Dr. Jeff Masters' WunderBlog

91L Near Tropical Depression Status; Entire SE U.S. Coast Could be Impacted

By: JeffMasters, 3:31 PM GMT on June 30, 2014

An area of disturbed weather over the warm waters of the Gulf Stream, located about 130 miles east-northeast of Melbourne, Florida on Monday morning (Invest 91L), has grown more organized this morning. Surface pressures are falling, and 91L is close to tropical depression status. Satellite loops on Monday morning showed 91L had a well defined surface circulation, with heavy thunderstorms building and steadily organizing into spiral bands. Long-range radar out of Melbourne, Florida showed these bands were already affecting the coast of Central Florida. Sea surface temperatures in this region were about 1°C above average, 27 - 28°C. The counter-clockwise circulation of an upper level high pressure over Florida was bringing northerly winds over 91L at high altitude, and these winds were creating light wind shear of 5 - 10 knots. However, water vapor satellite loops show that the atmosphere has dried noticeably to the north of 91L since Sunday, and the northerly winds are driving this dry air in the heart of the storm. This dry air is interfering with development and keeping any heavy thunderstorms from developing on the north side of the circulation. The Hurricane Hunters will investigate 91L on Monday afternoon.


Figure 1. Water vapor satellite image of 91L taken at 10:45 am EDT Monday June 30, 2014. A large area of dry air (black colors) was to the north of the system, and was interfering with development. Image credit: NOAA/NESDIS.


Figure 2. Wind forecast for 11 am Thursday, July 3, 2014, as made by the 06Z Monday June 30, 2014 run of the GFS model (left) and 00Z Monday run of the European model (right.) Both models are predicting that 91L will become a tropical storm and threaten the South Carolina coast on Thursday.

Forecast for 91L
Steering currents are weak off of the Southeast U.S. coast, but the models are in good agreement on the track of 91L. The disturbance should continue a slow southward to southwesterly motion on Monday, which would bring the storm very close to the coast of Florida by Tuesday. The system is expected to meander near the coast of Florida on Tuesday and Wednesday, before a trough of low pressure to the north begins pulling the system to the north and northeast on Thursday and Friday. Heavy rains of at least 2 - 4" will likely affect the Northwest Bahamas and eastern coast of Florida Monday through Wednesday. Heavier rains of 4 - 8" are likely, since I expect 91L to develop into a tropical depression on Monday or Tuesday. Heavy rains of 2 - 4" will spread to coastal Georgia, South Carolina, and North Carolina on Thursday and Friday, and tropical storm conditions are possible along the South Carolina and North Carolina coasts on Thursday and Friday. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave 91L 2-day and 5-day development odds of 60% and 80%, respectively. The 12Z Monday run of the SHIPS model shows the atmosphere surrounding 91L will get even drier this week, with the wind shear staying light to moderate, 5 - 15 knots. This dry air, in combination with potentially moderate wind shear, will slow development of 91L. If 91L makes landfall over Florida on Tuesday or Wednesday, interaction with land will also interfere with development. However, the storm will be over the warm waters of the Gulf Stream when the center is offshore, and we should not dismiss the possibility that 91L could reach Category 1 hurricane strength late this week, as some of the members of the 00Z Monday morning European model ensemble were suggesting. It is more likely, though, that 91L will struggle with land interaction, dry air and wind shear, and be at worst a medium-strength tropical storm named Arthur with 50 - 55 mph winds as it brushes the coasts of South Carolina and North Carolina on Thursday and Friday. There is a lot of uncertainty with this forecast, so stay tuned.

Jeff Masters

Hurricane

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91L Growing More Organized; Will Bring Heavy Rains to Florida and the Bahamas

By: JeffMasters, 2:45 PM GMT on June 29, 2014

An area of disturbed weather over the warm waters of the Gulf Stream, about 230 miles east of Jacksonville, Florida (Invest 91L) has grown more organized since Saturday, and is a threat to develop into a tropical depression early this week. Satellite loops on Sunday morning showed 91L with only a modest amount of heavy thunderstorm activity, but the system had a pronounced spin, and the heavy thunderstorms were organizing into spiral bands. Long-range radar out of Melbourne, Florida showed two of these bands about 75 - 150 miles east of the Central Florida coast. Sea surface temperatures in this region were about 1°C above average, 27 - 28°C--plenty of heat energy for a developing tropical cyclone. Wind shear was light, 5 - 10 knots, but was enough to keep any heavy thunderstorms from developing on the north side of 91L. Water vapor satellite loops showed some modest patches of dry air to the north of 91L, and this dry air was retarding development on Sunday morning. The Hurricane Hunters are on call to investigate 91L on Sunday afternoon.


Figure 1. MODIS satellite image of 91L, taken at approximately 18:30 UTC (2:30 pm EDT) on Sunday, June 29, 2014. Image credit: NASA.

Forecast for 91L
The 12Z Sunday run of the SHIPS model showed shear rising to the moderate range, 10 - 15 knots, beginning on Monday, and remaining moderate until the end of the week. There is a significant area of dry air to the north of 91L over North Carolina that may work its way south and get wrapped into its circulation on Monday and Tuesday, but this dry air should diminish on Wednesday. With the disturbance parked over the warm waters of the Gulf Stream, organization into a tropical depression is a good possibility. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave 91L 2-day and 5-day development odds of 40% and 70%, respectively. As of 11am EDT, the appearance of 91L on satellite images had improved to the point where I'd put the 2-day odds of development at 50%. Steering currents are weak off of the Southeast U.S. coast. The models all predict a slow southward drift on Sunday, followed by a southwesterly motion on Monday, which would bring the storm very close to the coast of Florida. The 06Z Sunday run of the GFS model has 91L making landfall over Florida on Tuesday, while the 00Z UKMET and European models stall the storm offshore, then accelerate it to the northeast later in the week, caught by a trough of low pressure to the north. Regardless of the exact track of 91L, the coast of Central Florida and the Northwest Bahamas are likely to receive heavy rains of at least 2 - 4" on Monday and Tuesday from 91L. If 91L develops into a tropical depression or tropical storm, widespread rainfall amounts of 4 - 8" will likely fall in coastal Central Florida and the Northwest Bahamas. Heavy rains are a potential threat for the coasts of Northern Florida, Georgia, South Carolina, and North Carolina late in the week, but there is high uncertainty in this possibility.

Jeff Masters

Hurricane

Updated: 1:42 AM GMT on June 30, 2014

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Disturbance 91L off Southeast U.S. Coast May Develop

By: JeffMasters, 3:39 PM GMT on June 28, 2014

A area of disturbed weather over the warm waters of the Gulf Stream current off the Southeast U.S. coast has been designated Invest 91L by NHC. Satellite loops on Saturday morning showed 91L with only a small amount of heavy thunderstorm activity that was poorly organized. There was no hint of a surface circulation trying to form. Long-range radar out of Melbourne, Florida showed a few modest areas of rainfall over the ocean about 50 - 150 miles east of the Central Florida coast. Sea surface temperatures in this region were about 1°C above average, 27 - 28°C--plenty of heat energy for a developing tropical cyclone. Wind shear was moderate, 10 - 15 knots. The shear was due to strong upper-level winds out of the north, which were keeping any heavy thunderstorms from developing on the north side of 91L. Water vapor satellite loops showed that the atmosphere was moderately moist off the Southeast U.S. coast, and dry air should not be a significant impediment to development. The Hurricane Hunters are on call to investigate 91L on Sunday afternoon.


Figure 1. Latest satellite image of 91L.

Forecast for 91L
The 12Z Saturday run of the SHIPS model showed light to moderate shear, 5 - 15 knots, over 91L for the next five days. With the disturbance parked over the warm waters of the Gulf Stream, organization into a tropical depression is a good possibility. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave 91L 2-day and 5-day development odds of 30% and 50%, respectively. As of noon EDT, I'd put these odds higher, at 40% and 60%, respectively. Steering currents are weak off of the Southeast U.S. coast, and the uncertainty in the track of 91L is higher than usual. The 00Z Saturday run of the UKMET and European models predicted a slow motion to the northeast, with the European model showing a potential threat to the North Carolina coast by Thursday. The 00Z and 06Z Saturday runs of the GFS model predict the opposite motion, a slow track southwestwards with a landfall in Florida on Tuesday. None of these models showed 91L reaching tropical storm strength. The UKMET and European model have been pretty consistent with their recent runs, so I favor their solution of a more northeasterly motion for 91L over the next five days.

