4 million homeless, and 1.6 million already affected by water-borne diseases such as cholera and dysentery. Some aid agencies helping with humanitarian crisis in Pakistan:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

Jeff Masters

Hurricane

Permalink

Danielle a hurricane; TD 7 forming off coast of Africa

By: JeffMasters, 2:18 PM GMT on August 24, 2010

Hurricane Danielle has stopped intensifying and is now looking a bit ragged this morning, but remains a respectable Category 1 hurricane with 80 mph winds. The intensity of Danielle's heavy thunderstorms has waned in the past few hours, and the organization of the storm is less impressive. This is probably due do strong upper-level winds out of the west that are creating a moderate 10 - 20 knots of wind shear, and injecting some of the dry air from the Saharan Air Layer (SAL) that surrounds Danielle. Danielle is over warm 28°C water, but is far from any land areas.


Figure 1. Morning satellite image of Tropical Storm Danielle (left side of image) and the forming Tropical Depression Seven (right side of image.)

Forecast for Danielle
A powerful trough of low pressure over the mid-Atlantic Ocean will begin to pull Danielle more to the northwest by Wednesday, keeping Danielle well to the east of Bermuda. Most of the models predict that this trough will be strong enough to fully recurve Danielle out to sea. It is possible that Danielle could eventually threaten Newfoundland, Canada, but it currently does not appear that any other land areas will be at risk from this storm. History suggests that a storm in Danielle's current location has only a 20% chance of making landfall on the U.S. East Coast. If Danielle passes east of Bermuda, as forecast, these percentages drop to less than 5%. As far as intensity goes, it is looking unlikely that Danielle will attain major hurricane status (115+ mph winds.) There is enough dry air and wind shear affecting the storm today that it will take several days for the storm to recover its strength, making it less likely the storm can hit Category 3.

The formation of Danielle is remarkable in this it was successfully forecast by the GFS model nearly two weeks in advance. The ECMWF and NOGAPS models also did a good job of predicting Danielle's formation a week in advance. The models are getting better and better each year at forecasting genesis of tropical cyclones, though a successful 1-week forecast of genesis is still a rarity. For example, none of the models foresaw the development of 96L until just 3 - 4 days ago.


Figure 2. Plot showing historically the percent chance of a tropical cyclone in a given location impacting the U.S. East Coast. For storms in Danielle's current position (orange hurricane symbol), about 20% of them go on to hit the U.S. East Coast. For storms in 96L's current location (red circle with a "?" in it), the odds are also 20%. Image credit: Bob Hart, Florida State University.

96L (soon to be Tropical Depression Seven)
Satellite images suggests that a tropical wave (96L) that emerged off the coast of Africa yesterday morning has developed a closed circulation, low-level spiral bands, and an increasing amount of heavy thunderstorms. While this morning's ASCAT pass does not show a clear closed circulation, satellite estimates of 96L's strength support calling this a 30 mph tropical depression. It is likely that this storm will be designated Tropical Depression Seven later today. 96L is already bringing heavy rain and strong, gusty winds to the southern Cape Verde Islands. Winds were sustained at 26 mph at Mindelo in the northwest Cape Verde Islands this morning, and 24 mph at Praia, the station closest to the center of 96L. Both stations were reporting widespread dust, due to strong winds blowing Saharan dust from the coast of Africa. However, water vapor satellite images show that only a modest amount of dry air is accompanying this dust, and dry air is currently not a major detriment to 96L. Wind shear is about 10 - 20 knots, and sea surface temperatures are warm, 28°C.

Forecast for 96L/Tropical Depression Seven
Wind shear is predicted to remain low, 5 - 10 knots, for the next four days. SSTs will cool a bit to 27°C by Thursday, but this is still above the 26.5°C threshold for hurricane development. Dry air will probably be the main inhibiting factor for 96L. Most of the intensity forecast models bring 96L to hurricane strength by four days from now, and this is a reasonable forecast. 96L should become Tropical Storm Earl later today or on Wednesday, and will probably bring sustained winds of 40 mph to the southernmost Cape Verdes Islands tonight and Wednesday.

The long range fate of 96L remains unclear. The storm is being steering by the same ridge of high pressure steering Danielle, and will initially follow a track similar to Danielle. 96L may encounter the cold waters stirred up by Danielle at times this week, inhibiting development. As 96L approaches the central Atlantic five days from now, the storm will encounter the same mid-Atlantic trough that will be steering Danielle, and 96L should turn more to the northwest. It is unclear at this point whether this trough will be strong enough to fully recurve 96L out to sea, east of Bermuda. This will, in part, depend upon how strong Danielle gets. A stronger Danielle is likely to create more of a break in the ridge of high pressure steering 96L, encouraging the storm to turn north and recurve out to sea. A weaker Danielle will make 96L more likely to miss recurvature, and follow a track to the west or west-northwest towards the U.S. East Coast early next week. History suggests that a storm in 96L's current location has only a 20% chance of making landfall on the U.S. East Coast.

When will the Caribbean and Gulf of Mexico get active?
The large scale atmospheric circulation over the Caribbean and Gulf of Mexico currently features relatively dry, stable, sinking air. This is due, in part, to the Madden-Julian oscillation (MJO). The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The latest MJO forecast from the GFS model calls for the wet phase of the MJO to move into the Caribbean during the first week of September. However, keep in mind that forecasts of MJO activity 1 - 2 weeks in advance are not very skillful. The GFS model forecast of MJO activity made two weeks ago did fairly well for the first week, but poorly for the second week of the forecast.

Tropical Storm Frank spares Mexico
Over in the Eastern Pacific, Tropical Storm Frank has moved away the coast far enough from the Mexican coast to no longer pose a heavy rainfall threat, and all tropical storm warnings have been dropped.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. I'll focus on Danielle, Earl, and Frank, and discuss the possibilities of a hyperactive Atlantic hurricane period coming during the first week of September.

Today's show will be 30 - 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

Hurricane

Updated: 7:56 PM GMT on January 03, 2012

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Danielle forms; extreme heat record for Palestine; south Pakistan flooding worsens

By: JeffMasters, 2:23 PM GMT on August 23, 2010

Tropical Storm Danielle is slowly strengthening over the mid-Atlantic Ocean, and appears destined to become a hurricane by Tuesday. However, Danielle is not a threat to any land areas, and will probably only be a concern to shipping interests. Danielle is a classic "Cape Verdes"-type of storm common during the peak part of hurricane season. Cape Verdes-type storms are so named because they form from tropical waves that come off the coast of Africa and pass near the Cape Verdes Islands just west of Africa. Cape Verdes hurricanes are the largest and most dangerous types of hurricane in the Atlantic, since they spend a long time over water have and have of opportunity to reach full maturity. Danielle is over warm 28°C water, is experiencing low wind shear of 5 - 10 knots, and is embedded in a moist environment--conditions which favor intensification into a hurricane by Tuesday.


Figure 1. Morning satellite image of Tropical Storm Danielle (left side of image) and a new tropical wave that emerged from the coast of Africa this morning (right side of image.)

Forecast for Tropical Storm Danielle
A powerful trough of low pressure over the mid-Atlantic Ocean will begin to pull Tropical Storm Danielle more to the northwest by the middle of this week, keeping Danielle well to the east of the Lesser Antilles Islands and Bermuda. Most of the models predict that this trough will be strong enough to fully recurve Danielle out to sea. It is possible that Danielle could eventually threaten Newfoundland, Canada, but is currently does not appear that any other land areas will be at risk from this storm.

Elsewhere in the tropics
A strong tropical wave has moved off the coast of Africa this morning, and has the potential to develop into a tropical depression later this week. Both the ECMWF and NOGAPS models predict this wave will develop into a tropical depression 2 - 3 days from now. NHC is giving this wave a 10% chance of developing into a tropical depression by Wednesday. Wind shear is a moderate 10 - 20 knots in the region, and will decrease as the storm moves away from the coast of Africa.


Figure 2. Microwave satellite image of Tropical Storm Frank off the coast of Mexico at 6:15 am EDT 8/23/10. This image from NASA's Tropical Rainfall Measurement Mission (TRMM) shows that most of Frank's heavy rains were offshore this morning, though an associated tropical disturbance was bringing heavy rains in excess of 1.5 inches per hour (white colors) to the Gulf of Mexico coast between Veracruz and Alvarado, Mexico. Image credit: Navy Research Lab, Monterey.

Tropical Storm Frank may deluge Mexico's Pacific coast
Over in the Eastern Pacific, an 11-day quiet period has ended with the formation of Tropical Storm Frank. Frank is expected to move parallel to the Mexican coast over the next two days, and will bring isolated regions of heavy rain to coastal Mexico. NHC is warning that these rains could accumulate to ten inches in some areas, but there is a good chance that these dangerous flooding rains will remain just offshore. The latest set of computer models have come into better agreement keeping Frank offshore, and it currently appears the the greatest danger to Mexico will come on Tuesday, when the storm is expected to become a hurricane and will be capable of dumping heavy rain on the Acapulco region.

Palestine records its hottest temperature in history
The State of Palestine, the portion of the territories occupied by Israel that declared independence in 1988, recorded its hottest temperature since record keeping began on August 7, 2010, when the temperature hit 51.4°C (124.5°F) at Kibbutz Almog (also called Qalya or Kalya) in the Jordan Valley. The previous record for Palestine was set on June 22, 1942, at the same location.

Palestine was the 4th nation to set an all-time hottest temperature in history record this month, and the 18th to set such a record this year. There has also been one nation (Guinea) that set an all-time coldest temperature in history record this year. Note that many countries, including the U.S., do not recognize Palestine as a nation, though 110 countries do recognize it. Here's the updated list of nations or semi-independent islands or territories that have set all-time heat or cold records this year:

National heat records set in 2010
Palestine, the portion of the territories occupied by Israel that declared independence in 1988, recorded its hottest temperature since record keeping began on August 7, 2010, when the temperature hit 51.4°C (124.5°F) at Kibbutz Almog (also called Qalya or Kalya) in the Jordan Valley. The previous record for Palestine was set on June 22, 1942, at the same location.

Belarus recorded its hottest temperature in its history on August 6, 2010, when the mercury hit 38.7°C (101.7°F) in Gorky. The previous record was 38.0°C (100.4°F) set at Vasiliyevichy on Aug. 20, 1946.

Ukraine tied its record for hottest temperature in its history when the mercury hit 41.3°C (106.3°F) at Lukhansk on August 1, 2010. Ukraine also reached 41.3°C on July 20 and 21, 2007, at Voznesensk.

Cyprus recorded its hottest temperature in its history on August 1, 2010 when the mercury hit 46.6°C (115.9°F) at Lefconica. The old record for Cyprus was 44.4°C (111.9°F) at Lefkosia in August 1956. An older record of 46.6°C from July 1888 was reported from Nicosia, but is of questionable reliability.

Finland recorded its hottest temperature on July 29, 2010, when the mercury hit 99°F (37.2°C) at Joensuu. The old (undisputed) record was 95°F (35°C) at Jyvaskyla on July 9, 1914.

Qatar had its hottest temperature in history on July 14, 2010, when the mercury hit 50.4°C (122.7°F) at Doha Airport.

Russia had its hottest temperature in history on July 11, when the mercury rose to 44.0°C (111.2°F) in Yashkul, Kalmykia Republic, in the European portion of Russia near the Kazakhstan border. The previous hottest temperature in Russia (not including the former Soviet republics) was the 43.8°C (110.8°F) reading measured at Alexander Gaj, Kalmykia Republic, on August 6, 1940. The remarkable heat in Russia this year has not been limited just to the European portion of the country--the Asian portion of Russia also recorded its hottest temperature in history this year, a 42.7°C (108.9°F) reading at Kara, in the Chita Republic on June 24. The 42.3°C (108.1°F) reading on June 25 at Belogorsk, near the Amur River border with China, also beat the old record for the Asian portion of Russia. The previous record for the Asian portion of Russia was 41.7°C (107.1°F) at Aksha on July 21, 2004.

Sudan recorded its hottest temperature in its history on June 25 when the mercury rose to 49.6°C (121.3°F) at Dongola. The previous record was 49.5°C (121.1°F) set in July 1987 in Aba Hamed.

Niger tied its record for hottest day in history on June 22, 2010, when the temperature reached 47.1°C (116.8°F) at Bilma. That record stood for just one day, as Bilma broke the record again on June 23, when the mercury topped out at 48.2°C (118.8°F). The previous record was 47.1°C on May 24, 1998, also at Bilma.

Saudi Arabia had its hottest temperature ever on June 22, 2010, with a reading of 52.0°C (125.6°F) in Jeddah, the second largest city in Saudi Arabia. The previous record was 51.7°C (125.1°F), at Abqaiq, date unknown. The record heat was accompanied by a sandstorm, which caused eight power plants to go offline, resulting in blackouts to several Saudi cities.

Chad had its hottest day in history on June 22, 2010, when the temperature reached 47.6°C (117.7°F) at Faya. The previous record was 47.4°C (117.3°F) at Faya on June 3 and June 9, 1961.

Kuwait recorded its hottest temperature in history on June 15 in Abdaly, according to the Kuwait Met office. The mercury hit 52.6°C (126.7°F). Kuwait's previous all-time hottest temperature was 51.9°C (125.4°F), on July 27,2007, at Abdaly. Temperatures reached 51°C (123.8°F) in the capital of Kuwait City on June 15, 2010.

Iraq had its hottest day in history on June 14, 2010, when the mercury hit 52.0°C (125.6°F) in Basra. Iraq's previous record was 51.7°C (125.1°F) set August 8, 1937, in Ash Shu'aybah.

Pakistan had its hottest temperature in history on May 26, when the mercury hit an astonishing 53.5°C (128.3°F) at the town of MohenjuDaro, according to the Pakistani Meteorological Department. While this temperature reading must be reviewed by the World Meteorological Organization (WMO) for authenticity, not only is the 128.3°F reading the hottest temperature ever recorded in Pakistan, it is the hottest reliably measured temperature ever recorded on the continent of Asia.

Myanmar (Burma) had its hottest temperature in its recorded history on May 12, when the mercury hit 47°C (116.6°F) in Myinmu, according to the Myanmar Department of Meteorology and Hydrology. Myanmar's previous hottest temperature was 45.8°C (114.4°F) at Minbu, Magwe division on May 9, 1998. According to Chris Burt, author of the authoritative weather records book Extreme Weather, the 47°C measured this year is the hottest temperature in Southeast Asia history.

Ascention Island (St. Helena, a U.K. Territory) had its hottest temperature in history on March 25, 2010, when the mercury hit 34.9°C (94.8°C) at Georgetown. The previous record was 34.0°C (93.2°F) at Georgetown in April 2003, exact day unknown.

The Solomon Islands had their hottest temperature in history on February 1, 2010, when the mercury hit 36.1°C (97°F) at Lata Nendo (Ndeni). The previous record for Solomon Islands was 35.6°C (96.0°F) at Honaiara, date unknown.

Colombia had its hottest temperature in history on January 24, 2010, when Puerto Salgar hit 42.3°C (108°F). The previous record was 42.0°C (107.6°F) at El Salto in March 1988 (exact day unknown).

National cold records set in 2010
One nation has set a record for its coldest temperature in history in 2010. Guinea had its coldest temperature in history in January 9, 2010, when the mercury hit 1.4°C (34.5°F) at Mali-ville in the Labe region.

Commentary
The period January - July was the warmest such 7-month period in the planet's history, and temperatures over Earth's land regions were at record highs in May, June, and July, according to the National Climatic Data Center. It is not a surprise that many all-time extreme heat records are being shattered when the planet as a whole is so warm. Global warming "loads the dice" to favor extreme heat events unprecedented in recorded history. In fact, it may be more appropriate to say that global warming adds more spots on the dice--it used to be possible to roll no higher than double sixes, and now it is possible to roll a thirteen.

The year 2010 now has the most national extreme heat records for a single year--eighteen. These nations comprise 19% of the total land area of Earth. This is the largest area of Earth's surface to experience all-time record high temperatures in any single year in the historical record. Looking back at the past decade, which was the hottest decade in the historical record, seventy-five counties set extreme hottest temperature records (33% of all countries.) For comparison, fifteen countries set extreme coldest temperature records over the past ten years (6% of all countries). My source for extreme weather records is the excellent book Extreme Weather by Chris Burt. His new updates (not yet published) remove a number of old disputed records. Keep in mind that the matter of determining extreme records is very difficult, and it is often a judgment call as to whether an old record is reliable or not. For example, one of 2007's fifteen extreme hottest national temperature records (good for 2nd place behind 2010 for most extreme heat records) is for the U.S.--the 129°F recorded at Death Valley that year. Most weather record books list 1913 as the year the hottest temperature in the U.S. occurred, when Greenland Ranch in Death Valley hit 134°F. However, as explained in a recent Weatherwise article, that record is questionable, since it occurred during a sandstorm when hot sand may have wedged against the thermometer, artificially inflating the temperature. Mr. Burt's list of 225 countries with extreme heat records includes islands that are not independent countries, such as Puerto Rico and Greenland. I thank Mr. Burt and weather record researchers Maximiliano Herrera and Howard Rainford for their assistance identifying this year's new extreme temperature records.