I'll have an update on Sunday.

Jeff Masters

Hurricane

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Tropical Disturbance May Develop off Southeast U.S. Coast by Monday

By: JeffMasters, 2:55 PM GMT on June 27, 2014

A blow-up of thunderstorms over Texas and Louisiana on Wednesday created an area of low pressure that tracked east-northeast over the Southeast U.S., and was over Georgia and South Carolina on Friday. This low will emerge over the coastal South Carolina waters on Saturday, and move over the warm waters of the Gulf Stream current by Sunday. Sea surface temperature in this region are about 1°C above average, 27 - 28°C, which is plenty of heat energy for a developing tropical cyclone. Wind shear is moderate, 10 - 20 knots, and is forecast to remain moderate through Monday. These conditions favor development, though the 00Z Friday runs of our reliable tropical cyclone genesis models--the GFS, European, and UKMET--did not show development into a tropical depression. The disturbance will be in an area of weak steering currents, and the predominant track favored by the models is a slow south and then southwest movement towards Florida. The latest thinking from NOAA's Weather Prediction Center (Figure 1) is that the disturbance will bring a swath of 2 - 4" of rain from North Carolina to Florida during the coming week. These rainfall totals will be higher if the disturbance develops into a tropical depression. However, the system may not have much time over water before moving ashore over Florida on Monday, if the 00Z and 06Z Friday runs of the GFS model are correct. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odds of development of 0% and 20%, respectively.


Figure 1. Predicted precipitation for the 7-day period ending on Friday, July 4, 2014. A tropical disturbance off the Southeast U.S. coast is predicted to create a swath of 2 - 4 inches of rain from North Carolina to Florida. Image credit: NOAA's Weather Prediction Center.


Figure 2. There's nothing cooking off the coast of Africa: the tropical Atlantic was dominated by stable stratocumulus clouds and was free of heavy thunderstorm activity in this MODIS image taken on Friday morning, June 27, 2014. The murky appearance of this image is due to Saharan dust sweeping westwards off the coast of Africa. In the lee of the Cape Verde Islands, we can see beautiful Kármán vortex street clouds--a repeating pattern of swirling vortices caused by the unsteady separation of flow of air around the islands. The phenomenon is named after the engineer and fluid dynamicist Theodore von Kármán. Image credit: NASA.

Have a great weekend, everyone, and I'll have at least one update over the weekend.

Jeff Masters

Hurricane

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The Heat is on in Greenland: Support the Dark Snow Project

By: JeffMasters, 2:50 PM GMT on June 25, 2014

The heat is on in Greenland, where the high temperature on Tuesday hit an unusually warm 67°F at Kangerlussuaq (Sønder Strømfjord) in southwestern Greenland. It's been a hot June at Kangerlussuaq, where the temperature peaked at 73°F on June 15. That's not far below the all-time hottest temperature ever recorded in Greenland of 78.6°F, set just last year on July 30 at nearby Maniitsoq Mittarfia, as documented at wunderground's extremes page. The unusual warmth this year melted nearly 40% of the Greenland Ice Sheet in mid-June, according to data from the National Snow and Ice Data Center--far above the usual 15% figure. The warm June temperatures could be setting the stage for a big Greenland melt season this summer, and scientists with the Dark Snow Project are on the ice, 48 miles east Kangerlussuaq, conducting a two-month field experiment on the causes and implications of Greenland ice melt.


Video 1. Glaciologist Dr. Jason Box and climate change filmmaker Peter Sinclair explain the 2013 results and 2014 mission of the Darksnow project.

The Dark Snow Project
In 2013, glaciologist Dr. Jason Box of the Geological Survey of Denmark and Greenland launched the first crowd-funded Arctic expedition: The Dark Snow Project. The field study succeeded in its scientific mission of landing a team deep within the Greenland sheet, sampling the 2012 melt layer, and returning those samples for analysis. The results, soon to be published, showed a pronounced spike in black carbon at the critical layer, and indicated the strong need for more research. The "burning question": How much does wildfire and industrial soot darken the ice, increasing melt? Was the record melt and record darkness of the ice sheet in 2012 a harbinger of the future? A darker ice sheet absorbs more solar energy, in a vicious cycle that raises temperatures, melts more ice, and further darkens the ice sheet. The amount of melting that was caused by soot from forest fires is important to know, since global warming is likely to increase the amount of forest fires in coming decades. However, the amount of forest fire soot landing on the Greenland Ice Sheet is almost completely unknown.


Figure 1. Smoke from a fire in Labrador, Canada wafts over the Greenland ice sheet on June 17, 2012, as seen in this cross-section view of aerosol particles taken by NASA's CALIPSO satellite. Image credit: Dr. Jason Box, Ohio State University.

Saving Greenland's Ice Sheet is Imperative
Human-caused global warming has set in motion an unstoppable slow-motion collapse of the glaciers in West Antarctica capable of raising global sea level by 4 feet (1.2 meters) in a few hundred years, said NASA in a May 2014 press release. What's more, one of the glaciers involved, the Thwaites Glacier, acts as a linchpin on the rest of the ice sheet, which contains enough ice to cause a total of 10 to 13 feet (3 to 4 meters) of global sea level rise over a period of centuries. This unstoppable collapse makes saving Greenland "absolutely essential", said glaciologist Richard Alley in a May 2014 interview in Mother Jones. Greenland's ice sheet holds enough water to raise global sea levels by 7.36 meters (24.15 feet) were it all to melt, and civilization would be hard-pressed to deal with 10 - 13 feet of sea level rise from West Antarctica, let alone another 20+ feet from Greenland. "If we've committed to 3.3 meters (10.8') from West Antarctica, we haven't committed to losing Greenland, we haven't committed to losing most of East Antarctica," said Alley. "Those are still out there for us. And if anything, this new news just makes our decisions more important, and more powerful." Unfortunately, the Greenland Ice Sheet is much more vulnerable to melting than previously thought, found a May 2014 study by Morlighem et al., Deeply incised submarine glacial valleys beneath the Greenland ice sheet. The researchers found that widespread ice-covered valleys extend much deeper below sea level and farther inland than previously thought, and would likely melt significantly from steadily warming waters lapping at Greenland's shores.


Figure 2. Monthly changes in the total mass (in Gigatonnes) of the Greenland ice sheet estimated from GRACE satellite measurements between March 2002 - July 2013. The blue and orange asterisks denote April and July values, respectively. Note that the decline in ice mass lost from Greenland is not a straight line--it is exponential, meaning that in general, more ice loss is lost each year than in the previous year. However, the mass loss during the 2013 summer melt season was probably smaller than during 2012, said the 2013 Arctic Report Card.

Support for the Dark Snow Hypothesis
Observational evidence for the Dark Snow project's hypothesis that upwind forest fires might darken the Greenland Ice Sheet and cause significant melting was provided by a May 2014 paper by Keegan et al., Climate change and forest fires synergistically drive widespread melt events of the Greenland Ice Sheet. Their ice core study found that black carbon from forest fires helped caused a rare, near-ice-sheet-wide surface melt event that melted 97% of Greenland's surface on July 11 - 12 2012, and a similar event in 1889. Since Arctic temperatures and the frequency of forest fires are both expected to rise with climate change, the results suggest that widespread melt events on the Greenland Ice Sheet may begin to occur almost annually by the end of century.

Another factor contributing to a darker Greenland Ice Sheet and more melting may be additional wind-blown dust landing on the ice, according to a June 2014 study, Contribution of light-absorbing impurities in snow to Greenland's darkening since 2009. In an interview with ClimateWire, lead author Marie Dumont of France’s meteorological agency said, "Our hypothesis is that now that seasonal snow cover in the Arctic is retreating earlier than before, and bare soil is available earlier in the Spring for dust transport."