Pakistan's monsoon set to enter a heavy phase; Indus River flood crest peaking near the coast
The flooding on Pakistan's largest river, the Indus, has slowly eased along the upper and middle stretches where most of the heavy monsoon rains fell in late July and early August. However, a pulse of flood waters from these heavy rains has arrived at the coast, and flood heights have risen to all-time record levels today at the Indus river gauge station nearest to the coast, Kotri. The new flooding has forced new evacuations of hundreds of thousands of people in southern Pakistan over the past two days. Flood heights at every monitoring station along the Indus have been the highest or almost the highest since records began in 1947. The monsoon has been in a weak to moderate phase over the past three days, but is expected to enter a heavy phase once again Tuesday through Thursday, according to the Pakistan Meteorological Department.


Figure 3. Image of the Pakistan flood catastrophe of 2010, courtesy of the Pakistan Meteorology Department.

Some aid agencies helping with humanitarian crisis in Pakistan:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

Jeff Masters

Hurricane

Updated: 4:05 PM GMT on August 23, 2010

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Tropical Depression Six arrives

By: JeffMasters, 5:14 PM GMT on August 22, 2010

Tropical Storm Tropical Depression Six is here, but it will not be a threat to land for at least the next five days. Tropical Depression Six is a classic "Cape Verdes"-type storm common during the peak part of hurricane season. Cape Verdes-type storms are so named because they form from tropical waves that come off the coast of Africa and pass near the Cape Verdes Islands just west of Africa. Cape Verdes hurricanes are the largest and most dangerous types of hurricane in the Atlantic, since they spend a long time over water have and have of opportunity to reach full maturity. Tropical Depression Six has a ways to go before it becomes a hurricane, as the storm is embedded in a strong easterly flow of wind courtesy of the African Monsoon that is generating a moderately high 15 - 20 knots of wind shear. There is also a tropical disturbance to the northeast of TD 6 that is sucking away some moisture and is interfering with the storm's circulation. Sea Surface Temperatures (SSTs) are a warm 28°C, and the storm is embedded in a moist environment, so wind shear is the primary inhibiting factor for development. The strong east winds imparting the shear are keeping any heavy thunderstorms from developing on the east side of the center of circulation, which is exposed to view in satellite imagery (Figure 1.)


Figure 1. Afternoon satellite image of Tropical Depression Six.

Forecast for Tropical Depression Six
A ridge of high pressure will force Tropical Depression Six to the west-northwest for the next five days, and the system should increase its forward speed from its current 10 mph to 15 mph by Monday night. A powerful trough of low pressure over the mid-Atlantic Ocean will begin to pull Tropical Depression Six more to the northwest late this week, and the storm should pass well to the northeast of the Lesser Antilles Islands. It remains to be seen, however, it this trough will be strong enough to fully recurve Tropical Depression Six out to sea. The GFS predicts that Tropical Depression Six may pass close to Bermuda about eight days from now, and it is also possible that Tropical Depression Six could eventually hit the U.S. East Coast 9 - 15 days from now. However, we have no skill in making these sort of ultra-long range forecasts, and the long-range fate of TD 6 is uncertain.

Elsewhere in the tropics
The ECMWF and NOGAPS models are predicting formation of a tropical depression off the coast of Africa 3 - 4 days from now.

Jeff Masters

Hurricane

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95L growing more organized; Pakistan's Indus River flood peaking downstream

By: JeffMasters, 2:23 PM GMT on August 21, 2010

A tropical wave (Invest 95L) in the far eastern Atlantic about 350 miles southwest of the Cape Verdes Islands has become more organized this morning. Satellite loops show that the wave has some rotation, and heavy thunderstorm activity has increased in recent hours, after a period overnight with little change. Water vapor satellite loops show that there is some dry air to the north of 95L, but this dry air currently appears to be too far away to significantly interfere with development. The main impediment to development is the moderate 10 - 20 knots of wind shear over the system. The shear is forecast to remain in the moderate range through Monday, then decrease. This should allow 95L to develop into a tropical depression Monday or Tuesday. NHC is giving 95L a 30% chance of developing into a tropical depression by Monday morning. With 95L's recent increase in organization, these odds should probably be 50%.


Figure 1. Morning satellite image of 95L.

Forecast for 95L
A ridge of high pressure will force 95L to the west or west-northwest for the next five days, and the system should increase its forward speed from its current 5 - 10 mph to 15 - 20 mph by Monday. A series of two powerful troughs of low pressure are predicted to move off the U.S. East Coast next week and cross the Atlantic; these troughs should be able to pull 95L far enough to the northwest so that it will miss the Lesser Antilles Islands. If 95L stays weak or does not develop in the next five days, as predicted by the NOGAPS model, it has a chance of eventually threatening Bermuda. If 95L develops into a hurricane, as predicted by most of the computer models, it will probably recurve to the east of Bermuda and not threaten any land areas.

Elsewhere in the tropics
The ECMWF model is predicting formation of a tropical depression in the western Gulf of Mexico off the coast of Texas 6 - 7 days from now.

Pakistan's monsoon rains diminish; Indus River flood crest nears the coast
The flooding on Pakistan's largest river, the Indus, has slowly eased along the upper and middle stretches where most of the heavy monsoon rains fell in late July and early August. However, a pulse of flood waters from these heavy rains is headed southwards towards the coast, and flood heights have risen to near all-time record levels today at the Indus River gauge station nearest to the coast, Kotri (Figure 2.) The new flooding has forced the evacuation of an additional 150,000 people in Pakistan today. Flood heights at every monitoring station along the Indus have been the highest or almost the highest since records began in 1947. Fortunately, the monsoon has entered a weak to moderate phase, and heavy rain is not expected over the flood region over the next few days, according to the Pakistan Meteorological Department.


Figure 2. August flow rates along the Indus River, courtesy of the Pakistan Meteorology Department.

Some aid agencies helping with humanitarian crisis in Pakistan:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

Jeff Masters

Flood Hurricane

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95L organizing off coast of Africa; Pakistan's Indus River flood crest nears coast

By: JeffMasters, 3:35 PM GMT on August 20, 2010

A tropical wave in the far eastern Atlantic about 300 miles southwest of the Cape Verdes Islands was designated Invest 95L by NHC this morning. Satellite loops show that the wave has some rotation, and heavy thunderstorm activity is starting to build. The wave is in a moist environment over SSTs that are at near record warmth (28°C). The main impediment to development is the moderate 10 - 20 knots of wind shear over the system. As 95L moves away from Africa, wind shear will decrease, and system will probably develop into a tropical depression by Sunday or Monday. NHC is giving 95L a 40% chance of developing into a tropical depression by Sunday morning.


Figure 1. Morning satellite image of the disturbed region of weather of the coast of Africa, south of the Cape Verdes Islands.

Forecast for 95L
A ridge of high pressure will force 95L to the west or west-northwest for the next five days, and the system should increase its forward speed from its current 5 - 10 mph to 15 - 20 mph by Monday. A series of two powerful troughs of low pressure are predicted to move off the U.S. East Coast next week and cross the Atlantic; these troughs should be able to pull 95L far enough to the northwest so that it will miss the Lesser Antilles Islands. The long term steering current forecast from the GFS model indicates an above-average chance of recurvature of storms approaching the U.S. East Coast through the end of August, followed by a near-average chance of recurvature for the first week of September.

Elsewhere in the tropics
A tropical wave in the western Caribbean approaching Mexico's Yucatan Peninsula is generating disorganized thunderstorms, and the wave does not have enough time over water to develop into a tropical depression before moving ashore tonight or Saturday.

The ECMWF model is predicting formation of a another tropical depression of the coast of Africa seven days from now. The GFS model predicts a possible subtropical depression may form off the coast of Virginia 5 - 6 days from now and move northeast towards New England.

Pakistan's monsoon rains ease; Indus river flood crest nears the coast
The flooding on Pakistan's largest river, the Indus, has slowly eased along the upper and middle stretches where most of the heavy monsoon rains fell in late July and early August. However, a pulse of flood waters from these heavy rains is headed southwards towards the coast, and flood heights have risen today close to the all-time record for the Indus River gauge station nearest to the coast, Kotri (Figure 2.) Flood heights at nearly every monitoring station along the Indus have set all-time records this month (records go back to 1947.) Fortunately, the monsoon has entered a quiet phase. Little rain is expected over Pakistan over the next 3 - 4 days, according to the Pakistan Meteorological Department.


Figure 2. Flood heights along Pakistan's Indus River during August, 2010. Heavy rains during late July and early August brought record flood height to the upper and middle stretches of the river earlier this month; a wave of flooding progressed downstream, and has now arrived at the monitoring station closest to the coast, Kotri. Image credit: Pakistan Meteorological Department.

The writer of our Climate Change blog, Dr. Ricky Rood, has a sister working in Pakistan, and he is very conversant with the situation there. In his post this week, Pakistan: A Climate Disaster Cast Study, Ricky writes, "We have, here, harsh, brutish reality - a fragile, geopolitically important country where lives, crops, and infrastructure have been washed away. A public health nightmare will follow. We have here a case study of a climate disaster. " In the words of Molly Kinder, a senior policy analyst at the Center for Global Development, who is leading the center's work on a U.S. development strategy for Pakistan, providing aid to Pakistan it is a moral imperative, a humanitarian imperative, and a security imperative.


Figure 3. Image of the Pakistan flood catastrophe of 2010, courtesy of the Pakistan Meteorology Department.

Here are some places that Ricky's sister, Elizabeth, has recommended for donations to help out in the humanitarian crisis in Pakistan:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

Jeff Masters

Flood Hurricane

Updated: 6:05 PM GMT on August 20, 2010

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The Atlantic is quiet; Russian heat wave ends; huge 926 mb South Indian Ocean storm

By: JeffMasters, 2:09 PM GMT on August 19, 2010

A tropical wave in the western Caribbean approaching Mexico's Yucatan Peninsula is generating disorganized thunderstorms. Wind shear is a moderate 10 - 15 knots over the region, and water vapor satellite images show that there is some dry air to the west that will interfere with any development that might occur. None of the reliable computer models develop this wave, and NHC is giving it a 10% chance of developing into a tropical depression.


Figure 1. Morning satellite image of the disturbed region of weather of the coast of Africa, south of the Cape Verdes Islands.

The GFS, NOGAPS, and ECMWF models continue to predict that a tropical storm will form between Africa and the Lesser Antilles Islands sometime in the period 3 - 6 days from now. There is an area of disturbed weather south of the Cape Verdes Islands, but there is no obvious organization to the cloud pattern. Wind shear is a hefty 20 - 30 knots in the region, and the disturbance is a 1 - 2 day journey away from reaching a lower shear area where development can occur. Preliminary indications are that if a storm did develop in this region, it would track west-northwest and pass well to the northeast of the Lesser Antilles Islands 7 - 8 days from now. However, 7-day forecasts of a storm that hasn't even formed yet are not to be trusted.


Figure 2. The cold front that brought an end to the Great Russian Heat Wave of 2010 lies east of Moscow in the NASA MODIS photo taken at 8:35 UTC August 19, 2010. Smoke from wildfires is visible over a wide swath of Russia east of the front. Image credit: NASA.

The Great Russian Heat Wave of 2010 ends
A powerful cold front swept through Russia yesterday and today, finally bringing an end to the Great Russian Heat Wave of 2010. Temperatures at Moscow's Domodedovo airport hit 25°C (77°F) today, which is still 4°C (7°F) above average, but the high temperature since late June. Moscow has seen 62 consecutive days with a high temperature above average, but the latest forecast for Moscow predicts that remarkable string will come to an end Friday, when the high will reach just 17°C (62°F).

Massive 926 mb extratropical storm generating huge waves off Antarctica
One of the most intense extratropical storms in recent years is churning up the waters near the coast of Antarctica in the South Indian Ocean. The powerful storm peaked in intensity yesterday afternoon with a central pressure of 926 mb--the type of pressure typically found in a Category 4 hurricane. Storms this intense form on average once per year, or perhaps less often, according to an email I received from Jeff Callaghan of the Australia Bureau of Meteorology. Since extratropical storms do not form eyewalls, the winds at the surface from this monster storm probably reached "only" 100 - 120 mph (equivalent to a Category 2 or 3 hurricane.) The storm is forecast to generate huge waves with a significant wave height of 13 meters (44 feet) today, according to the NOAA Wavewatch III model (Figure 3.) I have flown into an extratropical storm this intense--in 1989, I participated in a field project based in Maine that intercepted a remarkable extratropical storm that "bombed" into a 928 mb low south of the Canadian Maritime provinces. You can read my story of that somewhat harrowing flight here.


Figure 3. Satellite image taken at 8:10 UTC August 19, 2010, showing the intense extratropical cyclone that has weakened to 940 mb in the South Indian Ocean near the coast of Antarctica. Image credit: NASA.


Figure 4. Surface pressure analysis from 18 UTC August 18, 2010, showing a 926 mb low in the South Indian Ocean, just north of Antarctica. Image credit: Jeff Callaghan, Australia Bureau of Meteorology.


Figure 5. Predicted wave height from the NOAA Wavewatch III model for 2pm EDT (18 UTC) today, August 19, 2010. Peak wave heights of 13 meters (44 feet) are projected over ocean areas between Antarctica and Australia. Long-period waves (19 seconds between crests) up to 7 meters (22 feet) high are predicted to affect the southwest coast of Australia by Sunday. The waves are predicted to propagate eastwards to New Zealand 8 - 9 days from now, and be a respectable 4 - 5 meters high then.

Jeff Masters

Climate Change Hurricane

Updated: 2:10 PM GMT on August 19, 2010

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The Atlantic is quiet; Pakistan monsoon rains continue; last day of Russian heat wave

By: JeffMasters, 1:54 PM GMT on August 18, 2010

A tropical wave in the Caribbean near Jamaica is generating disorganized thunderstorm activity over the central Caribbean. Wind shear is a moderate 10 - 20 knots over the region, and water vapor satellite images show that there is some dry air to the west of Jamaica that will interfere with any development that might occur. None of the reliable computer models develop this wave.

The GFS, NOGAPS, and ECMWF continue to predict that a tropical storm will form between Africa and the Lesser Antilles Islands 3 - 7 days from now. A strong tropical wave currently moving off the coast of Africa is a good candidate for such a development. The NOGAPS model is predicting the development of a strong tropical disturbance near the coast of Honduras this weekend.


Figure 1. Extreme flooding along the Indus River in Pakistan has swollen the river to 16 miles (24 km) wide in sections, as seen in the top image from yesterday. For comparison, and image taken a year ago at this time in August (bottom image) shows that the Indus is normally just 1 - 2 km wide during monsoon season. Image credit: NASA Natural Hazards web site.

Extreme flooding and monsoon rains continue in Pakistan
In flood-ravaged Pakistan, heavy monsoon rains hit the Punjab region in the northeastern portion of the country yesterday, dropping up to 113 mm (4.45") of precipitation. The main river in Pakistan, the Indus, continues to cause extreme flooding, and has expanded to 16 miles (24 km) wide in some sections (Figure 1.) Dr. Ricky Rood, who writes our Climate Change Blog, has a sister that works in Pakistan. He has a must-read analysis of the catastrophe in Pakistan, "Pakistan: A Climate Disaster Case Study".

Moscow hits 93°F on the final day of the Great Russia Heat Wave of 2010
Temperatures at Moscow's Domodedovo airport hit 34°C (93°F) today, which is 13°C (22°F) above average. However, pressures are falling rapidly and winds are picking up out ouf the southwest in advance of a powerful cold front that promises to sweep through all of European Russia tonight, finally bringing an end to the Great Russian Heat Wave of 2010. The latest forecast for Moscow predicts Thursday's high will be just 21°C (69°F)--essentially average. With tonight's cold front will come rain to help put out the fires that continue to plague Russia with toxic smoke. Cool temperatures near of below average over the coming week will also help fire-fighting efforts.

Jeff Masters

Climate Change Hurricane

Updated: 7:09 PM GMT on August 16, 2011

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An active Atlantic hurricane period coming

By: JeffMasters, 1:48 PM GMT on August 17, 2010

The remnants of Tropical Depression Five are no longer a threat, done in by high wind shear and close proximity to land. However, an active period for Atlantic hurricanes is likely for the remainder of August, as the global atmosphere undergoes a major change to the circulation pattern that has dominated Northern Hemisphere weather during July and August. A large trough of low pressure is gathering strength over Europe, and is expected to push eastward. By Thursday, this trough should be able to push away the blocking ridge of high pressure that has given Russia its worst heat wave in history. The shift in circulation has already weakened the large region of sinking air that has brought dry, stable conditions to the tropical Atlantic over the past month. Vertical instability, which was unusually low since late July, has now returned to near normal levels over the tropical Atlantic (Figure 1), though it remains quite low over the rest of the North Atlantic. Instability is measured as the difference in temperature between the surface and the top of the troposphere (the highest altitude that thunderstorm tops can penetrate to.) If the surface is very warm and the top of the troposphere is cold, an unstable atmosphere results, which helps to enhance thunderstorm updrafts and promotes hurricane development. Since SSTs in the Atlantic were at record highs and upper tropospheric temperatures were several degrees cooler than average in July, enhancing instability, something else must have been going on to reduce instability. Dry air can act to reduce instability, and it appears that an unusually dry atmosphere, due to large-scale sinking over the Atlantic, was responsible for the lack of instability. Now that vertical instability has returned to near normal levels, Atlantic hurricane activity should increase to at least average levels over the next two weeks. This is particularly true since SSTs are at record highs and vertical wind shear is at average to below average levels over the tropical Atlantic.