Related Jeff Masters blog posts
Slow-Motion Collapse of West Antarctic Glaciers is Unstoppable, 2 New Studies Say (May 13, 2014)
Dark Snow Project: Crowd-Source Funded Science for Greenland (April 26, 2013)
Greenland experiences melting over 97% of its area in mid-July (July 25, 2012)
Record warmth at the top of the Greenland Ice Sheet (July 18, 2012)
Unprecedented May heat in Greenland; update on 2011 Greenland ice melt (May, 2012)
Greenland update for 2010: record melting and a massive calving event

The http://www.greenlandmelting.com/ website has good resources for following this year's melt progression in Greenland.


Video 2. In a follow-up video, Dark Snow Project communications director Peter Sinclair explains how the recent finding of unstoppable West Antarctic glacial melt makes the saving of Greenland's glaciers absolutely essential.

Support the Dark Snow Project
One of Dr. Box's collaborators, photographer James Balog, who created the amazing time-lapse Greenland glacier footage in the fantastic 2012 "Chasing Ice" movie, puts it like this: "Working in Greenland these past years has left me with a profound feeling of being in the middle of a decisive historic moment--the kind of moment, at least in geologic terms, that marks the grand tidal changes of history." On that note, I encourage you all to consider a tax-deductible donation to the Dark Snow Project. The project has already raised $30,000, and hopes to raise another $10,000. One of the major uses for the money will be to pay for the portable Internet satellite gear needed to do regular posting, messaging, and skyping from the ice during July and August. The June 22 update from Dr. Box, as posted in Peter Sinclair's blog: "We saw a water fountain on the horizon, spouting to 100 feet above the surface. I think it is either a lot of water trying to fall down a small moulin cavitating, or a river on the ice sheet taking a violent turn. The spout lasted at least 18 hours!"

The tropics are still quiet and expected to remain so over the next five days, so I'll have a new post on Friday.

Jeff Masters

Glaciers Sea level rise Climate Change

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May 2014: Earth's 2nd Consecutive Warmest Month on Record

By: JeffMasters, 3:31 PM GMT on June 23, 2014

May 2014 was Earth's warmest May since records began in 1880, beating the record set in 2010, said NOAA's National Climatic Data Center (NCDC) and NASA. The planet has now had two back-to-back warmest months on record, since NOAA also rated April 2014 as being tied for the warmest April on record. This is the first time Earth has experienced back-to-back warmest months on record since a four-month stretch during March, April, May, and June 2010. Global ocean temperatures during May 2014 were 0.59°C (1.06°F) above the 20th century average; this ties with June 1998, October 2003, and July 2009 for the greatest departure from average of any month in recorded history. Global land temperatures were the 4th warmest on record in May 2014, and the year-to-date January - May period has been the 5th warmest on record for the globe. Global satellite-measured temperatures in May 2014 for the lowest 8 km of the atmosphere were 6th or 3rd warmest in the 36-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH), respectively. Northern Hemisphere snow cover during May was the 6th lowest in the 48-year record.


Figure 1. Departure of temperature from average for May 2014, the warmest May for the globe since record keeping began in 1880. In Europe, Latvia and Norway had their warmest May on record, as did South Korea in Asia. Portions of Central Asia and Australia were also record warm. No record cold was observed. Image credit: National Climatic Data Center (NCDC) .

Notable weather events of May 2014
According to wunderground's weather historian, Christopher C. Burt, in his May 2014 Global Weather Extremes Summary, an amazing heat wave occurred in China, Japan, and the Koreas the last week of May. Beijing saw its warmest May temperature on record with a 41.1°C (106.0°F) reading on May 30th, and all-time national heat records for the month of May were set for South Korea and China. A remarkable heat wave along the Baltic Sea broke the all time May heat record for Estonia (33.1°C/91.6°F at Kunda on May 19th) and at St. Petersburg, Russia with 33.0°C (91.4°F), also on May 19th. Gambia tied its all-time national heat record (for any month) on May 4th when the temperature rose to 45.5°C (113.9°F) at Kaur.


Figure 2. The deadliest weather disaster of 2014 so far has been the tragic landslide in the Argo District of Badakhshan Province, NE Afghanistan on May 2. Death toll estimates vary widely, from 350 - 2,700. According to Dave's Landslide Blog, the landslide came after prolonged heavy rainfall in the region and occurred in the middle of the day on a Friday, when many people are likely to be at home. The slide occurred in two phases, with an initial slide that buried many people. In the aftermath, many people from local villages went to help, only to be buried by the second landslide. Image credit: BBC correspondent Bilal Sarwary.



Three billion-dollar weather disasters in May 2014
Three billion-dollar weather-related disasters hit the Earth during May 2014, according to the May 2014 Catastrophe Report from insurance broker Aon Benfield. The total number of billion-dollar weather disasters through May is ten, which is behind the record-setting pace of 2013, which had thirteen such disasters by the end of May, and ended up with a record 41 such disasters by the end of the year.


Disaster 1. Torrential rains on May 14 - 15 in Serbia and Bosnia-Herzegovina caused extreme flooding that killed at least 80 people and caused $4.5 billion in damage. The heavy rains were caused by Extratropical Storm Yvette, a strong and slow-moving upper-level low pressure that cut off from the jet stream and lingered over the region for two days, pulling up copious amounts of moisture from the Mediterranean Sea. This aerial view of the flooded area near the Bosnian town of Brcko along the river Sava was taken May 18, 2014. (AP Photo/Bosnia Army)


Disaster 2. Flooding rains in China May 24 - 28 killed 37 people and caused $1.2 billion in damage. In this image we see dark clouds gathering in Guangzhou, Guangdong Province of China on May 22, 2014. Image credit: ChinaFotoPress/ChinaFotoPress via Getty Images.


Disaster 3. An outbreak of severe weather hit the Midwest, Rockies, and Northeast U.S. from May 18 - 23, causing $2.5 billion in damage. In this image taken by wunderphotographer Darhawk, we see a supercell thunderstorm near Denver, Colorado on May 22, 2014 that prompted issuance of a tornado warning.

An El Niño Watch continues
May 2014 featured neutral El Niño conditions in the equatorial Eastern Pacific, and sea surface temperatures have been hovering near the threshold for El Niño, +0.5°C from average, from late April through June 23. However, the atmosphere has not been behaving like it should during an El Niño event. The Southern Oscillation Index (SOI)--the difference in surface pressure between Darwin, Australia and the island of Tahiti--tends to drop to negative values during the presence of an El Niño atmosphere, but has been positive over the past 30 days. Heavy thunderstorm activity over Indonesia and near the International Date Line is typically enhanced during an El Niño event, and was near normal at the beginning of June. This activity has picked up over the past week, but must increase substantially before we can say the atmosphere is responding in an El Niño-like fashion. The Madden-Julian Oscillation, a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, is currently weak and disorganized, and will not be a factor in moving conditions towards El Niño this week. NOAA is continuing its El Niño Watch, giving a 70% chance that an El Niño event will occur by the summer, with an 80% chance by the fall. In a June 20 article at Climate Central, Stephen Baxter, a seasonal forecaster with NOAA's Climate Prediction Center, said: “we’re nicely on track for a weak to moderate, but still potentially impactful” El Niño event in the fall to winter months.

Arctic sea ice falls to 3rd lowest May extent on record
Arctic sea ice extent during May was the 3rd lowest in the 36-year satellite record, according to the National Snow and Ice Data Center (NSIDC).

Most impressive weather videos of May 2014


Video 1. One of the most spectacular weather videos taken in May 2014 was of a Low-Precipitation (LP) supercell thunderstorm on May 18, 2014, between Wright and Newcastle, WY. The best footage begins about 0:50 into the clip. The rotation of the thunderstorm is beautifully captured. LP supercells usually form in dry regions, where there might be just enough moisture to form the storm, but not enough moisture to rain very hard. You can usually find the updraft on the rear flank (back) of the storm. On radar, an LP will not show up as a hook echo because there's not enough precipitation within the storm to provide the reflectivity. These storms might not look that strong, but they can pack a punch. LP supercells often produce tornadoes and large hail.