Figure 1. Vertical instability (in °C) over the Caribbean (left) and tropical Atlantic between the Lesser Antilles Islands and coast of Africa (right) in 2010. Normal instability is the black line, and this year's instability levels are in blue. The atmosphere became much more stable than normal in both regions at the end of July. This lack of instability also extended to the Gulf of Mexico and North Atlantic Ocean between Europe and North America. However, in the past few days, vertical instability has returned to normal, thanks to a major pattern shift in the global atmosphere. Image credit: NOAA/CIRA.


Figure 2. The climatology of Atlantic hurricane activity shows a sharp rise in activity around August 18.

Analysis
August 18 historically marks the point where Atlantic hurricane activity makes a major spike upwards (Figure 2.) On average, we can expect to see two named storms and one hurricane during the last half of August. The last half of August usually sees a moistening of the atmosphere off the coast of Africa, as the the African monsoon kicks into high gear. This year is no exception (Figure 3.) The dry Saharan Air Layer (SAL) has retreated to the north, leaving a moist atmosphere conducive for tropical cyclone development off the coast of Africa.

It would not be a surprise to see atmospheric instability increase to above-average levels by early next week as the major atmospheric pattern shift progresses. Will this usher in a hyperactive period of Atlantic hurricane activity next week, with a parade of three or four simultaneous storms strung out across the Atlantic? Probably not, since the Madden-Julian Oscillation (MJO) only marginally favors upward motion over the tropical Atlantic, and is not forecast to change much over the next ten days. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The bottom line: I expect we will see 2 - 3 named storms in the Atlantic by the end of August, including one hurricane. Where these storms might develop and move is difficult to say. It currently appears that the global shift in circulation will bring near-average steering currents to the Atlantic over the next ten days, with a series of troughs of low pressure capable of recurving hurricanes, moving across the Atlantic. The GFS model is indicating, though, that during the few days of August, these troughs may weaken, making recurvature of hurricanes less likely, and increasing the probability of landfalling storms.

The GFS, NOGAPS, and ECMWF currently predict that one or two tropical storms will form between Africa and the Lesser Antilles Islands during the period 4 - 10 days from now. The NOGAPS model is predicting the development of a strong tropical disturbance near the coast of Honduras late this week.


Figure 3. Saharan Air Layer (SAL) analysis shows that the dry air and dust of the SAL (orange colors) lies well to the north of the hurricane breeding grounds off the coast of Africa, near the Cape Verdes Islands. Image credit: University of Wisconsin/NOAA Hurricane Research Division.

Smoke bedeviling Moscow again
Light easterly winds over the past few hours have brought smoke from wildfires back into Moscow today. Temperatures at Moscow's Domodedovo airport hit 29°C (84°F) today, which is 11°C (20°F) above average. The latest forecast for Moscow predicts that just one more day remains for Russia's greatest heat wave in recorded history. On Thursday, a strong trough of low pressure will move through European Russia, finally bringing below average temperatures.

Jeff Masters

Hurricane

Updated: 1:51 PM GMT on August 17, 2010

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ex-TD 5 regenerating; globe has 2nd or 5th warmest July on record

By: JeffMasters, 2:44 PM GMT on August 16, 2010

The remnants of Tropical Depression Five have emerged over the Gulf of Mexico, and the system has enough spin to regenerate into a tropical depression later today or early Tuesday. Latest long range radar out of Mobile, Alabama shows that a band of intense but disorganized thunderstorms lies over the northern Gulf of Mexico, and satellite imagery shows that this activity is intensifying and growing more organized. A center of circulation is becoming more defined about 60 miles southwest of Panama City, Florida. Strong upper-level winds out of the northeast are creating a moderate 10 - 20 knots of wind shear over ex-TD 5, and this shear is keeping heavy thunderstorms from forming on the northern side of the center of circulation. Thus, I expect that heavy thunderstorms will be slow to develop over land today. By Tuesday, ex-TD 5 should be able to intensify into a tropical depression or weak tropical storm with 40 - 45 mph winds, and heavy rains should spread across the entire Gulf Coast from central Louisiana to the Florida Panhandle. All of the models bring ex-TD 5 back ashore over Louisiana on Tuesday, and it is unlikely the storm will get sustained winds stronger than 50 mph. The GFDL model predicts ex-TD 5 will stay below tropical storm strength, while the HWRF predicts a 45-mph tropical storm at landfall on Tuesday. The Hurricane Hunters will fly into ex-TD 5 this afternoon to see if it has regenerated into a tropical depression. NHC is giving the system a 60% chance of developing into a tropical depression.


Figure 1. Morning satellite image of the remnants of TD 5.

Elsewhere in the tropics
All of the major models continue to predict a major pattern shift in the global atmospheric circulation late this week, which leads to breakdown of the Russian heat wave and start to the Cape Verdes hurricane season. Most of the models predict a tropical storm will form off the coast of Africa late this week, and track west-northwestward across the Atlantic. As usual, it is highly uncertain what track a storm that has yet to form might take.

The NOGAPS model is predicting the development of a strong tropical disturbance near the coast of Honduras late this week.

Smoke clears from Moscow
Moderate westerly winds over the past few hours have cleared Moscow's air, bringing an end to a 42-hour period where smoke from persistent wildfires blanketed the city. Temperatures at Moscow's Domodedovo airport hit 31°C (88°F) today, which is 11°C (20°F) above average. The latest forecast for Moscow calls continued very hot temperatures and light and variable winds through Wednesday, as Russia's record heat wave continues. However, on Thursday, a strong trough of low pressure is expected to move through European Russia, finally bringing an end to the Great Russian Heat Wave of 2010.


Figure 2. Departure of temperature from average for July, 2010. Image credit: National Climatic Data Center (NCDC).

Second or fifth warmest July on record for the globe
July 2010 was the second warmest July on record, behind 1998, according to the National Oceanic and Atmospheric Administration's (NOAA's) National Climatic Data Center (NCDC). July was the first month since February that was not the warmest on record. NASA's Goddard Institute for Space Studies rated July 2010 the fifth warmest July on record. Both NOAA and NASA rated the year-to-date period, January - July, as the warmest such period on record. July 2010 global ocean temperatures were the fifth warmest on record, while land temperatures were the warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 2nd warmest on record in July, according to University of Alabama Huntsville (UAH), and the warmeest on record, according to Remote Sensing Systems (RSS).

For those interested, NCDC has a page of notable weather highlights from July 2010.

Russia, Finland, and Qatar set all time heat records
Three nations--Russia, Finland, and Qatar--recorded their hottest temperatures in history during July 2010. No nation set a coldest temperature of all time record.

Finland recorded its hottest temperature on July 29, 2010, when the mercury hit 99°F (37.2°C) at Joensuu. The old (undisputed) record was 95°F (35°C) at Jyvaskyla on July 9, 1914.

Qatar had its hottest temperature in history on July 14, 2010, when the mercury hit 50.4°C (122.7°F) at Doha Airport.

Russia had its hottest temperature in history on July 11, when the mercury rose to 44.0°C (111.2°F) in Yashkul, Kalmykia Republic, in the European portion of Russia near the Kazakhstan border. The previous hottest temperature in Russia (not including the former Soviet republics) was the 43.8°C (110.8°F) reading measured at Alexander Gaj, Kalmykia Republic, on August 6, 1940. The remarkable heat in Russia this year has not been limited just to the European portion of the country--the Asian portion of Russia also recorded its hottest temperature in history this year, a 42.7°C (108.9°F) reading at Kara, in the Chita Republic on June 24. The 42.3°C (108.1°F) reading on June 25 at Belogorsk, near the Amur River border with China, also beat the old recrod for the Asian portion of Russia. The previous record for the Asian portion of Russia was 41.7°C (107.1°F) at Aksha on July 21, 2004.

All of these records are unofficial, and will need to be verified by the World Meteorological Organization (WMO.) The source for the previous all-time records listed here is the book Extreme Weather by Chris Burt.

Seventeenth warmest July on record for the U.S.
For the contiguous U.S., it was the 17th warmest July in the 116-year record, according to the National Climatic Data Center. The year-to-date period, January to July, was the 27th warmest such period on record. Two states, Delaware and Rhode Island, had their warmest July on record. Fourteen other states had a top-ten warmest July on record, including nearly every state on the Atlantic East Coast. No state recorded a top-ten coldest July.

U.S. precipitation
For the contiguous U.S., July 2010 ranked as the 36th wettest July in the 116-year record. Four states--Iowa, North Dakota, South Dakota, and Nebraska--had a top ten wettest July on record. Only Louisiana had a top-ten driest July on record.


Figure 3. The record-setting hailstone of July 23, 2010, that fell on Vivian, South Dakota. Image credit: National Weather Service, South Dakota.

Record hailstone falls in South Dakota
A severe storm on July 23rd dropped hundreds of massive hailstones on the small town of Vivian, South Dakota. Local reports stated that every house in Vivian sustained some type of hail damage. One of the stones collected broke the U.S. record not only for the largest hailstone (in diameter) but also the heaviest. The stone measured 8 inches (20.3 cm) in diameter, 18.5 inches (47.0 cm) in circumference, and weighed 1.9375 lbs (0.89 kg). It was also reported that the hailstone was originally much larger, but the freezer it was stored in lost power for about five to six hours and the person who collected it kept opening the freezer door to show friends and relatives. Even so, it smashed the previous hailstone record of 7 inches (17.8 cm) diameter, collected in southern Nebraska in June 2003. The world record for the heaviest hailstone belongs to Bangladesh, with a stone collected in April 1986 that weighed 2.25 lb (1.02 kg).

U.S. tornadoes
On July 25th, an EF-1 tornado touched down in Bronx County, New York, marking only the second ever recorded in the Bronx. On July 26th, an EF-3 tornado hit rural Sheridan County, Montana, killing two. This ties as the deadliest tornado in Montana history, and only the fourth EF-3 or stronger tornado ever observed in the state.

La Niña intensifies to moderate strength
The equatorial Eastern Pacific Ocean is now experiencing moderate La Niña conditions. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", dropped to 1.1°C below average by August 16, according to NOAA.. The Australian Bureau of Meteorology put this number at 1.0°C below average (as of August 8.) Moderate La Niña conditions are defined as occurring when this number reaches 1.0°C below average. SSTs 1.5°C below average would qualify as strong La Niña conditions. La Niña conditions must be present for several months before this will be officially classified as a La Niña event, but it is highly likely that a full-fledged La Niña event lasting at least seven more months has arrived. We started out the year with a strong El Niño, so it may seem surprising that we have transitioned La Niña so quickly, However, historically, about 35 - 40% of El Niño events are followed by a La Niña within the same year.

It is well-known that both the number and intensity of hurricanes in the Atlantic tend to increase during La Niña events. However, as I discussed in a post in June, since 1995, neutral years (when neither an El Niño or La Niña are present) have had Atlantic hurricane activity equal to La Niña years. The last time we had a strong El Niño event followed by a La Niña event in the same year, in 1998, we had a Atlantic hurricane season 40% above average in activity, with 14 named storms, 10 hurricanes, and 3 intense hurricanes. The season was relatively late-starting, with only one named storm occurring before August 20. I'm thinking this year's season may be similar, though four or more intense hurricanes are a good bet due to the record warm SSTs.

Both El Niño and La Niña events have major impacts on regional and global weather patterns. For the remainder of August, we can expect La Niña to bring cloudier and wetter than average conditions to the Caribbean, but weather patterns over North America should not see much impact. Globally, La Niña conditions tend to cause a net cooling of surface temperatures. Thus, while the past twelve month period has been the warmest globally since record keeping began in 1880, the calendar year of 2010 will probably end up just shy of being classified as the warmest year ever.

July 2010 Arctic sea ice extent 2nd lowest on record
Northern Hemisphere sea ice extent in July 2010 was the second lowest in the 31-year satellite record, according to the National Snow and Ice Data Center. Relatively cool weather occurred this July in the Arctic, compared to 2007, when the record low was set. Ice volume was at a record low for July, though, according to University of Washington Polar Ice Center. On August 16, the fabled Northwest Passage was just a day or two from melting open, and will probably be open for navigation during most of late August and all of September.

Jeff Masters

Climate Summaries Hurricane

Updated: 10:17 PM GMT on October 21, 2011

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TD 5 may redevelop over Gulf of Mexico

By: JeffMasters, 2:30 PM GMT on August 15, 2010

The remnants of Tropical Depression Five are still spinning over southwestern Georgia, and the storm is headed southwards towards the Gulf of Mexico, where redevelopment into a tropical depression could occur by Tuesday. Latest long range radar out of Mobile, Alabama shows that a band of intense thunderstorms has developed over the northern Gulf of Mexico, and satellite imagery shows that this activity continues to intensify and expand in areal coverage. Most of the heavy rain is offshore, but I expect heavy rains will spread to the Florida Panhandle late this afternoon. These heavy rains will likely spread to coastal regions of Alabama, Mississippi, and Southeast Louisiana by Monday, as the center of ex-TD 5 approaches the coast and the storm begins to wind up again. By Tuesday, the GFS and HWRF models predict that the center will move off the coast, and TD 5 will be reborn again. The system may have enough time over water to become a weak tropical storm before making landfall Tuesday night or Wednesday morning over Southeast Louisiana. Wind shear is currently low, 5 - 10 knots, and is expected to remain low to moderate, 5 - 15 knots, over the next three days, favoring re-development of TD 5. NHC is giving a 20% chance that TD 5 will regenerate into a tropical depression by 8am EDT Tuesday. I think the odds are higher than this, perhaps 40%.


Figure 1. Morning satellite image of the remnants of TD 5.

Elsewhere in the tropics
All of the major models have been predicting a major pattern shift in the global atmosphere late this week, which leads to breakdown of the Russian heat wave and the start of the Cape Verdes hurricane season. The models have been consistently predicting a tropical storm will form off the coast of Africa late this week, and track west-northwestward across the Atlantic. As usual, it is highly uncertain what track a storm that has yet to form might take.

The NOGAPS model is predicting possible development of a tropical depression near the coast of Nicaragua or Honduras late this week.

Smoke envelops Moscow again
The favorable northerly winds that had blown in cooler air and kept smoke away from Moscow slackened today, as high pressure built in. The return of the high pressure ridge that has brought European Russia its worst heat wave in history means several more days of light and variable winds that will keep wildfire smoke over or near Moscow. Very hot weather at least 10°C (18°F) above average will also be rule, and temperatures at Moscow's Domodedovo airport hit 31°C (88°F) today. This is 11°C (20°F) above average. The latest forecast for Moscow calls for high temperatures near 30°C for the next five days. Long range forecasts from the ECMWF and GFS models continue to suggest that a series of troughs of low pressure will attack the ridge of high pressure anchored over Russia late this week, bringing an end to the Great Russian Heat Wave of 2010 by early next week.


Figure 2. Image from Friday by NASA's Aqua satellite showing smoke from wildfires burning to the southeast of Moscow. Northerly winds were keeping the smoke from blowing over the city. Image credit: NASA.

Donations urgently needed in Pakistan
The devastation wrought by the worst flooding in Pakistan's history requires a huge response by the international community. Wunderblogger Dr. Ricky Rood, author of our Climate Change Blog, has a friend working in Pakistan who underscored the desperate situation there:

This is the worst natural disaster in the history of Pakistan in terms of number of people and area affected. Although not as many people have been killed as in the 2005 earthquake, we have already nearly 900,000 displaced persons thus far just in Khyber Pakhtunkhwa. Crops are destroyed; shops, hotels, and other business have simply been swept away in Swat, which had just this year been cleared of Taliban and was on the way to recovery; and districts closer to Peshawar and parts of Peshawar district are still, or perhaps again after yesterday/today, under water. After the immediate emergency response, it will be years of rebuilding to replace what has been lost and to start to develop again. I know you have the power to control the weather, so if you cold give us a week or two without more rain at least we could keep the helicopters flying and give people a chance to go to their homes, recover what might still be there, set up tents if we can get enough to them, and start to clean up."

She gave the following recommendations for charities that do work in the flood-ravaged zone, and are effective at getting aid to those who need it the most:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

She mentioned that it is better to send money to the organizations doing the relief work than to try to organize shipments of goods.

Next update
I'll have an update Monday morning.

Jeff Masters

Hurricane

Updated: 8:16 PM GMT on January 03, 2012

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Causes of the Russian heat wave and Pakistani floods

By: JeffMasters, 2:56 PM GMT on August 13, 2010

The Great Russian Heat Wave of 2010 is one of the most intense, widespread, and long-lasting heat waves in world history. Only the European heat wave of 2003, which killed 35,000 - 50,000 people, and the incredible North American heat wave of July 1936, which set all-time extreme highest temperature records in fifteen U.S. states, can compare. All of these heat waves were caused by a highly unusual kink in the jet stream that remained locked in place for over a month. The jet stream is an upper-level river of air, between the altitudes of about 30,000 - 40,000 feet (10,000 - 12,000 meters). In July over Europe and Asia, the jet stream has two branches: a strong southern "subtropical" jet that blows across southern Europe, and a weaker "polar" jet that blows across northern Europe. The polar jet stream carries along the extratropical cyclones (lows) that bring the mid-latitudes most of their precipitation. The polar jet stream also acts as the boundary between cold, Arctic air, and warm tropical air. If the polar jet stream shifts to the north of its usual location, areas just to its south will be much hotter and drier than normal. In July 2010, a remarkably strong polar jet stream developed over northern Europe. This jet curved far to the north of Moscow, then plunged southwards towards Pakistan. This allowed hot air to surge northwards over most of European Russia, and prevented rain-bearing low pressure systems from traveling over the region. These rain-bearing low pressure systems passed far to the north of European Russia, then dove unusually far to the south, into northern Pakistan. The heavy rains from these lows combined with Pakistan's usual summer monsoon rains to trigger Pakistan's most devastating floods in history.


Figure 1. Winds of the jet stream at an altitude of 300 millibars (roughly 30,000 feet high). Left: Average July winds from the period 1968 - 1996 show that a two-branch jet stream typically occurs over Europe and Asia--a northern "polar" jet stream, and a more southerly "subtropical" jet stream. Right: the jet stream pattern in July 2010 was highly unusual, with a very strong polar jet looping far to the north of Russia, then diving southwards towards Pakistan. Image credit: NOAA/ESRL.

What caused this unusual jet stream pattern?
The unusual jet stream pattern that led to the 2010 Russian heat wave and Pakistani floods began during the last week of June, and remained locked in place all of July and for the first half of August. Long-lived "blocking" episodes like this are usually caused by unusual sea surface temperature patterns, according to recent research done using climate models. For example, Feudale and Shukla (2010) found that during the summer of 2003, exceptionally high sea surface temperatures of 4°C (7°F) above average over the Mediterranean Sea, combined with unusually warm SSTs in the northern portion of the North Atlantic Ocean near the Arctic, combined to shift the jet stream to the north over Western Europe and create the heat wave of 2003. I expect that the current SST pattern over the ocean regions surrounding Europe played a key role in shifting the jet stream to create the heat wave of 2010. Note that the SST anomaly pattern is quite different this year compared to 2003, which may be why this year's heat wave hit Eastern Europe, and the 2003 heat wave hit Western Europe. Human-caused climate change also may have played a role; using climate models, Stott et al. (2004) found it very likely (>90% chance) that human-caused climate change has at least doubled the risk of severe heat waves like the great 2003 European heat wave.


Figure 2. A comparison of the departure of sea surface temperature (SST) from average just prior the the start of the great European heat waves of 2003 and 2010. Temperatures in the Mediterranean Sea were up to 4°C above average in 2003, which has been implicated as a major cause of the Western European heat wave of 2003. Image credit: NOAA/NESDIS.

References
Feudale, L., and J. Shukla (2010), "Influence of sea surface temperature on the European heat wave of 2003 summer. Part I: an observational study", Climate Dynamics DOI: 10.1007/s00382-010-0788-0

Stott, P.A., Stone, D.A., and M.R. Allen (2004), "Human contribution to the European heatwave of 2003", Nature 432, 610-614 (2 December 2004) | doi:10.1038/nature03089. (Here is a free version of the paper, presented at a conference.)

The World Meteorological Organization (WMO) has posted an analysis of the recent extreme weather events, concluding, "the sequence of current events matches IPCC projections of more frequent and more intense extreme weather events due to global warming."

See also my posts, The Great Russian Heat Wave of 2010: 102°F in Moscow and, Over 15,000 likely dead in Russian heat wave; Asian monsoon floods kill hundreds more.

Moscow sees real relief from the Great Russian Heat Wave of 2010
For the first time in more than a month, temperatures at Moscow's Domodedovo airport failed to exceed 30°C (86°F) today. Clouds and thunderstorms blew into the city this morning, keeping the high temperature down to just 29°C (84°F). This breaks a string of 35 straight days when the temperature reached 30°C. At Moscow's official observing site, the Moscow Observatory, this string was 30 days. Moscow's average high temperature for August 13 is 20°C (68°F), so today's temperatures were still well above normal. However, today's cool-down marks the beginning of the end for Russia's great heat wave. The latest forecast for Moscow calls for high temperatures below 30°C for the coming week, and Moscow may not exceed that threshold for the remainder of summer. Long range forecasts from the ECMWF and GFS models continue to suggest that a series of troughs of low pressure will attack the ridge of high pressure anchored over Russia, bringing cooler temperatures just 5°C (8°F) above average to Russia late next week. By ten days from now, the ECMWF model shows a strong trough of low pressure over Moscow, and a end to the Great Russian Heat Wave of 2010. Moscow still has to concern itself with smoke from the wildfires burning southeast of the city; winds are expected to shift early next week and bring the smoke towards the city again. However, the cooler weather should aid fire-fighting efforts, so the smoke problems should not be as bad as last week's nightmare.


Figure 2. Image from NASA's Aqua satellite of smoke from wildfires burning to the southeast of Moscow yesterday, August 12, 2010. Northerly winds were keeping the smoke from blowing over the city. Image credit: NASA.

The tropics are quiet
The remnants of Tropical Depression Five continue to bring heavy rain to portions of Southeast Louisiana today. Up to five inches of rain has fallen in regions near New Orleans. The GFS model predicts that the remains of TD 5 could move off the coast of Mississippi by the middle of next week and regenerate, but none of the other models is making this forecast. Both the GFS and ECMWF models are predicting that a tropical storm will develop off the coast of Africa by next Friday, August 20.

Donations urgently needed in Pakistan
The devastation wrought by the worst flooding in Pakistan's history requires a huge response by the international community. Wunderblogger Dr. Ricky Rood, author of our Climate Change Blog, has a friend working in Pakistan who underscored the desperate situation there:

This is the worst natural disaster in the history of Pakistan in terms of number of people and area affected. Although not as many people have been killed as in the 2005 earthquake, we have already nearly 900,000 displaced persons thus far just in Khyber Pakhtunkhwa. Crops are destroyed; shops, hotels, and other business have simply been swept away in Swat, which had just this year been cleared of Taliban and was on the way to recovery; and districts closer to Peshawar and parts of Peshawar district are still, or perhaps again after yesterday/today, under water. After the immediate emergency response, it will be years of rebuilding to replace what has been lost and to start to develop again. I know you have the power to control the weather, so if you cold give us a week or two without more rain at least we could keep the helicopters flying and give people a chance to go to their homes, recover what might still be there, set up tents if we can get enough to them, and start to clean up."

She gave the following recommendations for charities that do work in the flood-ravaged zone, and are effective at getting aid to those who need it the most:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

She mentioned that it is better to send money to the organizations doing the relief work than to try to organize shipments of goods.

Jeff Masters

Climate Change Heat

Updated: 11:30 PM GMT on April 21, 2011

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A record quiet start to the 2010 Northern Hemisphere tropical cyclone season

By: JeffMasters, 3:42 PM GMT on August 12, 2010

The remnants of Tropical Depression Five have re-organized this morning, and the storm is pounding Southeast Louisiana with heavy rains. Radar imagery out of New Orleans shows that the remains of TD 5 have have formed some respectable low-level spiral bands that have brought heavy rains in excess of five inches in some areas. However, with the circulation center now moving over land, not much further development can occur.


Figure 1. Morning radar image of TD Five's remains.

Why so quiet in the Atlantic?
The Tropical Atlantic is quiet, and there are no threat areas to discuss today. The Invest 93 system we were tracking has been destroyed by dry air and wind shear. There are a couple of long-range threats suggested by some of the models--the GFS model predicts a tropical depression could form off the coast of Mississippi six days from now, and the NOGAPS model thinks something could get going in the Gulf of Mexico's Bay of Campeche seven days from now. Neither of these possibilities are worthy of concern at present. Overall, it's been a surprisingly quiet August, considering the pre-season predictions of a hyperactive season. According the National Hurricane Center, this hurricane season has been exactly average so far. There have been three named storms and one hurricane as of August 12. The average date of formation of the third named storm is August 13. One hurricane typically forms by August 10. One reason for this year's inactivity may be an unusual number of upper-level low pressure systems that have paraded across the tropical Atlantic. These lows, also called Tropical Upper Tropospheric Trough (TUTT) lows, tend to bring high wind shear that inhibits tropical cyclone formation. The other major factor appears to be that vertical instability has been unusually low in the Atlantic over the past month. Instability is measured as the difference in temperature between the surface and the top of the troposphere (the highest altitude that thunderstorm tops can penetrate to.) If the surface is very warm and the top of the troposphere is cold, an unstable atmosphere results, which helps to enhance thunderstorm updrafts and promote hurricane development. Since SSTs in the Atlantic are at record highs, enhancing instability, something else must be going on. Dry air can act to reduce instability, and it appears that an unusually dry atmosphere over the Atlantic this month is responsible for the lack of instability.


Figure 2. Vertical instability (in °C) over the Caribbean (left) and tropical Atlantic between the Lesser Antilles Islands and coast of Africa (right) in 2010. Normal instability is the black line, and this year's instability levels are in blue. The atmosphere became much more stable than normal in both regions at the end of July. This lack of instability also extends to the Gulf of Mexico and North Atlantic Ocean between Europe and North America, as well as the Western Pacific east of the Philippines, and the South Indian Ocean. Image credit: NOAA/CIRA.

A record quiet start to the 2010 tropical cyclone season in the Northern Hemisphere
What is really odd about this year, though, is the lack of tropical cyclone activity across the entire Northern Hemisphere. Usually, if one ocean basin is experiencing a quiet season, one of the other ocean basins is going bonkers. That is not the case this year. Over in the Eastern Pacific, there have been five named storms and two hurricanes. The average is seven named storms and four hurricanes for this point in the season. This year's quiet season is not too surprising, since there is a moderate La Niña event underway, and La Niña conditions usually supresses Eastern Pacific hurricane activity. But over in the Western Pacific, which usually generates more tropical cyclones than any ocean basin on Earth, it has been a near-record quiet season. Just four named storms have occurred in the West Pacific this year, and the average for this date is eleven. Only one typhoon season has had fewer named storms this late in the season--1998, with just three. The total number of named storms in the Northern Hemisphere thus far this year is fifteen, which is the fewest since reliable records began in 1948. Second place belongs to 1983 and 1957, with eighteen named storms. According to an email I received from NOAA hurricane researcher Gabe Vecchi, the lack of tropical cyclones so far this year in the Northern Hemisphere is between a 1-in-80 and 1-in-100 year event.

So, what is causing this quiet tropical cyclone season? One possibility is that since Northern Hemisphere land areas have heated up to record temperatures this summer, this has created strong rising motion over the continents. This rising motion must be compensated by strong sinking motion over the adjacent oceans in order to conserve mass. Sinking air causes drying and an increase in stability. Another possibility is that the unusual jet stream configuration that is responsible for the Russia heat wave and record flooding in Pakistan is also bringing dry, stable air to the Northern Hemisphere's tropical cyclone breeding grounds. It is also possible that climate change is causing the reduction in tropical cyclone activity, for a variety of complex reasons. Computer simulations of a future warmer climate generally show a reduction in global number of tropical cyclones (though the strongest storms get stronger), and it is possible we are seeing a preview of that future climate. Or, this year's quietness may simply be natural variability. It will be interesting to see when the Russian heat wave breaks if vertical instability over the Atlantic increases back to normal levels. Current forecasts from the GFS and ECMWF models project the Russian heat wave to break late next week.

Moscow's air remains clear; coolest temperatures in two weeks
Moscow's winds remained favorable for keeping smoke away from the city today, and temperatures "cooled" to at Moscow's Domodedovo airport to 33°C (91°F)--the lowest maximum temperature since a high of 32°C (90°F) was recorded on July 30. Moscow's airport has reached a maximum temperature of 30°C (86°F) or higher for 35 consecutive days now (at Moscow's official observing site, the Moscow Observatory, this string is 30 days.) Moscow's average high temperature for August 12 is 20°C (68°F). Moscow's high temperatures have averaged 15°C (27°F) above average so far this August--a truly extraordinary anomaly for a country so famous for its notorious cold weather. The latest forecast for Moscow calls for high temperatures of 30 - 33°C (86 - 91°F) Thursday through Monday. This is still 23°F above normal, but will be a welcome change from the extreme heat of the past two weeks. Long range forecasts from the ECMWF and GFS models continue to suggest that a series of troughs of low pressure will begin to attack the ridge of high pressure anchored over Russia beginning on Wednesday, bringing cooler temperatures just 5°C (8°F) above average to Russia late next week. By ten days from now, the ECMWF model shows a strong trough of low pressure over Moscow, and a end to the Great Russian Heat Wave of 2010.

Next update
I'll have an update Friday morning.

Jeff Masters

Hurricane

Updated: 3:47 PM GMT on August 12, 2010

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Tropical Depression Five struggling

By: JeffMasters, 8:13 PM GMT on August 11, 2010

Tropical Depression Five is in serious decline, thanks to an unexpected increase of wind shear to about 20 knots this afternoon. Long range radar out of the Florida Panhandle shows a fair amount of heavy thunderstorm activity, but little organization into low-level rain bands. TD 5 has brought up to two inches of rain to the New Orleans region. The Hurricane Hunters have just left TD 5, and they found no well-defined surface circulation, a pressure that had risen since this morning's flight, and top winds of just 30 mph. It is questionable whether TD 5 really was a tropical depression for much of the day. Recent satellite images suggest that the center of the storm has relocated near some of the heavier thunderstorms, about 60 miles southeast of the Alabama/Mississippi border. If this new center does indeed become stable, TD 5 will move ashore in the warning area tonight or early Thursday morning, before the depression can develop into a tropical storm. TD 5 is still capable of dropping heavy rains of 3 - 5 inches along its path, however, since the storm is expected to slow down after landfall.


Figure 1. Afternoon radar image of TD Five from the Florida Panhandle radar.

93L
The tropical wave (Invest 93) in the middle Atlantic Ocean that has been close to tropical depression status for three days has suffered a setback today, as dry air driven into the core of the storm by strong upper-level winds disrupted the circulation. The disturbance still has a well-defined surface circulation, but only a very limited amount of heavy thunderstorm activity. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next three days, which is low enough that 93L could become a tropical depression at any time during that period. NHC is giving 93L a 50% chance of developing into a tropical depression by Friday afternoon. A strong trough of low pressure moving across the central Atlantic is recurving 93L to the north, and the system should only be a concern to shipping interests.

Moscow's air clears, but it is still extraordinarily hot
A thunderstorm blew through Moscow early this morning, bringing a little rain and a very welcome shift of wind direction. The wind shift freed the city from the persistent wild fire smoke that had plagued the city for seven straight days. Temperatures at Moscow's Domodedovo airport hit 35°C (95°F) today, the 29th day in row that temperatures have exceeded 30°C (86°F) in Moscow. The average high temperature for August 11 is 21°C (69°F). Moscow's high temperatures have averaged 15°C (27°F) above average for the first eleven days of August--a truly extraordinary anomaly. There is some modest relief in sight--the latest forecast for Moscow calls for high temperatures of 30 - 31° (86 - 88°F) Thursday through Sunday. This is still 20°F above normal, but will be a welcome change from the extreme heat of the past two weeks. Long range forecasts from the ECMWF and GFS models show no major change to the ridge of high pressure locked in over Russia, for at least the next seven days. However, both models suggest that a trough of low pressure may be able to erode the ridge significantly 8 - 10 days from now, bringing cooler temperatures of 5°C (8°F) above average.

Next update
I'll have an update Thursday morning.

Jeff Masters

Hurricane

Updated: 8:16 PM GMT on January 03, 2012

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Tropical Depression Five a heavy rain threat; the smoke clears in Moscow

By: JeffMasters, 3:23 PM GMT on August 11, 2010

Tropical Depression Five is currently weak and disorganized, but it has the potential to organize into a potent rain-maker that may bring extremely heavy rains to Louisiana, Mississippi, Alabama, and Georgia over the next four days. Outer rain bands from TD 5 are already affecting the New Orleans region, where as much as two inches of rain has fallen in isolated regions. TD 5 has only limited heavy thunderstorm activity at present, thanks to an infusion of dry air early this morning from an upper-level low pressure system over the Gulf of Mexico. However, TD 5 is steadily recovering from this blow, and water vapor imagery shows the atmosphere is moistening in the eastern Gulf of Mexico as TD 5 builds more heavy thunderstorms. Wind shear is currently a moderate 10 - 15 knots over TD 5, and water temperatures are very warm, 31°C. The Hurricane Hunters have left TD 5, and a new aircraft is scheduled to arrive this afternoon.


Figure 1. Morning radar image of TD Five from the New Orleans radar.

Forecast for TD 5
The latest SHIPS model forecast predicts that wind shear will drop to the low range, 5 - 10 knots, by tonight, and remain low for the remainder of TD 5's life. The main hindrance to development will be the current large, disorganized nature of the storm's circulation. Without a tight, well-defined center of circulation, it will take time for the storm to intensify, and I don't expect TD 5 will have time to become more than a 50 mph tropical storm. NHC is giving TD 5 just a 2% chance of reaching hurricane strength. The main threat from TD 5 will be rainfall. This is a slow-moving storm, and the steering currents pushing the storm towards the coast are expected to weaken Thursday and Friday. TD 5 will likely slow to a crawl on Thursday and Friday, moving at just 3 - 5 mph. This will allow the storm to dump very heavy rains in excess of eight inches in isolated regions.