Video 2. An EF-2 tornado with 120 mph winds hit this camp for oil workers just south of Watford City, North Dakota, on May 27, 2014. The tornado injured nine people and damaged or destroyed 15 trailers. Dan Yorgason, who lives in a neighboring workers camp to the one destroyed, filmed the tornado from inside his truck. "The tornado was coming down the hill along our only escape route. There was nowhere for us to go. It was crazy," he said. The contrast of the brown of the lower part of the funnel with the white portion of the upper funnel is particularly striking 2:00 into the video.


Video 3. A severed bridge floats down the Bosna River in Bosnia and Herzegovina on May 14, 2014. Here is a video of the bridge before it was swept away.

Win $100 in this month's wunderground "Climate Lottery"
Every three months, the Weather Channel's Guy Walton runs a "Climate Lottery" in his wunderground blog where players guess U.S. temperatures for the coming three months. Last season's winner earned a free 10-year wunderground membership. This winner of the new contest will pocket a cool $100. Simply go to Guy's blog and pick three numbers between 1 and 120 (with 1 representing the coldest possible ranking and 120 being the highest possible ranking) for June, July, and August 2014 U.S. temperatures, plus a tie-breaker “Power Ball” or overall ranking number for summer 2014. Post your prediction in the comments section of the blog. Picks must be made by midnight EDT July 5th. The National Climatic Data Center’s ranking numbers for summer 2014 will be posted on or shortly after September 15th, 2014.

I'll have a new post on Wednesday, as the tropics are quiet in the Atlantic, and no development is expected this week.

Jeff Masters

Climate Summaries

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Atlantic Hurricane Outlook for the Remainder of June

By: JeffMasters, 4:12 PM GMT on June 20, 2014

There were no tropical cyclones anywhere in the world on Friday, and none of the reliable models for forecasting tropical cyclone genesis in the Atlantic (European, GFS, and UKMET) is predicting development over the coming five days. There is a tropical disturbance off the east coast of Florida that radar out of Melbourne, Florida shows some spin to. However, satellite loops show the area of heavy thunderstorms is very limited, and there is a lot of dry air interfering with thunderstorm development. Wind shear is a moderate 10 knots. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave the disturbance 2-day and 5-day development odds of 10%. The disturbance will likely head northeast out to sea over the weekend.


Figure 1. Tropical disturbance off the east coast of Florida as seen at 11:15 am EDT June 20, 2014. Image credit: NASA/GSFC.

Hurricane Forecast for the Remainder of June
Vertical wind shear is predicted to be very high over most of the tropical Atlantic the remainder of June, reducing the odds of tropical storm formation. With the active thunderstorm area of the MJO predicted to remain over the Pacific Ocean the rest of June, this will favor dry, sinking air over the Atlantic, further discouraging tropical storms from forming. Sea surface temperatures (SSTs), which are close to average over the Caribbean (an anomaly of +0.1°F) and cooler than average over the Gulf of Mexico (an anomaly of -0.2°F) will do no favors for any potential June tropical storms that try to form. If development does occur in June, the most likely location would be off the east coast of Florida, between the Bahamas and Bermuda, where SSTs are slightly above average and wind shear will be lower. Storms that form in this region are typically only a threat to Bermuda.

Since the active hurricane period we are in began in 1995, six of the nineteen years (32%) did not have a named storm develop in June. I give an 80% chance that 2014 will join that list. The most recent year without a June named storm developing was the El Niño year of 2009. The highest number of named storms for the month is three, which occurred in 1936 and 1968. There were two June named storms in 2013, Andrea and Barry.


Figure 2. Predicted vertical wind shear between the 850 mb and 200 mb levels for 8 am EDT Friday, June 27, 2014, as predicted by the 00Z Friday, June 20, 2014 run of the European model. High wind shear is predicted for most of the tropical Atlantic, thanks to the presence of strong upper-level winds from the subtropical jet stream (marked with arrows.) Low wind shear (red colors) are predicted for the waters of the Bahama Islands and in the Eastern Pacific off the coast of Mexico.


Figure 3. Vertical instability over the tropical Atlantic in 2014 (blue line) compared to average (black line.) The instability is plotted in °C, as a difference in temperature from near the surface to the upper atmosphere. Thunderstorms grow much more readily when vertical instability is high. Instability was been much lower than average during June, primarily due to dry, sinking air from aloft and outbreaks of dry air from Africa's Saharan Air Layer (SAL). Low instability reduces the potential for tropical storm formation. Image credit: NOAA/NESDIS/CIRA.

Have a great weekend, everyone!

Jeff Masters

Hurricane

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Drought in Syria: a Major Cause of the Civil War?

By: JeffMasters, 12:54 PM GMT on June 18, 2014

Syria's devastating civil war that began in March 2011 has killed over 200,000 people, displaced at least 4.5 million, and created 3 million refugees. While the causes of the war are complex, a key contributing factor was the nation's devastating 2006 - 2011 drought, one of the worst in the nation's history, according to new research accepted for publication in the journal Weather, Climate, and Society by water resources expert Dr. Peter Gleick of the Pacific Institute. The drought brought the Fertile Crescent's lowest 4-year rainfall amounts since 1940, and Syria's most severe set of crop failures in recorded history. The worst drought-affected regions were eastern Syria, northern Iraq, and Iran, the major grain-growing areas of the northern Fertile Crescent. In a press release that accompanied the release of the new paper, Dr. Gleick said that as a result of the drought, "the decrease in water availability, water mismanagement, agricultural failures, and related economic deterioration contributed to population dislocations and the migration of rural communities to nearby cities. These factors further contributed to urban unemployment, economic dislocations, food insecurity for more than a million people, and subsequent social unrest."


Figure 1. The highest level of drought, "Exceptional", was affecting much of Western Syria in April 2014, as measured by the one-year Standardized Precipitation Index (SPI). Image credit: NOAA's Global Drought Portal.

Human-caused climate change a major factor in more frequent Mediterranean droughts
The paper also assessed the role of climatic change in altering water availability. There is growing evidence that annual and seasonal drought frequency and intensity in the Levant/Eastern Mediterranean region have increased from historical climatic norms, with the number of dry days increasing during the winter rainy season. Similar findings were discussed in a NOAA press release that accompanied the release of a 2011 paper by Hoerling et al., "On the Increased Frequency of Mediterranean Drought." That paper found that human-caused emissions greenhouse gases were "a key attributable factor" in the drying up of wintertime precipitation in the Mediterranean region in recent decades.


Figure 2. Winter precipitation trends in the Mediterranean region for the period 1902 - 2010. In the 20 years ending in 2010, 10 of the driest 12 winters took place in the lands surrounding the Mediterranean Sea. Image credit: NOAA.

Future conflict over water in the Middle East
The potential for future conflict in the Middle East over water is significant. Researchers Heidi Cullen and Peter deMenocal discussed previous incidents in 1975 and 1990: Turkey, because it has the good fortune of being situated at the headwaters of the Tigris – Euphrates River system, can literally turn off the water supply of its downstream neighbors. When the Ataturk Dam was completed in 1990, Turkey stopped the flow of the Euphrates entirely for 1 month, leaving Iraq and Syria in considerable distress. Similarly, in 1975, when the Syrians began filling Lake Assad after completion of work on the Tabqa Dam, Iraq threatened to bomb the dam, alleging that it seriously reduced the river’s flow. Both countries amassed troops along the border.