93L
There is not much new to report on the tropical wave (Invest 93) in the middle Atlantic Ocean that has been close to tropical depression status for three days now. The disturbance has a well-defined surface circulation, but only a limited amount of heavy thunderstorm activity, thanks to dry air aloft and wind shear of 10 - 20 knots. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next three days, which is low enough that 93L could become a tropical depression at any time during that period. NHC is giving 93L a 70% chance of developing into a tropical depression by Friday morning. The GFS, GFDL, and HWRF models predict 93L will develop, and the GFDL forecasts that the storm will become a hurricane. A strong trough of low pressure moving across the central Atlantic is recurving 93L to the north, and the system should only be a concern to shipping interests. None of the reliable computer models are forecasting tropical cyclone development in the Atlantic over the next seven days, other than for 93L.

Moscow's air clears, but it is still extraordinarily hot
A thunderstorm blew through Moscow early this morning, bringing a little rain and a very welcome shift of wind direction. The wind shift freed the city from the persistent wild fire smoke that had plagued the city for seven straight days. Temperatures at Moscow's Domodedovo airport hit 35°C (95°F) today, the 29th day in row that temperatures have exceeded 30°C (86°F) in Moscow. The average high temperature for August 11 is 21°C (69°F). Moscow's high temperatures have averaged 15°C (27°F) above average for the first eleven days of August--a truly extraordinary anomaly. There is some modest relief in sight--the latest forecast for Moscow calls for high temperatures of 30 - 31° (86 - 88°F) Thursday through Sunday. This is still 20°F above normal, but will be a welcome change from the extreme heat of the past two weeks. Long range forecasts from the ECMWF and GFS models show no major change to the ridge of high pressure locked in over Russia, for at least the next seven days. However, both models suggest that a trough of low pressure may be able to erode the ridge significantly 8 - 10 days from now, bringing cooler temperatures of 5°C (8°F) above average.

Next update
I'll have an update this afternoon between 3 - 4 pm EDT.

Jeff Masters

Hurricane

Updated: 8:17 PM GMT on January 03, 2012

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Pakistan's Katrina; 94L could develop in Gulf of Mexico

By: JeffMasters, 3:23 PM GMT on August 10, 2010

The monsoon season of 2010 continues to generate havoc in Asia, as lingering rains from the latest monsoon low continue to affect hard-hit Pakistan, China, and India. At least 702 are now reported dead and 1,042 are missing in China's Gansu province, due to torrential monsoon rains that triggered a deadly landslide and extreme flooding on Sunday. At least 137 died in floods and landslides in the neighboring Indian state of Kashmir over the weekend, with 500 people missing. Monsoon flooding and landslides have also killed at least 65 people in Afghanistan in the past two weeks. But no country has suffered more than Pakistan, where monsoon floods have destroyed huge portions of the nation's infrastructure and killed at least 1600 people. The number of people affected or needing assistance has been estimated to be as high as 13 million people--8% of the nation's population. The disaster is the worst natural disaster in Pakistan's history, and is rightfully being called "Pakistan's Katrina."


Figure 1. The heavy thunderstorms of a monsoon depression lie over northwestern Pakistan near Islamabad in this visible satellite image taken by NASA's MODIS instrument on July 29, 2010. Image credit: NASA.

Monsoons: a primer
In summer, the sun warms up land areas more strongly than ocean areas. This occurs because wind and ocean turbulence mix the ocean's absorbed heat into a "mixed layer" approximately 50 meters deep, whereas on land, the sun's heat penetrates at a slow rate to a limited depth. Furthermore, due to its molecular properties, water has the ability to absorb more heat than the solid materials that make up land. As a result of this summertime differential heating of land and ocean, a low pressure region featuring rising air develops over land areas. Moisture-laden ocean winds blow towards the low pressure region and are drawn upwards once over land. The rising air expands and cools, condensing its moisture into some of the heaviest rains on Earth--the monsoon. Monsoons operate via the same principle as the familiar summer afternoon sea breeze, but on a grand scale. Each summer, monsoons affect every continent on Earth except Antarctica, and are responsible for life-giving rains that sustain the lives of billions of people. In India, home for over 1.1 billion people, the monsoon provides 80% of the annual rainfall. However, monsoons have their dark side as well--hundreds of people in India and surrounding nations die in an average year in floods and landslides triggered by heavy monsoon rains. The most deadly flooding events usually come from monsoon depressions (also known as monsoon lows.) A monsoon depression is similar to (but larger than) a tropical depression. Both are spinning storms hundreds of kilometers in diameter with sustained winds of 50 - 55 kph (30 - 35 mph), nearly calm winds at their center, and generate very heavy rains. Each summer, approximately 6 - 7 monsoon depressions form over the Bay of Bengal and track westwards across India. Four monsoon depressions originated in the Bay of Bengal in the El Niño-weakened monsoon season of 2009. This year's first monsoon depression formed on July 24, crossed over India, and reached Pakistan on July 27. The rains increased in intensity over the next two days, peaking on July 29 and 30, when a low pressure system that moved across Pakistan from the west enhanced rainfall from the monsoon depression. Over the 3-day period July 28 - 30, torrential rains in excess of 8 inches (203 mm) fell in many regions of northwest Pakistan Rainfall amounts at two stations in the catchment basins of the Jhelum River and Indus River reached 19.49" (495 mm) for the month of July, and 7.56" (192 mm) fell in a single day, July 30, at Tarbela. A second monsoon depression arrived in Pakistan on August 3, and has brought additional heavy rains.

Are the this year's monsoon floods due to global warming?
No single weather event can be attributed to climate change, but a warming climate does load the dice in favor of heavier extreme precipitation events. This occurs because more water vapor can evaporate into a warmer atmosphere, increasing the chances of record heavy downpours. In a study published in Science in 2006, Goswami et al. found that the level of heavy rainfall activity in the monsoon over India had more than doubled in the 50 years since the 1950s, leading to an increased disaster potential from heavy flooding. Moderate and weak rain events decreased over the past 50 years, leaving the total amount of rain deposited by the monsoon roughly constant. The authors commented, "These findings are in tune with model projections and some observations that indicate an increase in heavy rain events and a decrease in weak events under global warming scenarios." We should expect to see an increased number of disastrous monsoon floods in coming decades if the climate continues to warm as expected. Since the population continues to increase at a rapid rate in the region, death tolls from monsoon flooding disasters are likely to climb dramatically in coming decades.

References
Goswami, et al., 2006, " Increasing Trend of Extreme Rain Events Over India in a Warming Environment", Science, 1 December 2006:Vol. 314. no. 5804, pp. 1442 - 1445 DOI: 10.1126/science.1132027

Dave's Landslide blog has some great discussions of the flooding and destruction wrought by the terrible monsoon rains this year in Pakistan, India, Afghanistan, and China.

Donations urgently needed
The massive humanitarian crisis in Pakistan requires a huge response by the international community. Wunderblogger Dr. Ricky Rood, author of our Climate Change Blog, has a friend working in Pakistan who underscored the desperate situation there:

This is the worst natural disaster in the history of Pakistan in terms of number of people and area affected. Although not as many people have been killed as in the 2005 earthquake, we have already nearly 900,000 displaced persons thus far just in Khyber Pakhtunkhwa. Crops are destroyed; shops, hotels, and other business have simply been swept away in Swat, which had just this year been cleared of Taliban and was on the way to recovery; and districts closer to Peshawar and parts of Peshawar district are still, or perhaps again after yesterday/today, under water. After the immediate emergency response, it will be years of rebuilding to replace what has been lost and to start to develop again. I know you have the power to control the weather, so if you cold give us a week or two without more rain at least we could keep the helicopters flying and give people a chance to go to their homes, recover what might still be there, set up tents if we can get enough to them, and start to clean up."

She gave the following recommendations for charities that do work in the flood-ravaged zone, and are effective at getting aid to those who need it the most:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

She mentioned that it is better to send money to the organizations doing the relief work than to try to organize shipments of goods.


Figure 2. Morning radar image of 94L from the Key West radar.

94L
A 1010 mb low pressure system (94L) near the Florida Keys is generating disorganized heavy thunderstorms over Florida and the adjacent waters, and could become a tropical or subtropical depression as early as Wednesday. Current Key West radar shows the rotation of the storm, but the thunderstorm activity has not yet organized into low-level spiral bands. A few areas in the Keys and extreme South Florida have seen 1 - 2 inches of rain thus far from 94L. Wind shear is currently a moderate 10 - 20 knots over 94L, and water temperatures are very warm, 30 - 31°C. Water vapor satellite imagery shows that 94L is forming beneath an upper-level low with plenty of dry air, and there is a substantial flow of dry, continental air wrapping into 94L. This dry air is retarding the development of 94L, and may force the storm to organize into a subtropical storm instead of a tropical storm. A subtropical storm typically has a large, cloud free center of circulation, with very heavy thunderstorm activity in a band removed at least 100 miles from the center. The difference between a subtropical storm and a tropical storm is not that important as far as the winds they can generate, but tropical storms generate more rain. There is no such thing as a subtropical hurricane. If a subtropical storm intensifies enough to have hurricane force winds, than it must have become fully tropical. It usually takes at least two days for a subtropical storm to make the transition to a tropical storm.

Forecast for 94L
The latest SHIPS model forecast predicts that wind shear will stay in the moderate range, 10 - 20 knots, over the Gulf of Mexico this week. The storm's main problem will be dry air, and I don't expect 94L to undergo rapid development. Most of the models bring 94L ashore over Louisiana by Thursday, though the GFDL model predicts 94L could stall off the coast and not make landfall until Friday. If 94L does make landfall Thursday, it is unlikely to be a hurricane, due to all the dry air aloft in the Gulf. However, the GFDL model is predicting that the 1-day delay in landfall to Friday will allow 94L enough time to grow fully tropical and intensify into a Category 1 hurricane. I think this solution is unlikely. Storms that get their start underneath a cold, dry, upper-level low very rarely attain hurricane strength in three days. A 40 - 50 mph tropical or subtropical storm at landfall Thursday or Friday is a much more reasonable forecast.

93L
A tropical wave (Invest 93) in the middle Atlantic Ocean is close to tropical depression status. The disturbance has a well-defined surface circulation, but only a limited amount of heavy thunderstorm activity, thanks to dry air and wind shear of 10 - 20 knots affecting it due to a large upper-level low pressure system to the west. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next four days, which is low enough that 93L could become a tropical depression at any time during that period. NHC is giving 93L a 60% chance of developing into a tropical depression by Thursday morning. The GFS, GFDL, and HWRF models predict 93L will develop, and the GFDL forecasts that the storm will become a hurricane. A strong trough of low pressure moving across the central Atlantic is recurving 93L to the north, and the system should only be a concern to shipping interests. None of the reliable computer models are forecasting tropical cyclone development in the Atlantic over the next seven days, other than for 93L and 94L.

Moscow hits 99°F again today
Temperatures at Moscow's Domodedovo airport hit 37°C (99°F) today, the 28th day in row that temperatures have exceeded 30°C (86°F) in Moscow. The average high temperature for August 10 is 21°C (69°F). Moscow's high temperature have averaged 15°C (27°F) above average for the first ten days of August--a truly extraordinary anomaly. Smog and smoke from wildfires continued to blanket the city today, with the Russian Meteorological Agency reporting that pollution due to carbon monoxide, nitrogen dioxide, ozone, and hydrocarbons exceeding the safe limit by factors of 1.2 - 2.2. Air pollution levels peaked at 6.5 times the safe level on Saturday. As I reported in yesterday's post, the heat wave has likely killed at least 15,000 people in Russia so far. There is some slight relief in sight--the latest forecast for Moscow calls for high temperatures of 31 - 33°C (88 - 91°F) Wednesday though Sunday--still 20°F above normal, but better than the 27°F above normal so far this month.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Invest 94 and 93
2) A look ahead at the coming two weeks
3) Status of La Niña

Today's show will be about 30 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

Flood

Updated: 9:59 PM GMT on August 16, 2011

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Over 15,000 likely dead in Russian heat wave; Asian monsoon floods kill hundreds more

By: JeffMasters, 3:13 PM GMT on August 09, 2010

The Great Russian Heat Wave of 2010 brought temperatures of 37°C (99°F) to Moscow today, and smog and smoke from wildfires blanketed the city for a sixth straight day. Air pollution levels were 2 - 3 times the maximum safe level today, and peaked on Saturday, when when carbon monoxide hit 6.5 times the safe level. The death toll from heat and air pollution increased to approximately 330 people per day in Moscow in recent days, according to the head of the Moscow health department. Yevgenia Smirnova, an official from the Moscow registry office, said excess deaths in Moscow in July averaged 155 per day, compared to 2009. The heat wave began on June 27. These grim statistics suggest that in Moscow alone, the Great Russian Heat Wave of 2010 has likely killed at least 7,000 people so far. A plot of the departure of July 2010 temperatures from average (Figure 1) shows that the area of Russia experiencing incredible heat is vast, and that regions southeast of Moscow have the hottest, relative to average. Moscow is the largest city in Russia, with a population just over ten million, but there are several other major cities in the heat wave region. These include Saint Petersburg, Russia's 2nd most populous city (4.6 million), and Nizhny Novgorod, Russia's 5th most populous city (1.3 million people.) Thus, the Russian population affected by extreme heat is at least double the population of Moscow, and the death toll in Russia from the 2010 heat wave is probably at least 15,000, and may be much higher. The only comparable heat wave in European history occurred in 2003, and killed an estimated 40,000 - 50,000 people, mostly in France and Italy. While the temperatures in that heat wave were not as extreme as the Russian heat wave, the nighttime low temperatures in the 2003 heat wave were considerably higher. This tends to add to heat stress and causes a higher death toll. I expect that by the time the Great Russian Heat Wave of 2010 is over, it may rival the 2003 European heat wave as the deadliest heat wave in world history.


Figure 1. A comparison of August temperatures, the peak of the great European heat wave of 2003 (left) with July temperatures from the Great Russian Heat Wave of 2010 (right) reveals that this year's heat wave is more intense and covers a wider area of Europe. Image credit: NOAA/ESRL.

Worst Russian heat wave in 1,000 years of history
The temperature at Moscow's Domodedovo Airport hit 99°F (37°C) today. Prior to this year, the hottest temperature in Moscow's history was 37.2°C (99°F), set in August 1920. The Moscow Observatory has now matched or exceeded this 1920 all-time record five times in the past two weeks. Temperatures the past 27 days in a row have exceeded 30°C in Moscow. Alexander Frolov, head of Russia's weather service, said in a statement today, "Our ancestors haven't observed or registered a heat like that within 1,000 years. This phenomenon is absolutely unique." There is some slight relief in sight--the latest forecast for Moscow calls for high temperatures of 31 - 33°C (88 - 91 °F) Wednesday though Sunday.

Belarus records its hottest temperature in history for the second day in a row
The Russian heat wave has also affected the neighboring nations of Ukraine and Belarus. All three nations have recorded their hottest temperatures in history over the past few weeks. Belarus, on the western border of Russia, recorded its hottest temperature in history on Saturday, August 7, when the mercury hit 38.9°C (102°F) in Gomel. This broke the all-time record for extreme heat set just one day before, the 38.7°C (101.7°F) recorded in Gorky. Prior to 2010, the hottest temperature ever recorded in Belarus was the 38.0°C (100.4°F) in Vasiliyevichy on Aug. 20, 1946. As I described in detail in Saturday's post, Belarus' new all-time extreme heat record gives the year 2010 the most national extreme heat records for a single year--seventeen. These nations comprise 19% of the total land area of Earth. This is the largest area of Earth's surface to experience all-time record high temperatures in any single year in the historical record. Looking back at the past decade, which was the hottest decade in the historical record, Seventy-five countries set extreme hottest temperature records (33% of all countries.) For comparison, fifteen countries set extreme coldest temperature records over the past ten years (6% of all countries). Earth has now seen four consecutive months with its warmest temperature on record, and the first half of 2010 was the warmest such 6-month period in the planet's history. It is not a surprise that many all-time extreme heat records are being shattered when the planet as a whole is so warm. Global warming "loads the dice" to favor extreme heat events unprecedented in recorded history.

July SSTs in the tropical Atlantic set a new record
Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest July on record, according to an analysis I did of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were 1.33°C above average during July, beating the previous record of 1.19°C set in July 2005. July 2010 was the sixth straight record warm month in the tropical Atlantic, and had the third warmest anomaly of any month in history. The five warmest months in history for the tropical Atlantic have all occurred this year. As I explained in detail in a post on record February SSTs in the Atlantic, the Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are largely to blame for the record SSTs, though global warming and Atlantic Multidecadal Oscillation (AMO) also play a role.

The magnitude of the anomaly has increased slightly since June, because trade winds over the tropical Atlantic were at below-normal speeds during July. These lower trade wind speeds were due to the fact that the Bermuda-Azores High had below-normal surface pressures over the past month. The Bermuda-Azores High and its associated trade winds are forecast to remain at below-average strength during the next two weeks, according to the latest runs of the GFS model. This means that Atlantic SST anomalies will continue to stay at record warm levels during the remainder of August, and probably during September as well. This should significantly increase the odds of getting major hurricanes in the Atlantic during the peak part of hurricane season, mid-August through mid-October.


Figure 2. The departure of sea surface temperature (SST) from average for August 9, 2010. Image credit: NOAA/NESDIS.

94L
A area of disurbed weather (94L) over South Florida is generating disorganized heavy thunderstorms over Florida and the adjacent waters, but is not a threat to develop today due to high wind shear of 20 - 30 knots. The latest SHIPS model forecast predicts that wind shear will fall to the moderate range, 10 - 20 knots, tonight through Thursday. This relaxation in shear may allow 94L to begin to organize. However, 94L will not have much time over the Gulf of Mexico to become a tropical depression or tropical storm, as steering currents favor a westward or west-northwestward motion over the Gulf that would bring the storm ashore over the northern Gulf coast by Wednesday or Thursday. NHC is giving 94L a 20% chance of developing into a tropical depression by Wednesday morning. The Hurricane Hunters are on call to investigate 94L on Tuesday afternoon.

93L
A tropical wave (Invest 93) in the middle Atlantic Ocean is close to tropical depression status. The disturbance has a well-defined surface circulation, but only a limited amount of heavy thunderstorm activity, thanks to dry air and wind shear of 10 - 20 knots affecting it due to a large upper-level low pressure system to the west. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next two days, which should allow 93L to become a tropical depression by Tuesday. NHC is giving a 70% chance 93L will become a tropical depression by Wednesday morning. Both the GFDL and HWRF models predict 93L will develop, and the GFDL predicts the storm will become a hurricane. A strong trough of low pressure moving across the central Atlantic should force 93L to turn northward on Wednesday, and 93L should only be a concern to shipping interests. None of the reliable computer models are forecasting tropical cyclone development in the Atlantic over the next seven days, other than for 93L.

A exceptionally slow-starting typhoon season
There is one bit of good weather news to report. Over in the Western Pacific, typhoon season has been remarkably quiet this year. Prior to yesterday's formation of Tropical Storm Dianmu, just three named storms had formed this year--Tropical Storm Omais, Typhoon Conson, and Typhoon Chanthu. The average for this point in the season is ten storms. Sunday's total of three named storms in the West Pacific tied 2010 with 1998, 1954, and 1975 as the slowest starting Western Pacific typhoon season on record, for the date August 8. Now that we have Tropical Storm Dianmu in the Western Pacific, 2010 ranks as the 4th slowest start to a typhoon season as of August 9. Reliable records of typhoon activity go back to 1951.


Figure 3. Heavy downpours triggered landslides and mud-rock flows in China's Gansu Province, early Sunday morning. Image credit: www.news.cn.

The deadly 2010 monsoon kills hundreds more in China, India, and Pakistan over the weekend
The Asian Southwest Monsoon has been exceptionally deadly this year. Northwest China's Gansu province was hard hit over the weekend with torrential monsoon rains, and the resulting flooding and landslides claimed at least 127 lives. At least 1300 people are missing in the disaster. Fresh monsoon rains in Pakistan over the weekend triggered landslides that killed sixty more people, in addition to the 1,500 - 1,600 people who died in monsoon floods that began in late July. At least 137 died in floods and landslides in the neighboring Indian state of Kashmir over the weekend, with 500 people missing. Monsoon flooding and landslides have also killed at least 65 people in Afghanistan in the past two weeks. Dave's Landslide blog has some great discussions of the flooding and destruction wrought by the terrible monsoon rains this year in Pakistan, India, Afghanistan, and China. I plan to write much more about this year's deadly monsoon on Tuesday.

Next post
I'll have an update Tuesday.

Jeff Masters

Climate Change Heat Hurricane

Updated: 5:17 PM GMT on August 09, 2010

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Monsoon floods and landslides ravage China, India, and Pakistan; Colin still weak

By: JeffMasters, 1:31 PM GMT on August 08, 2010

Tropical Storm Colin continues to take its time reaching Bermuda, but should finally move past the island today as the steering currents pushing the storm northward strengthen. Colin is still suffering from wind shear and dry air being pumped in from an upper-level low pressure system to the west. Wind shear is a moderate 10 - 20 knots over Colin today, but the storm is so disorganized that it is unlikely to increase in strength more than about 10 mph before blowing past Bermuda tonight. Recent satellite imagery shows that Colin is a disorganized system, with the level-level center exposed to view and displaced to the north of the storm's heavy thunderstorm activity. The intensity and areal coverage of Colin's thunderstorms have shown a modest increase in the past few hours. Rains from these thunderstorms can be seen approaching Bermuda on Bermuda radar.

Forecast for Colin
The latest SHIPS model forecast predicts that wind shear will rise to the high range, 20 - 50 knots, tonight through Tuesday, and it is unlikely that the storm will ever attain hurricane status. Colin may bring 40 mph winds to the southeast corner of Newfoundland on Tuesday night and Wednesday.


Figure 1. Morning radar image of Colin from the Bermuda radar.

93L
A tropical wave (Invest 93) midway between the Lesser Antilles and Africa is moving west-northwest at 10 mph. This wave has plenty of spin, but only a limited amount of heavy thunderstorm activity, thanks to dry air and wind shear of 10 - 20 knots affecting it due to a large upper-level low pressure system to the west. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next four days, which may allow 93L to become a tropical storm. NHC is giving a 60% chance 93L will become a tropical depression by Tuesday morning. Both the GFDL and HWRF models predict 93L will develop, and the GFDL predicts the storm will become a hurricane. This storm will probably recurve out to sea, and only be a concern to shipping interests. There are no other areas of concern the models are showing for the next seven days.


Figure 2. Monsoon floods in Pakistan destroyed this section of the Karakoram Highway last week. Image credit: Pamir Times.

The deadly 2010 monsoon kills hundreds in China and India over the weekend
The Asian Southwest Monsoon has hit yet another nation with extreme rains and deadly flooding. Northwest China's Gansu province was hard hit with torrential monsoon rains yesterday, and the resulting flooding and landslides claimed at least 127 lives. Over the past two weeks, at least 1,600 people have perished in Pakistan's monsoon floods, which some have called Pakistan's Katrina. At least 137 died in floods and landslides in the neighboring Indian state of Kashmir over the weekend, and monsoon flooding and landslides have also killed at least 65 people in Afghanistan in the past two weeks. Dave's Landslide blog has some great discussions of the flooding and destruction wrought by the terrible monsoon rains this year in Pakistan, India, Afghanistan, and China. I plan to write much more about this year's deadly monsoon later this week.

The Great Russian Heat Wave of 2010 chokes Moscow with smoke for a third day
Smoke from wildfires cause by the worst heat wave in Russia's history are choking Moscow for a third straight day today, bringing air pollution levels to three times the safe level and forcing cancellation of dozens of flights. However, air pollution is not quite as bad as it was yesterday, when carbon monoxide levels peaked at 6.5 times the safe level. Visibilities at Moscow's airport were higher today (500+ meters), but temperatures still hit 97°F (36°C). The past 26 days in a row have exceeded 30°C in Moscow, and there is no relief in sight--the latest forecast for Moscow calls for high temperatures near 100°F (37.8°C) for the majority of the coming week. As I reported in Friday's post, the number of deaths in Moscow in July 2010 was about 5,000 more than in July 2009, suggesting that the heat wave has been responsible for thousands of deaths in Moscow alone. I would expect that by the time the Great Russian Heat Wave of 2010 is over, the number of premature deaths caused by the heat wave will approach or exceed the 40,000 who died in the 2003 European Heat Wave. As seen in Figure 3, the Russian heat wave of 2010 is more intense and affects a wider region than the great 2003 European heat wave.


Figure 3. A comparison of August temperatures, the peak of the great European heat wave of 2003 (left) with July temperatures from the Great Russian Heat Wave of 2010 (right) reveals that this year's heat wave is more intense and covers a wider area of Europe. Image credit: NOAA/ESRL.

Next post
I'll have an update Monday.

Jeff Masters

Hurricane

Updated: 1:31 PM GMT on August 08, 2010

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Bermuda eyes a weak Colin; new extreme heat record for Belarus

By: JeffMasters, 4:19 PM GMT on August 07, 2010

Tropical Storm Colin is taking aim at Bermuda, and could bring tropical storm force winds to the island tonight. Colin continues to pass through an unfavorable environment for development, as the storm is being affected by dry being pumped in from an upper-level low pressure system to the west. Wind shear has dropped to about 10 knots, but Colin has not yet been able to take advantage of the low shear. Recent satellite imagery shows that Colin is a disorganized system, with limited heavy thunderstorm activity. What few intense thunderstorms Colin has have been pushed over to the east side of the storm by yesterday's high wind shear, and the rains from these thunderstorms can be seen approaching Bermuda on Bermuda radar.

Forecast for Colin
The latest SHIPS model forecast predicts that wind shear will remain low to moderate today as Colin makes its closest pass by Bermuda. This may allow the storm to intensify to a 50 mph tropical storm before it moves past Bermuda early Sunday morning. The shear will increase again on Sunday as Colin heads out to sea, and it is unlikely that the storm will ever attain hurricane status.


Figure 1. Morning satellite image of Colin.

93L
A tropical wave (Invest 93) about 850 miles west of the Cape Verdes Islands off the coast of Africa is moving northwest at 10 mph. Wind shear is a moderate 10 knots, and is expected to stay in the moderate range the next five days. NHC is giving a 40% chance of this disturbance developing into a tropical depression by Monday morning. The GFS model shows some weak development of 93L occurring early next week. This storm will probably only be a concern to shipping interests. There are no other areas of concern the models are showing for the next seven days.

Belarus records its hottest temperature in history
The European nation of Belarus, on the western border of Russia, recorded its hottest temperature in history yesterday, August 6, when the mercury hit 38.7°C (101.7°F) in Gorky. The previous record was 38.0°C (100.4°F) set at Vasiliyevichy on Aug. 20, 1946.

The Great Russian Heat Wave of 2010 chokes Moscow with smoke for a second day
Smoke from wildfires caused by the worst heat wave in Russia's history have choked Moscow for a second straight day today, bringing air pollution levels to six times the safe mark and forcing cancellation of dozens of flights. Visibilities dropped as low as 325 meters at Moscow's airport today, as temperatures hit 97°F (36°C). The past 25 days in a row have exceeded 30°C (86°F) in Moscow, and there is no relief in sight--the latest forecast for Moscow calls for high temperatures near 100°F (37.8°C) for the majority of the coming week. As I reported in yesterday's post, the number of deaths in Moscow in July 2010 was about 5,000 more than in July 2009, suggesting that the heat wave has been responsible for thousands of deaths in Moscow alone. I would expect that by the time the Great Russian Heat Wave of 2010 is over, the number of premature deaths caused by the heat wave will approach or exceed the 40,000 who died in the 2003 European Heat Wave. As seen in Figure 2, the Russian heat wave of this year is more intense and affects a wider region than the great 2003 heat wave, though the population affected by the two heat waves is probably similar.


Figure 2. A comparison of temperature anomalies for August 2003, the peak of the great European heat wave of that year (left), with July temperature anomalies from the Great Russian Heat Wave of 2010 (right). This year's heat wave in Russia is more intense and covers a wider area of Europe than the 2003 heat wave. The 2003 heat wave caused approximately 40,000 premature deaths. Image credit: NOAA/ESRL.

Commentary
Belarus' new all-time extreme heat record gives the year 2010 the most national extreme heat records for a single year--seventeen. These nations comprise 19% of the total land area of Earth. This is the largest area of Earth's surface to experience all-time record high temperatures in any single year in the historical record. Looking back at the past decade, which was the hottest decade in the historical record, Seventy-five countries set extreme hottest temperature records (33% of all countries.) For comparison, fifteen countries set extreme coldest temperature records over the past ten years (6% of all countries). My source for extreme weather records is the excellent book Extreme Weather by Chris Burt. His new updates (not yet published) remove a number of old disputed records.

Keep in mind that the matter of determining extreme records is very difficult, and it is often a judgment call as to whether an old record is reliable or not. For example, one of 2007's fifteen extreme hottest temperature records is for the U.S.--the 129°F recorded at Death Valley that year. Most weather record books list 1913 as the year the hottest temperature in the U.S. occurred, when Greenland Ranch in Death Valley hit 134°F. However, as explained in a recent Weatherwise article, that record is questionable, since it occurred during a sandstorm when hot sand may have wedged against the thermometer, artificially inflating the temperature. Mr. Burt's list of 225 countries with extreme heat records includes islands that are not independent countries, such as Puerto Rico and Greenland. I thank Mr. Burt and weather record researchers Maximiliano Herrera and Howard Rainford for their assistance identifying this year's new extreme temperature records.

Earth has now seen four consecutive months with its warmest temperature on record, and the first half of 2010 was the warmest such 6-month period in the planet's history. It is not a surprise that many all-time extreme heat records are being shattered when the planet as a whole is so warm. Global warming "loads the dice" to favor extreme heat events unprecedented in recorded history.

National heat records set in 2010
Belarus, on the western border of Russia, recorded its hottest temperature in history on Saturday, August 7, when the mercury hit 38.9°C (102°F) in Gomel. This broke the all-time record for extreme heat set just one day before, the 38.7°C (101.7°F) recorded in Gorky. Prior to 2010, the hottest temperature ever recorded in Belarus was the 38.0°C (100.4°F) in Vasiliyevichy on Aug. 20, 1946.

Ukraine tied its record for hottest temperature in its history when the mercury hit 41.3°C (106.3°F) at Lukhansk on August 1, 2010. Ukraine also reached 41.3°C on July 20 and 21, 2007, at Voznesensk.

Cyprus recorded its hottest temperature in its history on August 1, 2010 when the mercury hit 46.6°C (115.9°F) at Lefconica. The old record for Cyprus was 44.4°C (111.9°F) at Lefkosia in August 1956. An older record of 46.6°C from July 1888 was reported from Nicosia, but is of questionable reliability.

Finland recorded its hottest temperature on July 29, 2010, when the mercury hit 99°F (37.2°C) at Joensuu. The old (undisputed) record was 95°F (35°C) at Jyvaskyla on July 9, 1914.

Qatar had its hottest temperature in history on July 14, 2010, when the mercury hit 50.4°C (122.7°F) at Doha Airport.

Russia had its hottest temperature in history on July 11, when the mercury rose to 44.0°C (111.2°F) in Yashkul, Kalmykia Republic, in the European portion of Russia near the Kazakhstan border. The previous hottest temperature in Russia (not including the former Soviet republics) was the 43.8°C (110.8°F) reading measured at Alexander Gaj, Kalmykia Republic, on August 6, 1940. The remarkable heat in Russia this year has not been limited just to the European portion of the country--the Asian portion of Russia also recorded its hottest temperature in history this year, a 42.7°C (108.9°F) reading at Kara, in the Chita Republic on June 24. The 42.3°C (108.1°F) reading on June 25 at Belogorsk, near the Amur River border with China, also beat the old record for the Asian portion of Russia. The previous record for the Asian portion of Russia was 41.7°C (107.1°F) at Aksha on July 21, 2004.

Sudan recorded its hottest temperature in its history on June 25 when the mercury rose to 49.6°C (121.3°F) at Dongola. The previous record was 49.5°C (121.1°F) set in July 1987 in Aba Hamed.

Niger tied its record for hottest day in history on June 22, 2010, when the temperature reached 47.1°C (116.8°F) at Bilma. That record stood for just one day, as Bilma broke the record again on June 23, when the mercury topped out at 48.2°C (118.8°F). The previous record was 47.1°C on May 24, 1998, also at Bilma.

Saudi Arabia had its hottest temperature ever on June 22, 2010, with a reading of 52.0°C (125.6°F) in Jeddah, the second largest city in Saudi Arabia. The previous record was 51.7°C (125.1°F), at Abqaiq, date unknown. The record heat was accompanied by a sandstorm, which caused eight power plants to go offline, resulting in blackouts to several Saudi cities.

Chad had its hottest day in history on June 22, 2010, when the temperature reached 47.6°C (117.7°F) at Faya. The previous record was 47.4°C (117.3°F) at Faya on June 3 and June 9, 1961.

Kuwait recorded its hottest temperature in history on June 15 in Abdaly, according to the Kuwait Met office. The mercury hit 52.6°C (126.7°F). Kuwait's previous all-time hottest temperature was 51.9°C (125.4°F), on July 27,2007, at Abdaly. Temperatures reached 51°C (123.8°F) in the capital of Kuwait City on June 15, 2010.

Iraq had its hottest day in history on June 14, 2010, when the mercury hit 52.0°C (125.6°F) in Basra. Iraq's previous record was 51.7°C (125.1°F) set August 8, 1937, in Ash Shu'aybah.

Pakistan had its hottest temperature in history on May 26, when the mercury hit an astonishing 53.5°C (128.3°F) at the town of MohenjuDaro, according to the Pakistani Meteorological Department. While this temperature reading must be reviewed by the World Meteorological Organization (WMO) for authenticity, not only is the 128.3°F reading the hottest temperature ever recorded in Pakistan, it is the hottest reliably measured temperature ever recorded on the continent of Asia.

Myanmar (Burma) had its hottest temperature in its recorded history on May 12, when the mercury hit 47°C (116.6°F) in Myinmu, according to the Myanmar Department of Meteorology and Hydrology. Myanmar's previous hottest temperature was 45.8°C (114.4°F) at Minbu, Magwe division on May 9, 1998. According to Chris Burt, author of the authoritative weather records book Extreme Weather, the 47°C measured this year is the hottest temperature in Southeast Asia history.

Ascention Island (St. Helena, a U.K. Territory) had its hottest temperature in history on March 25, 2010, when the mercury hit 34.9°C (94.8°C) at Georgetown. The previous record was 34.0°C (93.2°F) at Georgetown in April 2003, exact day unknown.