Figure 3. Stele of Narâm-Sîn, king of the Akkadian Empire, celebrating his victory against the Lullubi from Zagros. Limestone, c. 2250 BCE, Louvre Museum. Image credit: Marie-Lan Nguyen

A great Syrian drought 4,200 years ago
Great civilization-threatening droughts have happened before in Syria. In a 2000 article published in Geology, "Climate change and the collapse of the Akkadian empire: Evidence from the deep sea", a team of researchers led by Heidi Cullen studied deposits of continental dust blown into the Gulf of Oman in the late 1990s. They discovered a large increase in dust 4,200 years ago that likely coincided with a 100-year drought that brought a 30% decline in precipitation to Syria. The drought, called the 4.2 kiloyear event, is thought to have been caused by cooler sea surface temperatures in the North Atlantic. The Akkadian Empire, which flourished in ancient Mesopotamia between 2334 BC - 2193 BC, also crashed at this time, giving credence to the idea that the drought may have been a key reason why. The 4.2 kiloyear event has also been linked to the collapse of the Old Kingdom in Egypt. The paper concluded, "Geochemical correlation of volcanic ash shards between the archeological site and marine sediment record establishes a direct temporal link between Mesopotamian aridification and social collapse, implicating a sudden shift to more arid conditions as a key factor contributing to the collapse of the Akkadian empire."

Commentary
People fear storms, and spectacular and devastating storms like Hurricane Sandy and Hurricane Katrina have stirred more debate in the U.S. about taking action against climate change than any other weather events. But I argue that the on-going Western U.S. mega-drought and Syrian drought should be louder wake-up calls. Drought is the greatest threat civilization faces from climate change, because drought takes away the two things necessary to sustain life--food and water. Drought experts Justin Sheffield and Eric Wood of Princeton, in their 2011 book, Drought, list more than ten civilizations and cultures that probably collapsed, in part, because of drought. Among them: The Mayans of 800 - 1000 AD. The Anasazi culture in the Southwest U.S. in the 11th - 12th centuries. The ancient Akkadian Empire in Mesopotamia. The Chinese Ming Dynasty of 1500 - 1730. When the rains stop and the soil dries up, cities die and civilizations collapse, as people abandon lands no longer able to supply them with the food and water they need to live. The fact that the most politically volatile region on the planet is already experiencing an increase in drought that research links to climate change should be a serious wake-up call about the need to manage water resources more wisely--and to work to forge an international agreement in Paris in 2015 to cut down on the amount of heat-trapping carbon dioxide humans are putting into the air. Dr. Gleick's paper concludes with sensible options for reducing the risks of water-related conflicts in the Middle East, including expansion of efficient irrigation technologies and practices, integrated management and monitoring of groundwater resources, and diplomatic and political efforts to improve the joint management of shared international watersheds and rivers.

References
Gleick, P., 2014, Water, Drought, Climate Change, and Conflict in Syria, accepted for publication in Weather, Climate, and Society

Cullen, H.M., and P.B. deMenocal, 2000, North Atlantic Influence on TIgris-Euphrates Streamflow, International Journal of Climatology, 20: 853-863.

Hoerling, Martin, Jon Eischeid, Judith Perlwitz, Xiaowei Quan, Tao Zhang, Philip Pegion, 2012, On the Increased Frequency of Mediterranean Drought, J. Climate, 25, 2146–2161, doi: http://dx.doi.org/10.1175/JCLI-D-11-00296.1

Kaniewski, D. et al., 2012, Drought is a recurring challenge in the Middle East, PNAS 109:10, 3862–3867, doi: 10.1073/pnas.1116304109

I'll have a new post on Friday.

Jeff Masters

Drought Climate Change

Updated: 1:17 PM GMT on June 18, 2014

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Rare Twin Tornadoes Kill Two in Nebraska

By: JeffMasters, 2:27 PM GMT on June 17, 2014

Rare twin tornadoes plowed through the small town of Pilger (population 380) in northeastern Nebraska Monday night, killing at least two people. According to the National Weather Service in Omaha, these were the first tornado deaths in Nebraska in over ten years, since the May 22, 2004 Hallam, Nebraska tornado. Yesterday's unusual twin tornadoes were part of a tornado outbreak that brought nineteen tornadoes to Nebraska and Iowa that injured at least nineteen people. According to Sheriff Mike Unger of the Stanton County Sheriff's office, 75% of Pilger was destroyed, including 100% of the business district. The church, school, and fire department buildings were demolished. NWS damage survey results from Tuesday showed several spots of EF-4 damage in Pilger.


Figure 1. Picture from Reed TImmer (@reedtimmerTVN) of twin tornadoes and severe damage near Pilger, NE #newx on June 16, 2014.


Figure 2. The twin tornadoes that devastated Pilger, NE on June 16, 2014. Image credit: Greg Johnson.


Figure 3. Radar reflectivity image of the powerful isolated supercell thunderstorm that hit Pilger, Nebraska on June 16, 2014.


Figure 4. Doppler velocity image of the Pilger, Nebraska supercell thunderstorm on June 16, 2014. Two separate areas of spin are apparent on the radar, with winds blowing towards the radar and away. Pilger is marked by the circle with a "+" in it.


Video 1. Rare twin tornadoes near Pilger and Wisner, Nebraska as caught by iowachase.com (AKA ‪‪StormChasingVideo‬‬.com.)


Video 2. Rare twin tornadoes near Pilger and Wisner, Nebraska as caught by BaseHuntersChasing


Video 3. Aerial damage survey from a Nebraska State Patrol helicopter shows the damage swath through Pilger, Nebraska, on June 16, 2014. Damage was as high as EF-4.


Twin tornadoes are rare
While it is common for large, violent tornadoes to form multiple funnels that rotate around each other, Monday night's Pilger, Nebraska twin tornadoes were not one of these standard "multi-vortex" entities. The Pilger tornadoes were separated by 2 - 3 miles, and were both spawned by the same isolated supercell thunderstorm. A rotating supercell thunderstorm typically has just one center of rotation and spawns only one tornado, but Monday's storm was so massive that it was able to form two centers of rotation that each spawned large and destructive tornadoes. Video taken by iowachase.com shows a large tornado hurling debris into the air near the 3:31 mark, and by 3:32 a second tornado touches down 2 - 3 miles away. Within minutes, the 2nd tornado grows very large and puts a substantial amount of debris into the air.


Figure 5. The most famous case of twin tornadoes occurred on April 11, 1965, during the notorious Palm Sunday Tornado Outbreak. These twin tornadoes that hit Elkhart County, Indiana caused F-4 damage and killed 14 people. Just 45 minutes later, a second F-4 double funnel hit just two-and-a-half miles away, killing 36 people. The twin tornadoes in this image were probably not two separate tornadoes, but rather one multi-vortex tornado with two impressively large funnels. Here is a paper by Fujita et al. on the 1965 Palm Sunday outbreak, including a detailed analysis of the twin tornadoes in the photograph: http://docs.lib.noaa.gov/rescue/mwr/098/mwr-098-01-0029.pdf. Unlike the Pilger twin tornadoes, the 1965 twin was a single tornado which broke down into two circulations. Image credit: Paul Huffman.

Thanks go to wunderground members Sfloridacat5, Ameister12, Doppler22 and barbamz for posting some of the links used in this post.

Jeff Masters

Tornado

Updated: 7:10 PM GMT on June 17, 2014

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No Tropical Storm Formation Expected in the Atlantic This Week

By: JeffMasters, 2:49 PM GMT on June 16, 2014

There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. The operational GFS model, which had been predicting all of last week that a strong tropical disturbance or tropical storm would develop over the Western Caribbean late this week, has now backed off on that forecast, though a few members of the GFS ensemble forecast are still predicting development in the Southwest Caribbean late this week. As I explained in Friday's blog post, the GFS model's forecasts of tropical development occurring in the Western Caribbean are likely bogus. Vertical wind shear will be very high over most of the tropical Atlantic this week, and there will be a large amount of dry, sinking air, making it difficult for tropical storms to form. It's a different story in the Eastern Pacific, where low wind shear and moist conditions may lead to the formation of a new tropical depression late in the week. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave a 30% chance that a tropical depression could form by Saturday, a few hundred miles south of Mexico's Pacific coast. This morning's 00Z run of the European model supports formation of a tropical depression late this week in the Eastern Pacific.


Figure 1. Predicted vertical wind shear between the 850 mb and 200 mb levels for 8 am EDT Friday, June 20, 2014, as predicted by the 00Z Monday, June 16, 2014 run of the European model. High wind shear is predicted for most of the tropical Atlantic, thanks to the presence of strong upper-level winds from the subtropical jet stream. The region marked "Low Shear" in the Eastern Pacific has been given a 30% chance of spawning a tropical depression by Saturday in NHC's 8 am EDT Monday Tropical Weather Outlook.

Jeff Masters

Hurricane

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Bogus GFS Model Forecasts of Atlantic Tropical Cyclone Genesis

By: JeffMasters, 3:49 PM GMT on June 13, 2014

There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. However, the 00Z Friday run of the GFS model predicts that a low pressure area will develop over the Western Caribbean by Wednesday, and push northwards into the Gulf of Mexico and become a tropical storm late in the week. The GFS has been fixated on variations of this idea in all of its runs for the past five days--though the timing of when the predicted storm will form has bounced around from 5 - 11 days into the future. Should we be concerned? A 2013 study by a group of scientists led by Florida State's Daniel Halperin found that we have three models that can make decent forecasts of the genesis of new tropical cyclones in the Atlantic: the GFS, European (ECMWF), and UKMET models. The study only evaluated the model skill for forecasts out to four days in the future, and the forecast skill declined markedly for three- and four-day forecasts. In the current scenario, we are talking about forecasts made much further into the future, which are bound to be low-skill. In addition, the study found that the GFS model had a high incidence of false alarms for tropical cyclone genesis forecasts in the Caribbean (50%). The other two reliable models for predicting tropical cyclone genesis (European and UKMET) had no hint of a low pressure area developing in the Western Caribbean on Wednesday in their 00Z Friday runs. One additional model to consider: the 00Z Friday run of the NAVGEM model is supporting the GFS's idea of a low pressure area forming in the Western Caribbean by Wednesday. The predecessor to this model, the NOGAPS model, was evaluated in the Florida State study, but performed poorly in making tropical cyclone genesis forecasts. However, when two or more models make the same genesis forecast, the odds of the event actually occurring are increased considerably, the study found.


Figure 1. Friday the 13th, GFS style: The 00Z UTC Friday, June 13, 2014 forecast from the GFS model for nine days into the future shows a powerful tropical storm in the Gulf of Mexico. The purple colors indicate winds of 50 - 60 knots (57 - 69 mph.) But is it a bogus forecast? Very likely.


Figure 2. The 2004–11 GFS forecasts for tropical cyclone genesis, showing Hits (green triangle), False Alarms (red square), and Incorrect Timing (blue circle) event locations. Numbers in parentheses are the numbers of model-predicted events. The model made 46 forecasts that a tropical depression or tropical storm would form in the Caribbean (purple box) during this 8-year period. Fully 50% of these forecasts were False Alarms; 11% of the forecasts verified, but the timing was off by at least a day (IT events); and 39% of the genesis forecasts verified with the right timing. Noteworthy is the model's few False Alarms over the Gulf of Mexico: only 15% of the total. Image credit: Halperin et al., 2013, Weather and Forecasting, "An evaluation of tropical cyclone genesis forecasts from global numerical models."

We know that the GFS model gets in trouble when making predictions of heavy thunderstorm activity via a problem called "convective feedback." Basically, the model sometimes simulates that an unrealistically large area of thunderstorms will develop, destabilize the atmosphere, and cause an area of low pressure to form that will draw in more moisture and create more heavy thunderstorms. This vicious cycle can snowball out of control and generate a bogus low pressure area that can then modify the upper level winds, reduce the wind shear, and allow a tropical depression to form. This problem may be less of an issue in a new version of the GFS model scheduled to be released late this summer; NHC hurricane specialist Eric Blake tweeted on Tuesday a comparison of the old and new 1-week GFS model forecasts for the Western Caribbean made last Tuesday, showing that the upgraded GFS model was not creating nearly as strong of a low pressure system as the old GFS model. Arguing against any development in the Atlantic the remainder of June is the anticipated strengthening in the West-Central Pacific Ocean of the Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days. An active MJO in that part of the tropics tends to bring large-scale sinking motion to the tropical Atlantic and increased wind shear, which puts a damper on the chances of tropical storm formation in the Atlantic. The MJO is predicted to drift slowly eastwards into the Eastern Pacific by late June, which will tend to keep odds of tropical storm formation lower than average in the Atlantic into late June. All factors considered, I am inclined to give a 10% chance that the GFS model is correct in spinning up a tropical depression late in the week in the Western Caribbean.

Hurricane Cristina weakening
Hurricane Cristina is headed downhill after peaking as powerful Category 4 hurricane with 150 mph winds and a central pressure estimated at 935 mb at 11 am EDT Thursday, June 12, 2014. The double feature of Category 4 hurricanes Cristina and Amanda gives 2014 two of the five strongest hurricanes ever recorded in the Eastern Pacific so early in the year:

Top Five Strongest Early Season (May - June) Eastern Pacific Hurricanes
1973, June 6: Hurricane Ava, 160 mph, 915 mb.
2010, June 25: Hurricane Celia, 160 mph, 921 mb
2014, May 25: Hurricane Amanda, 155 mph, 932 mb
2000, June 21: Hurricane Carlotta, 155 mph, 932 mb
2014, June 12: Hurricane Cristina, 150 mph, 935 mb


Figure 3. True-color MODIS image from the Aqua satellite of Hurricane Cristina at 18 UTC Thursday, June 12, 2014. At the time, Cristina was a Category 4 storm with 145 mph winds. Image credit: NASA.

Arabian Sea's Tropical Cyclone Nanauk dissipates
Tropical Cyclone Nanauk in the Arabian Sea has been torn apart by high wind shear of 25 - 30 knots and dry air, and is no longer a threat to Oman.

Have a great weekend, everyone!

Jeff Masters

Hurricane

Updated: 4:04 PM GMT on June 13, 2014

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Hurricane Cristina Hits Cat 4; Little Change to Arabian Sea Tropical Cyclone Nanauk

By: JeffMasters, 3:02 PM GMT on June 12, 2014

Hurricane Cristina walled off the dry air surrounding it and put on an impressive round of rapid intensification overnight, topping out as powerful Category 4 hurricane with 150 mph winds and a central pressure estimated at 935 mb at 11 am EDT Thursday. Cristina is the second hurricane this year to reach major hurricane strength in the Eastern Pacific, setting a record for the earliest date of formation for the season's second major hurricane. The previous record was a full thirteen days later in the season: June 25, 2010, when Hurricane Darby reached Category 3 strength. The other major hurricane this year in the Eastern Pacific was Hurricane Amanda, which peaked as a top-end Category 4 hurricane with 155 mph winds at 15 UTC (10 am EST) May 25, becoming the strongest May hurricane ever recorded in the Eastern Pacific. This year is also the first time there have been two Category 4 hurricanes before July 1 in the Eastern Pacific. Prior to Cristina, the earliest second Category 4 hurricane was Hurricane Elida in 1984, which reached that threshold on July 1. Reliable records for the basin go back to 1966.


Figure 1. Cristina near peak strength at 12:16 pm EDT June 12, 2014.

The usual formation date for the second hurricane of the Eastern Pacific season is July 14, so we are over a month ahead of usual for hurricanes in 2014. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes, so we've already had half the usual number of major hurricanes for an entire season, with the typical August 24 peak of the season nearly two and a half months away. This year is shaping up to be an El Niño year, and El Niño conditions typically increase the sea surface temperatures and decrease the vertical wind shear over the tropical Eastern Pacific, favoring the development of more and stronger tropical cyclones.


Figure 2. True-color MODIS image from the Aqua satellite of Hurricane Cristina at 21 UTC Wednesday, June 11, 2014. At the time, Cristina was a Category 1 storm with 80 mph winds. Image credit: NASA.