The Solomon Islands had their hottest temperature in history on February 1, 2010, when the mercury hit 36.1°C (97°F) at Lata Nendo (Ndeni). The previous record for Solomon Islands was 35.6°C (96.0°F) at Honaiara, date unknown.

Colombia had its hottest temperature in history on January 24, 2010, when Puerto Salgar hit 42.3°C (108°F). The previous record was 42.0°C (107.6°F) at El Salto in March 1988 (exact day unknown).

National cold records set in 2010
One nation has set a record for its coldest temperature in history in 2010. Guinea had its coldest temperature in history in January 9, 2010, when the mercury hit 1.4°C (34.5°F) at Mali-ville in the Labe region.

Next post
I'll have an update Sunday. There are many important weather stories I've neglected to cover of late, such as the floods in Pakistan, which I hope to talk about in the coming week.

Jeff Masters

Heat Hurricane

Updated: 3:21 PM GMT on August 09, 2010

Permalink

Colin takes aim at Bermuda; the Great Russian Heat Wave of 2010: 102°F in Moscow

By: JeffMasters, 2:45 PM GMT on August 06, 2010

A reborn Tropical Storm Colin is taking aim at Bermuda, and should bring tropical storm force winds to the island by Saturday afternoon. Colin continues to pass through an unfavorable environment for development--an upper-level low pressure system with dry air and high wind shear. High wind shear of 20 - 25 knots has exposed the surface circulation to view, as seen in recent satellite imagery. Colin's heavy thunderstorm activity is all on the east side of the storm, and the associated rains can now be seen approaching the island on Bermuda radar.

Forecast for Colin
The latest SHIPS model forecast predicts that wind shear will drop to the low to moderate range, 5 - 15 knots, tonight through Saturday afternoon. This relaxation of shear prompts the intensity models to predict that Colin will strengthen to a 50 - 70 mph tropical storm by Sunday. With the forecast path of the storm predicted to take Colin just west of Bermuda, the island will be in the strong right front quadrant of the storm, and may see wind gusts in excess of hurricane force, 74 mph. After its encounter with Bermuda, Colin will head towards Newfoundland, and it is possible the storm could bring tropical storm force winds to the island on Monday. However, wind shear will be on the increase again beginning Saturday night, and it is unlikely Colin will be a hurricane when it makes it closest approach to Newfoundland.


Figure 1. Morning satellite image of Colin.

93L
A tropical wave (Invest 93) about 700 miles west of the Cape Verdes Islands off the coast of Africa is moving northwest at 10 mph. Wind shear is a moderate 10 - 20 knots over 93L, which is low enough to allow some slow development. This system currently does not appear to be a concern to any land areas over the next seven days. NHC is giving a 40% chance of this disturbance developing into a tropical depression by Sunday morning. The GFS and NOGAPS models predict 93L will become a tropical depression.


Figure 2. Smoke from fires in Russia on August 4 covers an area over 3,000 km (1860 miles) across. If the smoke were in the United States, it would extend approximately from San Francisco to Chicago. Visibility in Moscow dropped to 20 meters (0.01 miles) on August 4, and health officials warned that everyone, including healthy people, needed to take preventative measures such as staying indoors or wearing a mask outdoors. Image credit: NASA.

The Great Russian Heat Wave of 2010 continues
One of the most remarkable weather events of my lifetime is unfolding this summer in Russia, where an unprecedented heat wave has brought another day of 102°F heat to the nation's capital. At 3:30 pm local time today, the mercury hit 39°C (102.2°F) at Moscow's Domodedovo Airport. Moscow had never recorded a temperature exceeding 100°F prior to this year, and today marks the second time the city has beaten the 100°F mark. The first time was on July 29, when the Moscow observatory recorded 100.8°C and Baltschug, another official downtown Moscow weather site, hit an astonishing 102.2°F (39.0°C). Prior to this year, the hottest temperature in Moscow's history was 37.2°C (99°F), set in August 1920. The Moscow Observatory has now matched or exceeded this 1920 all-time record five times in the past eleven days, including today. The 2010 average July temperature in Moscow was 7.8°C (14°F) above normal, smashing the previous record for hottest July, set in 1938 (5.3°C above normal.) July 2010 also set the record for most July days in excess of 30°C--twenty-two. The previous record was 13 such days, set in July 1972. The past 24 days in a row have exceeded 30°C in Moscow, and there is no relief in sight--the latest forecast for Moscow calls for high temperatures near 100°F (37.8°C) for the next seven days. It is stunning to me that the country whose famous winters stopped the armies of Napoleon and Hitler is experiencing day after day of heat near 100°F, with no end in sight.

Thousands of deaths, severe fires, and the threat of radioactive contamination
The extreme heat has led to thousands of premature deaths in Russia. According to Yevgenia Smirnova, an official from the Moscow registry office, "We recorded 14,340 deaths in Moscow in July, that is 4,824 deaths more than in July, 2009." Undoubtedly thousands of additional premature deaths have occurred in the rest of Russia as a result of the heat. The heat has also caused the worst drought conditions in European Russia in a half-century, prompting the Russian government to suspend wheat exports. The drought has caused extreme fire danger over most of European Russia (Figure 3), and fires in Russia have killed at least 50 people in the past week and leveled thousands of homes. The fires are the worst since 1972, when massive forest and peat bog fires burned an area of 100,000 square km and killed at 104 people in the Moscow region alone. Smoke from the current fires spans a region over 3,000 km (1,860 miles) from east to west, approximately the distance from San Francisco to Chicago. Dozens of flights were canceled at Moscow's airports today, thanks to visibilities of 300 meters in smoke. Also of concern is fires that have hit the Bryansk region of western Russia, which suffered radioactive contamination from the Chernobyl nuclear disaster in nearby Ukraine. There are fears that fires may burn through the contaminated area, releasing harmful radiation into the atmosphere.


Figure 3. Fire danger in Russia for August 5, 2010. Extreme fire danger (Category 5, red colors) was seen over much of the European portion of Russia. Image credit: Hydrometcentre, Russia.

Why has Russia's heat wave been so long and intense?
Dr. Rob Carver has done a detailed analysis of the remarkable Russian heat wave in his latest post, The Great Russian Heat Wave of July 2010. A persistent jet stream pattern has set up over Europe, thanks to a phenomena known as blocking. A ridge of high pressure has remained anchored over Russia, and the hot and dry conditions have created helped intensify this ridge in a positive feedback loop. As a result, soil moisture in some portions of European Russia has dropped to levels one would expect only once every 500 years.

Next update
I'll have an update on Saturday morning.

Jeff Masters

Heat Hurricane

Updated: 7:46 PM GMT on August 06, 2010

Permalink

Colin ready to re-form; TSR keeps their Atlantic hurricane forecast numbers high

By: JeffMasters, 1:54 PM GMT on August 05, 2010

The remains of Tropical Storm Colin continue to generate heavy thunderstorm activity over the waters a few hundred miles northeast of Puerto Rico. Colin's remains are in a rather unfavorable environment for re-development, since the storm is passing beneath an upper-level low pressure system with dry air and high wind shear. Despite the high wind shear of 20 - 25 knots, Colin's remains have grown more organized during the past day, and a low-level circulation has formed. A pass of the Windsat satellite last night revealed that ex-Colin is already generating tropical storm force winds of 40 mph in isolated regions. Recent satellite imagery shows that heavy thunderstorm activity has increased in intensity and areal coverage this morning, and a low level circulation that may or may not persist has formed near 23.5N 65.5W (Figure 1.)

Forecast for Colin
The latest SHIPS model forecast predicts that wind shear will drop from 15 - 25 knots today to a moderate 10 - 20 knots on Friday. This relaxation of shear prompts most of the major models to predict re-development of Colin sometime in the next three days. NHC is giving Colin's remain a 50% chance of developing into a tropical depression by Saturday morning. A major trough of low pressure will move off the U.S. East Coast on Friday, and this trough will pull Colin to the north and cause it to slow down. All of the major forecast models are predicting that the trough of low pressure will be strong enough to fully recurve Colin out to sea early next week. Colin's remains may pass close to Bermuda on Saturday, with the latest 06Z (2am EDT) run of the GFDL model predicting that Bermuda will experience tropical storm force winds on Saturday as Colin passes to the west of the island. The Hurricane Hunters are scheduled to investigate Colin's remains at 2 pm EDT this afternoon. It currently appears that Colin will only be a threat to Bermuda and Newfoundland.


Figure 1. Morning satellite image of Colin's remains show a low-level circulation, exposed to view, has formed at the edge of a region of heavy thunderstorms.

92L
A tropical wave (Invest 92) a few hundred miles south of Jamaica is moving west at 15 - 20 mph. This wave is over warm water and is experiencing low wind shear of 5 - 10 knots, and could show some development over the next two days. However, the wave's rapid westward motion should bring it ashore over Nicaragua and Honduras on Friday and the Yucatan Peninsula on Saturday, and 92L probably does not have enough time over water to develop into a tropical depression. NHC is giving a 10% chance of this disturbance developing into a tropical depression by Friday morning.

Elsewhere in the tropics
The GFS model is predicting that a tropical wave that moved off the coast of Africa yesterday will develop into a tropical depression early next week. None of the other models is showing any obvious tropical cyclone development over the coming week. The current phase of the Madden-Julian Oscillation (MJO) over the Atlantic favors upward motion and enhanced probabilities of tropical storm formation, so it would not be a surprise to see a new tropical depression form next week between Africa and the Lesser Antilles Islands.

TSR keeps their forecast numbers for the coming hurricane season high
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) joins CSU in calling for a very busy Atlantic hurricane season. The latest TSR forecast issued August 4 calls for 17.8 named storms, 9.7 hurricanes, 4.5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 183% of average (assuming an ACE of 101 is average.) These storm numbers are a slight drop from their July 6 forecast of 19.1 named storms, 10.4 hurricanes, and 4.8 intense hurricanes, but this is still a very aggressive forecast. The 50-year average is 10 named storms, 6 hurricanes, and 2 intense hurricanes. TSR predicts a 96% chance that this season will have an above-average ACE index, and only 4% chance it will be near normal. TSR rates their skill level for August forecasts as 51% above chance at forecasting the number of named storms, 64% skill for hurricanes, and 47% skill for intense hurricanes.

TSR projects that 5.7 named storms will hit the U.S., with 2.6 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. TSR's skill in making these August forecasts for U.S. landfalls is 19% - 23% above chance. They give an 89% chance that the U.S. landfalling ACE index will be above average. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.8 named storms, 0.8 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for keeping their numbers high: below-average trade winds and near-record warm sea surface temperatures in the tropical Atlantic. TSR expects trade winds in the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean) to be 1.53 meters per second (about 3.4 mph) slower than average in this region, which would create more spin for developing storms, and allow the oceans to heat up, due to decreased mixing of cold water from the depths and reduced evaporational cooling.

Forecast numbers for the coming hurricane season
Here are the number of Atlantic named storms, hurricanes, and intense hurricanes predicted by the various forecast groups in their late May or early June forecasts:

23 named storms: PSU statistical model
20 named storms: UKMET GloSea dynamical model
18.5 named storms, 11 hurricanes, 5 major hurricanes: NOAA hybrid statistical/dynamical model technique
18 named storms, 10 hurricanes, 5 intense hurricanes: CSU statistical model (Phil Klotzbach/Bill Gray)
17.7 named storms, 9.5 hurricanes, 4.4 intense hurricanes: Tropical Storm Risk (TSR), hybrid statistical/dynamical model technique
17 named storms, 10 hurricanes: FSU COAPS dynamical model
10 named storms, 6 hurricanes, 2 intense hurricanes: climatology

And here are the new late July/early August forecast numbers so far:

15 named storms, 8 hurricanes: FSU COAPS dynamical model (July 15 forecast)
18 named storms, 10 hurricanes, 5 intense hurricanes: CSU statistical model (Phil Klotzbach/Bill Gray)
17.8 named storms, 9.7 hurricanes, 4.5 intense hurricanes: Tropical Storm Risk (TSR), hybrid statistical/dynamical model technique (Note: TSR had higher numbers of 19.1, 10.4, and 4.8 in their July 6 forecast)

This season has had three named storms so far (Alex, Bonnie, and Colin.) It will be difficult to have a season with 19 or more named storms, since the four seasons that had at least 19 named storms all had at least five named storms by this point (August 4.) These four seasons were 1887, 1933, 1995, and 2005.

Next update
I'll have an update on Friday morning.

Jeff Masters

Hurricane

Permalink

CSU leaves their hurricane forecast unchanged; 92L and Colin's remains worth watching

By: JeffMasters, 2:38 PM GMT on August 04, 2010

Tropical Storm Colin was ripped apart by wind shear yesterday, and the storm's remnants are passing just north of the northernmost Lesser Antilles Islands today. Most of the heaviest thunderstorms are passing north of the islands, as seen on Guadeloupe radar. Long range radar out of Puerto Rico also shows this. Colin's remains are in a rather unfavorable environment for re-development, since the disturbance is passing beneath an upper-level low pressure system with dry air and high wind shear. Wind shear is a high 20 - 25 knots over Colin's remains this morning. Recent satellite imagery shows that heavy thunderstorm activity has increased in intensity and areal coverage over the past few hours, though, and Colin's remnants will need to be monitored for re-development.

Forecast for Colin's remains
The latest SHIPS model forecast predicts that wind shear will drop from 15 - 25 knots today to a moderate 15 - 20 knots on Thursday. Wind shear will continue to decline over the weekend, and this relaxation of shear prompts most of the major models to predict re-development of Colin sometime in the next four days. NHC is giving Colin's remain a 20% chance of developing into a tropical depression by Friday morning. A major trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough will pull Colin to the northwest and cause it to slow down. By Friday, Colin will be moving at half of its current speed. All of the major forecast models are predicting that the trough of low pressure will be strong enough to fully recurve Colin out to sea early next week. Colin's remains may pass close to Bermuda on Saturday, with the latest 06Z (2am EDT) run of the GFDL model predicting that Bermuda will experience tropical storm force winds on Saturday as Colin passes to the west of the island. The Hurricane Hunters are scheduled to investigate Colin's remains at 8pm EDT tonight. It currently appears that Colin will only be a threat to Bermuda and Canada.


Figure 1. Morning satellite image of Colin's remains and Invest 92L.

92L
A tropical wave (Invest 92) in the south-central Caribbean is moving west at 15 - 20 mph. This wave is over warm water and is experiencing low wind shear of 5 - 10 knots, and could show some development over the next two days. However, the wave's rapid westward motion should bring it ashore over Nicaragua and Honduras on Friday, or the Yucatan Peninsula on Saturday, and 92L probably does not have enough time over water to develop into a tropical depression. NHC is giving a 20% chance of this disturbance developing into a tropical depression by Friday morning. This storm was being tagged as 98L yesterday; I'm not sure why it is being called 92L today.

CSU's forecast numbers for the coming hurricane season remain unchanged
A very active Atlantic hurricane season is on tap for 2010, according to the seasonal hurricane forecast issued today, August 4, by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team continues to call for 18 named storms, 10 hurricanes, 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) index 185% of average. These are the same numbers as their June 2 forecast. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast continues to call for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (50% chance, 31% chance is average) and the Gulf Coast (49% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 64% (42% is average.)

The forecasters cited four main reasons for an active season:

1) Moderate La Niña conditions should be present during the most active portion of this year's hurricane season (August - October). This should lead to reduced levels of vertical wind shear compared with what was witnessed in 2009.

2) Current SST anomalies are running at near-record warm levels. These very warm waters are associated with dynamic and thermodynamic factors that are very conducive for an active Atlantic hurricane season.

3) Very low sea level pressures prevailed during June and July over the tropical Atlantic. Weaker high pressure typically results in weaker trade winds that are commonly associated with more active hurricane seasons.

4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80 - 85 percent of normalized hurricane damage.

Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this summer. Those four years were 2005, the worst hurricane season of all time; 1998, which featured 3 major hurricanes, including Category 5 Hurricane Mitch; 1952, a relatively average year that featured just 7 named storms, but 3 major hurricanes; and 1958, a severe season with 5 major hurricanes. The mean activity for these five years was 17 named storms, 11 hurricanes, and 5 intense hurricanes, almost the same as the 2010 CSU forecast.

How accurate are the August forecasts?
The August forecasts by the CSU team over the past 12 years have had a skill 21% - 44% higher than a "no-skill" climatology forecast for number of named storms, hurricanes, intense hurricanes, and the ACE index (Figure 2). This is a good amount of skill for a seasonal forecast, and these August forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. This year's August forecast uses a new formula, so we don't have any history on how the technique has behaved in the past. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.61 to 0.65 for their previous August forecasts using different techniques, which is respectable.


Figure 2. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. The British firm Tropical Storm Risk (TSR) will issue their outlook for the 2010 Atlantic hurricane season on June 4. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

The British private forecasting firm Tropical Storm Risk, Inc. (TSR) is scheduled to release their August forecast later today. NOAA will also be issuing their August forecast sometime in the next week.

This season has had three named storms so far (Alex, Bonnie, and Colin.) It will be difficult to have a season with 19 or more named storms, since the four seasons that had at least 19 named storms all had at least five named storms by this point (August 4.) These four seasons were 1887, 1933, 1995, and 2005.

Next update
I'll have an update on Thursday morning.