Satellite loops show that Cristina has an impressive eye surrounded by an eyewall with very cold cloud tops. The eyewall is thinner on the northwest side of the eye, suggesting that wind shear of about 5 - 10 knots due to upper level winds out of the northwest is affecting the storm. There is still time for Cristina to potentially intensify into a Category 5 storm today, but increasing wind shear combined with decreasing sea surface temperatures will begin to weaken the storm on Friday and into the weekend. Cristina is headed away from Mexico, and no watches or warnings will be required.

Little change to Arabian Sea's Tropical Cyclone Nanauk
Tropical Cyclone Nanauk continues steaming westwards across the Arabian Sea at 11 mph towards Oman. Nanauk is over some of the warmest ocean waters on the planet, 31 - 32°C (88 - 90°F), but has changed little in strength over the past two days, due to high wind shear of 25 - 30 knots, which is disrupting the circulation. Nanauk is expected to continue moving west-northwest towards Oman Thursday, but both the European and GFS models now predict that Nanauk will dissipate in the next two days. High wind shear associated with the advancing Southwest Monsoon is predicted to increase over Nanauk, allowing very dry air over the Middle East to penetrate deep into the storm's core and disrupt it. This would be very good news for Oman, which has suffered a number of deadly and costly tropical cyclone landfalls since 2002.


Figure 3. True-color MODIS image from the Aqua satellite of Tropical Cyclone Nanauk (65 mph sustained winds) over the Arabian Sea taken at approximately 6:30 am EDT June 12, 2014. The coast of Oman can be seen at the left side of the image. Image credit: NASA.

Tropical cyclones rare in Oman
Tropical cyclones are quite rare in Oman, but have hit the nation unusually often in the past few years. According to NOAA's Historical Hurricane Tracks database, only five have hit Oman at tropical storm strength or higher since accurate satellite data began in 1990, with three of those landfalls occurring since 2007:

Nov. 2, 2011: 40 mph tropical storm, Keila (14 killed)
June 4, 2010: 75 mph Category 1 hurricane, Tropical Cyclone Phet (24 killed)
June 6, 2007: 75 mph Category 1 hurricane, Tropical Cyclone Gonu (50 killed)
May 10, 2002: 40 mph tropical storm, the 2002 Oman cyclone (9 killed)
October 3, 1992: 45 mph tropical storm

Earlier historical landfall records indicated that the deadliest cyclone to affect Oman was a Category 1 storm that hit on June 13, 1977, killing 105 people.

Tropical Cyclones Gonu of 2007: Oman's Costliest Natural Disaster
The most expensive natural disaster in Oman's history was Tropical Cyclone Gonu, which hit the eastern tip of Oman as a Category 1 storm on June 6, 2007. Gonu is the first Category 4 or higher storm recorded in the Arabian Sea since the satellite era began in 1970. The Joint Typhoon Warning Center (JTWC) estimated Gonu's peak sustained winds at 165 mph, the strongest winds of any tropical cyclone they have ever rated in the northern Indian Ocean (second place: the 160 mph winds of the 1991 Bangladesh cyclone that killed 138,000 people.) Fortunately, dry air and wind shear knocked Gonu down to Category 1 strength before landfall, but the storm still killed 50 people and did $4.2 billion in damage (2007 USD) in Oman, with flash flooding causing most of the deaths and destruction. Gonu dropped heavy rainfall of up to 610 mm (24 inches) on Oman's east coast, which is six times higher than the annual rainfall in Oman of 100 mm (about 4".) In Iran, the cyclone caused 28 deaths and $216 million in damage (2007 USD).


Video 1. The Story About Cyclone Gonu video shows remarkable footage of why so many people died in Oman: they went out into the flood waters in their cars.

Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. The GFS model continues to predict that about 6 - 9 days from now the upper level winds over the Western Caribbean will relax and low-level moisture will build, potentially allowing a tropical disturbance with heavy rains to develop there. However, the European model keeps the wind shear high over the Western Caribbean early next week, so any development in the region remains in doubt.

Jeff Masters

Hurricane

Updated: 4:36 PM GMT on June 12, 2014

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Tropical Cyclone Nanauk a threat to Oman; Hurricane Cristina Forms in Eastern Pacific

By: JeffMasters, 3:16 PM GMT on June 11, 2014

Oman is nervously watching Tropical Cyclone Nanauk (also called Tropical Cyclone Two), a tropical storm with 65 mph winds that is moving west-northwest at 6 mph across the Arabian Sea. Nanauk is over some of the warmest ocean waters on the planet, 31 - 32°C (88 - 90°F). Very warm waters extend to great depth beneath the storm, giving it a Tropical Cyclone Heat Potential (TCHP) of 80 - 120 kJ/cm^2, the type of heat energy that is often associated with rapid intensification. However, Nanauk lies at the southern edge of a large area of dry air coming off the deserts of the Middle East, which is interfering with development. In addition, Nanauk is on the northern edge of the advancing Southwest Monsoon, and strong upper-level winds out of the east associated with the monsoon are bringing high wind shear of 20 - 25 knots, disrupting the circulation.


Figure 1. Morning satellite image of Tropical Cyclone Nanauk over the Arabian Sea.

Forecast for Nanauk
Nanauk is expected to continue moving west-northwest towards Oman the remainder of the week, which will bring the storm into an area with dryer air but lower wind shear. It is difficult to predict how these two competing influences might affect the storm. As a result, the track and intensity forecasts are very divergent. The European model dissipates Nanauk by Wednesday, while the GFS model keeps the storm strong, until weakening occurs shortly before landfall in Oman near 21 UTC on Saturday. Given the storm's ability to fight off high wind shear thus far, I am inclined to go with the GFS forecast of a weakening tropical storm at landfall. Tropical cyclones typically weaken rapidly as they approach the coast of Oman, due to very dry air over the Middle East getting sucked into their circulation.


Figure 2. Progress of the Southwest Monsoon in India in 2014 (blue line and white lines), compared to average (red dashed lines.) The monsoon is running about 4 - 11 days behind schedule, which has allowed Tropical Cyclone Nanauk room to form in the Arabian Sea. Image credit: India Meteorological Department.

The Monsoon and India
The North Indian Ocean has two tropical cyclone seasons--one in May and June before the Southwest Monsoon arrives, and one in October - November after the Monsoon has departed. Ordinary tropical cyclones typically do not form during the monsoon, but huge "monsoon depressions" that fill nearly the entire Bay of Bengal with sustained winds of 30 - 35 mph occasionally form during the monsoon. Nanauk formed just at the leading edge of the advancing monsoon, which is running 4 -11 days behind this year. Nanauk is sapping much of the energy of the monsoon today, which is much less active than it was early in the week. The monsoon is vital to the well-being of India, since the farm sector accounts for 14% of India's nearly $2 trillion economy, and half of India's farmland lacks access to irrigation. The likely development of El Niño this year is of concern for agriculture in India, since El Niño tends to cut down on the monsoon's rains. All of India's great famines since the late 1800s have come in years when the monsoon rains failed during El Niño events.

Record heat scorching India and Nepal
India, Nepal, Pakistan, and Bangladesh typically experience their hottest weather in May and June, just before the arrival of the cooling rains of the monsoon. As reported by wunderground's weather historian Christopher C. Burt in his latest blog post, India has seen extreme heat for the past week, which has led to electricty shortages and riots. At New Delhi’s Palam Airport, the temperature reached 47.8°C (118.0°F) on June 8th, their 2nd hottest temperature ever measured. Agra hit a blistering 47.3° (117.1°F) on June 10th, and 48.6°C (119.5°F) was reported from Ganganagar on June 8th, the warmest reading so far in the country in 2014. In Nepal, the temperature peaked at 45.2°C (113.4°F) at Dipayal, just short of the all-time national record for any month of 46.4°C (115.5°F) set at Dhanghadi on June 16, 1995. Europe has also seen record-breaking June temperatures this week, with Germany hitting its second highest temperature ever recorded in June, 37.9°C (100.2°F) on June 9th in Ihringen.