Jeff Masters

Hurricane

Updated: 8:28 PM GMT on January 03, 2012

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Colin arrives; extreme heat records fall for Ukraine and 5 U.S. cities

By: JeffMasters, 12:16 PM GMT on August 03, 2010

Tropical Storm Colin has made its debut over the Atlantic, but does not appear to be a threat to any land areas over the next five days. Satellite imagery shows that Colin is intensifying, as both the intensity and areal extent of heavy thunderstorms has increased over the past few hours. A respectable low-level spiral band is developing to the north of the center, and upper-level outflow is beginning to appear on all sides of the storm. Colin is a very small storm, and its tropical storm force winds extend out just 30 miles from the center. Colin passed about 50 miles south of Buoy 41041 early this morning, and generated top sustained winds of 27 mph at the buoy. There is some dry air associated with the Saharan Air Layer (SAL) to the northwest of Colin, but this dry air is not getting entrained into Colin at present. Wind shear is a low 5 - 10 knots and sea surface temperatures are a very warm 28 - 29°C, so continued development is likely today. The main negative for development appears to be the storm's small size, which makes it vulnerable to modest increases in wind shear or dry air entrainment. The first flight of the Hurricane Hunters into Colin is scheduled for Wednesday morning.


Figure 1. Morning satellite image of Tropical Storm Colin.

Forecast for Colin
The latest 6Z (2am EDT) models are fairly unified taking Colin to the west-northwest at 20 - 25 mph for the next three days. This would bring squalls from the storm's outer rainbands to the northern Lesser Antilles Islands, such as Antigua and Barbuda, by Wednesday afternoon. The center of Colin should pass to the northeast of the islands, and the storm is small enough that the islands are unlikely to experience tropical storm force winds. As Colin makes its closest approach to the Lesser Antilles on Wednesday night, the storm will begin to encounter strong upper-level westerly winds associated with the counter-clockwise flow of air around an upper-level low pressure system centered between Bermuda and Puerto Rico. The latest SHIPS model forecast predicts that these winds will cause wind shear to rise to the moderate level, 10 - 20 knots, by Wednesday morning, and to the high level, 20 - 30 knots, by Thursday. There is considerable dry air associated with the upper level low that should cause problems for Colin, as well. The high wind shear and dry air should weaken Colin. NHC is giving Colin a 25% chance of attaining hurricane status this week.

A trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough will pull Colin to the northwest and cause it to slow down on Wednesday. By Friday, Colin will be moving at half of its current speed. It is unclear if the trough of low pressure will be strong enough to fully recurve Colin out to sea late this week. Some of the models predict Colin will not recurve out to sea, and that high pressure will build back in this weekend, forcing Colin towards the U.S. East Coast. A second trough of low pressure is predicted to move off the U.S. East Coast next Monday, so Colin will have a second opportunity to recurve out to sea then. It is possible that Colin could make landfall along the U.S. East Coast or in the Canadian Maritime provinces 7 - 10 days from now, though it is still too early to assess the risk of this happening, nor how strong Colin might be.

Ukraine ties its record for hottest temperature in history
On August 1, Ukraine tied its record for hottest temperature in its history when the mercury hit 41.3°C (106.3°F) at Lukhansk. The Ukraine also reached 41.3°C on July 20 and 21, 2007, at Voznesensk. Sixteen of 225 nations on Earth have set extreme highest temperature in history records this year, the most of any year. The year 2007 is in second place, with fifteen such records.

Five major U.S. cities record their warmest month in history during July
July 2010 was the warmest month in history for five U.S. cities:

Las Vegas, NV: 96.2°F (old record: 95.3°F, July 2005).
Atlantic City, NJ: 79.8°F (old record: 78.7°F, July 1983)
Washington, D.C.: 83.1°F (tied with July 1993)
Baltimore, MD: 81.5°F (tied with July 1995)
Trenton, NJ: 80.5°F (tied with July 1955)

Also, in June, Miami, FL recorded its warmest month in history: 85.6°F (old record: 85.4°F in June 1998.)

Commentary
None of the 303 major U.S. cities listed in the records section of Chris Burt's book Extreme Weather has set a coldest month in history record since 1994 (these 303 cites were selected to represent a broad spectrum of U.S. climate zones, are not all big cities, have a good range of elevations, and in most cases have data going back to the 1880s.) There were just three such records (1% of the 303 major U.S. cities) set in the past twenty years, 1991 - 2010. In contrast, 97 out of 303 major U.S. cities (32%) set records for their warmest month in history during the past twenty years. It is much harder to set a coldest month in history record than a coldest day in history record in a warming climate, since it requires cold for an extended period of time--not just a sudden extreme cold snap.

Are the pattern of U.S. temperature records due to the Urban Heat Island effect?
Is the huge disparity between extreme heat records and extreme cold records in the U.S. due to global warming, or the Urban Heat Island effect? The Urban Heat Island (UHI) effect occurs when development of former natural areas into pavement and buildings allows more heat to be trapped in cities, particularly at night. During the day, the UHI effect often leads to a slight cooling, since it can increase the amount of turbulence, allowing cooler air to get mixed down to the surface. For example, Moreno-Garcia (1994) found that Barcelona, Spain was 0.2°C cooler for daily maxima and 2.9°C warmer for minima than a nearby rural station.

However, temperature records are typically taken in parks and airports removed from the main heat-trapping areas of cities, and are not as strongly affected as one might expect. There are several reasons for this. One is that when tall buildings are present, they tend to block the view to the sky, meaning that not as much heat can escape upwards. In addition, the presence of moist vegetation keeps the atmosphere moister in park-like areas (which include the grassy fields near airports where temperature measurements are taken). This extra moisture helps cool the atmosphere on a local scale of tens of meters, due to latent heat effects (the energy required to convert liquid water to water vapor). Peterson (2003) found that "Contrary to generally accepted wisdom, no statistically significant impact of urbanization could be found in annual temperatures." The study used satellite-based night-light detection to identify urban areas. Recent research by Spronken-Smith and Oke (1998) concluded that there was a marked park cool island effect within the Urban Heat Island. They found that parks in typical cities in the U.S. have temperatures 1 - 2°C cooler than the surrounding city--and sometimes more than 5°C cooler. While the Urban Heat Island effect probably has contributed to some of the reduction in record low temperatures in the U.S. in the past decade, research by Parker (2004, 2006) and Peterson (2003) theorizes that Urban Heat Island effect is a factor ten or more less important than rising temperatures due to global warming.

Chris Burt wrote me yesterday about Las Vegas' all-time warmest month record set in July. He noted that none of the sites nearby Las Vegas' McCarran Airport (where the official obs are kept) came close to setting a warmest month in history record. McCarran Airport has set new warmest month in history records in 2003, 2005, and now 2010. These two facts make us suspect that in the case of Las Vegas, an urban heat island effect may be contributing to the spate of recent warmest month in history records there. The heat records for Atlantic City, Washington D.C., Baltimore, and Trenton do not appear to have as much of a UHI influence, since record highs were set over such a large area of the mid-Atlantic in July.

Is the Urban Heat Island effect partially responsible for global warming?
Global warming is affecting the entire Earth, including rural areas far from cities, and the 70% of the world covered by ocean. Thus, the Urban Heat Island effect--if not corrected for--can cause only a small impact on the global temperature figures. Since the Urban Heat Island is corrected for, the impact on the observed global warming signal should be negligible. For instance, NASA uses satellite-derived night light observations to classify stations as rural and urban and corrects the urban stations so that they match the trends from the rural stations before gridding the data. Other techniques (such as correcting for population growth) have also been used. Despite these corrections, and the fact that the Urban Heat Island effect impacts only a relatively small portion of the globe, global warming skeptics have persistently used the Urban Heat Island effect to attack the validity of global warming. There are no published peer-reviewed scientific studies that support these attacks.

References
Parker, D.E., 2004, "Large-Scale Warming is not Urban", Nature 432, 290, doi:10.1038/432290a, 2004.

Parker, D.E., 2006, "A Demonstration that Large-Scale Warming is not Urban", J. Climate 19, pp2882-2986, 2006.

Peterson, T.C., "Assessment of urban versus rural in situ surface temperatures in the contiguous United States: No difference found", Journal of Climate, 16, 2941-2959, 2003.

Spronken-Smith, R. A., and T. R. Oke, 1998: "The thermal regime of urban parks in two cities with different summer climates. Int. J. Remote Sens., 19, 20852104.

The surface temperature record and the urban heat island, realclimate.org post, 2004.

Next update
I have a series of meetings today that will probably keep me from making another post, and keep me from doing my weekly Internet radio show, Hurricane Haven. I'll be back Wednesday morning, at the latest, with a new post.

Jeff Masters

Heat Hurricane

Updated: 6:31 PM GMT on August 03, 2010

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Tropical Depression Four arrives

By: JeffMasters, 7:23 PM GMT on August 02, 2010

Tropical Depression Four has made its debut over the mid-Atlantic Ocean, about 1300 miles east of the Lesser Antilles Islands. TD 4 is a small storm with very limited heavy thunderstorm activity, and is not very impressive at present. Wind shear is a low 5 - 10 knots, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of TD 4 to allow further development, though. The main negative for development appears to be the storm's small size, which makes it vulnerable to modest increases in wind shear or dry air entrainment. Satellite imagery shows that TD 4 is gradually developing low-level spiral bands, but the intensity and areal extent of heavy thunderstorms has not increased over the past few hours. Upper-level outflow is not apparent yet.


Figure 1. Afternoon satellite image of TD 4.

Forecast for TD 4
The latest 12Z (8am EDT) models are fairly unified taking TD 4 to the west-northwest at 15 - 20 mph for the next three days. This would bring squalls from the storm's outer rainbands to the northern Lesser Antilles Islands, such as Antigua and Barbuda, by Wednesday afternoon. The center of TD 4 should pass to the northeast of the islands. A more southerly track through Puerto Rico, as predicted by the Canadian model, cannot be ruled out, though. As TD 4 makes its closest approach to the Lesser Antilles on Wednesday night, the storm will begin to encounter strong upper-level westerly winds associated with the counter-clockwise flow of air around an upper-level low pressure system centered between Bermuda and Puerto Rico. The latest SHIPS model forecast predicts that these winds will cause wind shear to rise to the moderate level, 10 - 20 knots, by Tuesday night, and to the high level, 20 - 30 knots, by Wednesday. There is a great deal of dry air associated with the upper level low that should cause problems for TD 4, as well. The high wind shear and dry air should greatly weaken and may destroy TD 4 late this week. NHC is giving TD 4 a 20% chance of attaining hurricane status by 8am EDT on Thursday. I think the storm will probably become Tropical Storm Colin tonight, and peak in strength on Wednesday as a 55 - 65 mph tropical storm. I agree that a 20% chance of it reaching hurricane strength is a reasonable forecast.

A trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough may be strong enough to recurve TD 4 far enough to the northwest that the storm will threaten Bermuda. The GFDL model predicts TD 4 could pass very near to Bermuda on Saturday. It is uncertain at this time if the trough will be strong enough to recurve TD 4 all the way out to sea early next week, or leave the storm behind to potentially move westward again into the U.S. East Coast. The amount of wind shear that might be present early next week is also highly uncertain.

Next update
I'll have an update Tuesday morning by 8:30 EDT.

Jeff Masters

Hurricane

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91L near tropical depression status

By: JeffMasters, 2:08 PM GMT on August 02, 2010

A tropical wave near 12N 41W, midway between Africa and the Lesser Antilles Islands, is very close to being a tropical depression. NHC labeled this system Invest 91L yesterday, and is giving it a 90% chance of developing into a tropical depression by 8am Wednesday. Wind shear is a low 5 - 10 knots, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of 91L to potentially allow further development. The main negative for development appears to be the storm's small size, which makes it vulnerable to modest increases in wind shear or dry air entrainment. A Windsat pass from 5am EDT this morning did not show a closed circulation. Satellite imagery shows that the intensity and areal extent of 91L's heavy thunderstorms is very limited, but that a closed surface circulation may be close to forming. Low-level spiral bands and upper-level outflow are not apparent yet.


Figure 1. Morning satellite image of Invest 91L.

Forecast for 91L
There is modest model support for 91L developing into a tropical depression. Three out of six of our reliable models for forecasting tropical cyclone genesis predict 91L will develop into a tropical depression by Tuesday or Wednesday. A west-northwest motion at 10 -15 mph is predicted, which should carry 91L a few hundred miles northeast of the northernmost Lesser Antilles Islands. However, it is possible that 91L would track over the northernmost Lesser Antilles Islands, as predicted by the Canadian model. Squalls from the outer rainbands of 91L may affect islands such as Antigua and Barbuda as early as Wednesday afternoon. As 91L makes its closest approach to the Lesser Antilles on Wednesday, the storm will begin to encounter strong upper-level westerly winds associated with the counter-clockwise flow of air around an upper-level low pressure system centered between Bermuda and Puerto Rico. The latest SHIPS model forecast predicts that these winds will cause wind shear to rise to the moderate level, 10 - 20 knots, by Tuesday night, and to the high level, 20 - 30 knots, by Wednesday. There is also a great deal of dry air associated with the upper level low that may cause problems for 91L. The high wind shear and dry air should weaken and possibly destroy 91L late this week.

A trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough may be strong enough to recurve 91L far enough to the northwest that the storm will threaten Bermuda. The HWRF and ECMWF models predict 91L could pass very near to Bermuda on Saturday. It is uncertain at this time if the trough will be strong enough to recurve 91L all the way out to sea early next week, as predicted by the GFS model, or leave 91L behind to potentially move westward again into the U.S. East Coast, as predicted by the Canadian model. The amount of wind shear that might be present early next week is also highly uncertain.

Cyprus records its hottest temperature in history yesterday
The island of Cyprus recorded its hottest temperature in its history on August 1, 2010 when the mercury hit 46.6°C (115.9°F) at Lefconica. The old record for Cyprus was 44.4°C (111.9°F) at Lefkosia in August 1956. An older record of 46.6°C from July 1888 was reported from Nicosia, but is of questionable reliability.

The year 2010 is now tied with 2007 as the year with the most national extreme heat records--fifteen. There has been one country that has recorded its coldest temperature on record in 2010; see my post last week for a list of the 2010 records. My source for extreme weather records is the excellent book Extreme Weather by Chris Burt. His new updates (not yet published) remove a number of old disputed records. Keep in mind that the matter of determining extreme records is very difficult, and it is often a judgment call as to whether an old record is reliable or not. For example, one of 2007's fifteen extreme hottest temperature records is for the U.S.--the 129°F recorded at Death Valley that year. Most weather record books list 1913 as the year the hottest temperature in the U.S. occurred, when Greenland Ranch in Death Valley hit 134°F. However, as explained in a recent Weatherwise article, that record is questionable, since it occurred during a sandstorm when hot sand may have wedged against the thermometer, artificially inflating the temperature. Mr. Burt's list of 225 countries with extreme heat records includes islands that are not independent countries, such as Puerto Rico and Greenland. Seventy four extreme hottest temperature records have been set in the past ten years (33% of all countries.) For comparison, 14 countries set extreme coldest temperature records over the past ten years (6% of all countries). I thank Mr. Burt and weather record researchers Maximiliano Herrera and Howard Rainford for their assistance identifying this year's new extreme temperature records.

Next update
I'll have an update later today if 91L develops into a TD.

Jeff Masters

Hurricane

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Lesser Antilles may see a tropical storm late this week

By: JeffMasters, 1:51 PM GMT on August 01, 2010

A concentrated area of intense thunderstorms near 9N 36W, midway between Africa and the Lesser Antilles Islands, has become more organized this morning. NHC has labeled this system Invest 91L, and is giving it a 60% chance of developing into a tropical depression by 8am Tuesday. Wind shear is a moderate 10 - 20 knots, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of 91L to potentially allow further development. The main negatives for development are the current phase of the Madden-Julian Oscillation, which favors downward motion over the tropical Atlantic, and the fact that 91L is too close to the Equator to take much advantage of the Earth's spin to get spinning. Last night's ASCAT pass of the region did show a large region of westerly winds south of 91L, indicating that a surface circulation is trying to form. Satellite imagery shows that the intensity and areal extent of 91L's heavy thunderstorms is increasing. However, there are no signs of a surface circulation, and low-level spiral bands and upper-level outflow are not apparent yet.

Forecast for 91L
There is strong model support for 91L developing into a tropical depression. The GFS, ECMWF, NOGAPS, and UKMET models all develop 91L into a tropical depression by Tuesday or Wednesday. A west to west-northwest motion is predicted, and residents of the Lesser Antilles Islands should anticipate the possibility of a tropical storm arriving in the islands as early as Thursday. It is possible that 91L would pass northeast of the islands, as predicted by the UKMET model, and it is too early to speculate on which of the islands is at most risk. As the storm approaches the Lesser Antilles late this week, 91L will encounter a strong upper-level low pressure system centered north of Puerto Rico. This upper-level low will likely bring high levels of wind shear to the waters just north of Puerto Rico and Hispaniola. Thus, if 91L stays to the south, in the Caribbean, it is far more likely to attain hurricane status than if it pushes north of the Caribbean. As always, long range forecasts of this sort are speculative, and it is too early to reliably say what the long-term risks of 91L becoming a hurricane are. The latest intensity forecast from the SHIPS model shows 91L peaking in strength four days from now, then weakening as it encounters the high wind shear area north of Puerto Rico.


Figure 1. Morning satellite image of Invest 91L.

Next update
I'll have an update Monday morning.

Jeff Masters

Hurricane

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.