Cristina becomes a hurricane in the Eastern Pacific
The Eastern Pacific's second hurricane of 2014 is here, as Hurricane Cristina intensified overnight into a Category 1 storm with 75 mph winds. Satellite loops show that Cristina has ingested some dry air and has now leveled off in intensity. Cristina is headed away from Mexico, and it is unlikely that any watches or warnings will be required for this storm.

The usual formation date for the second hurricane of the Eastern Pacific season is July 14, so we are over a month ahead of usual for hurricanes in 2014. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes. NOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 22, is calling for an active season, with around 17 named storms, 9 hurricanes, and 4.5 major hurricanes. This year is shaping up to be an El Niño year, and El Niño conditions typically increase the sea surface temperatures and decrease the vertical wind shear over the tropical Eastern Pacific, favoring the development of more and stronger tropical cyclones.


Figure 3. Latest satellite image of Cristina off the Pacific coast of Mexico.

Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. The GFS model continues to predict that about 6 - 9 days from now the upper level winds over the Western Caribbean will relax and low-level moisture will build, potentially allowing a tropical disturbance with heavy rains to develop there. However, the European model keeps the wind shear high over the Western Caribbean early next week, so any development in the region remains in doubt.

Jeff Masters

Hurricane

Updated: 6:03 PM GMT on June 11, 2014

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Eastern Pacific's Cristina no Threat to Land; Arabian Sea's TC 2 a Threat to Oman

By: JeffMasters, 3:21 PM GMT on June 10, 2014

The Eastern Pacific's third named storm of 2014 is here, as Tropical Storm Cristina spun into life late Monday night about 150 miles south of Mexico's Pacific coast. Satellite loops show that Cristina is still in the formative stages, but the combination of low wind shear and water temperatures that are a very warm 30°C (about 0.5°C above average) should allow Cristina to intensify into a Category 1 hurricane later this week. Cristina is headed away from Mexico, and it is unlikely that any watches or warnings will be required for this storm.

The formation of the Eastern Pacific's third storm of the season on June 10 comes nearly a month before the climatological average of July 5 for the usual appearance of the third storm. We've already had one hurricane in the Eastern Pacific this year (Category 4 Amanda, the strongest May hurricane ever observed in the Eastern Pacific), and the usual formation date for the second hurricane of the season is July 14. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes. NOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 22, is calling for an active season, with around 17 named storms, 9 hurricanes, and 4.5 major hurricanes. This year is shaping up to be an El Niño year, and El Niño conditions typically increase the sea surface temperatures and decrease the vertical wind shear over the tropical Eastern Pacific, favoring the development of more and stronger tropical cyclones.


Figure 1. Latest satellite image of Cristina off the Pacific coast of Mexico.

Tropical Cyclone Two a threat to Oman
The North Indian Ocean has some activity today in the form of Tropical Cyclone Two, a tropical storm with 45 mph winds that has formed in the Arabian Sea. Tropical Cyclone Two is expected to head west-northwest toward Oman and intensify into a Category 1 storm later this week, though the intensity forecast is a difficult one, due to moderate wind shear of 15 - 20 knots and the presence of dry air. The North Indian Ocean has two tropical cyclone seasons--one in May and June before the Southwest Monsoon arrives, and one in October - November after the Monsoon has departed.


Figure 2. True-color MODIS image from the Terra satellite of Tropical Cyclone Two over the Arabian Sea taken at approximately 6:30 am EDT June 10, 2014. The storm appears to be pulling in a plume of dust or pollution from the north, flowing off the coast of India (some sunglint reflecting off the water is making it difficult to tell for sure.) The coast of Oman can be seen at the left side of the image. Image credit: NASA.

Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. Strong upper-level winds, associated with the subtropical jet stream, are bringing high levels of wind shear over the tropical Atlantic and Gulf of Mexico, and these high winds are forecast to persist for at least the next six days. The GFS model continues to predict that about 7 - 10 days from now the upper level winds over the Western Caribbean will relax and low-level moisture will build, potentially allowing a tropical disturbance with heavy rains to develop there. However, the European model keeps the wind shear high over the Western Caribbean early next week, so any development in the region remains in doubt. Arguing against any development in the Atlantic is the anticipated strengthening next week in the West-Central Pacific Ocean of the Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days. An active MJO in that part of the tropics tends to bring large-scale sinking motion to the tropical Atlantic and increased wind shear, which puts a damper on the chances of tropical storm formation in the Atlantic. The MJO is predicted to drift slowly eastwards into the Eastern Pacific by late June, which will tend to keep odds of tropical storm formation lower than average in the Atlantic into late June.

Jeff Masters

Hurricane

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Cristina in Eastern Pacific no Threat to Land; TC 2 in Arabian Sea a Threat to Oman

By: JeffMasters, 3:16 PM GMT on June 10, 2014

The Eastern Pacific's third named storm of 2014 is here, as Tropical Storm Cristina spun into life late Monday night about 150 miles south of Mexico's Pacific coast. Satellite loops show that Cristina is still in the formative stages, but the combination of low wind shear and water temperatures that are a very warm 30°C (about 0.5°C above average) should allow Cristina to intensify into a Category 1 hurricane later this week. Cristina is headed away from Mexico, and it is unlikely that any watches or warnings will be required for this storm.

The formation of the Eastern Pacific's third storm of the season on June 10 comes nearly a month before the climatological average of July 5 for the usual appearance of the third storm. We've already had one hurricane in the Eastern Pacific this year (Category 4 Amanda, the strongest May hurricane ever observed in the Eastern Pacific), and the usual formation date for the second hurricane of the season is July 14. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes. NOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 22, is calling for an active season, with around 17 named storms, 9 hurricanes, and 4.5 major hurricanes. This year is shaping up to be an El Niño year, and El Niño conditions typically increase the seas surface temperatures and decrease the vertical wind shear over the tropical Eastern Pacific, favoring the development of more and stronger tropical cyclones.


Figure 1. Latest satellite image of Cristina off the Pacific coast of Mexico.

Tropical Cyclone Two a threat to Oman
The North Indian Ocean has some activity today in the form of Tropical Cyclone Two, a tropical storm with 45 mph winds that has formed in the Arabian Sea. Tropical Cyclone Two is expected to head west-northwest toward Oman and intensify into a Category 1 storm later this week, though the intensity forecast is a difficult one, due to moderate wind shear of 15 - 20 knots and the presence of dry air. The North Indian Ocean has two tropical cyclone seasons--one in May and June before the Southwest Monsoon arrives, and one in October - November after the Monsoon has departed.


Figure 2. True-color MODIS image from the Terra satellite of Tropical Cyclone Two over the Arabian Sea taken at approximately 6:30 am EDT June 10, 2014. The storm appears to be pulling in a plume of dust or pollution from the north, flowing off the coast of India (some sunglint reflecting off the water is making it difficult to tell for sure.) The coast of Oman can be seen at the left side of the image. Image credit: NASA.

Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis are predicting development over the coming five days. Strong upper-level winds, associated with the subtropical jet stream, are bringing high levels of wind shear over the tropical Atlantic and Gulf of Mexico, and these high winds are forecast to persist for at least the next six days. The GFS model continues to predict that about 7 - 10 days from now the upper level winds over the Western Caribbean will relax and low-level moisture will build, potentially allowing a tropical disturbance with heavy rains to develop there. However, the European model keeps the wind shear high over the Western Caribbean early next week, so any development in the region remains in doubt. Arguing against any development in the Atlantic is the anticipated strengthening next week in the West-Central Pacific Ocean of the Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days. An active MJO in that part of the tropics tends to bring large-scale sinking motion to the tropical Atlantic and increased wind shear, which puts a damper on the chances of tropical storm formation in the Atlantic. The MJO is predicted to drift slowly eastwards into the Eastern Pacific by late June, which will tend to keep odds of tropical storm formation lower than average in the Atlantic into late June.

Jeff Masters

Hurricane

Updated: 3:22 PM GMT on June 10, 2014

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Quiet in the Atlantic; 94E in Eastern Pacific Not a Threat to Land

By: JeffMasters, 2:26 PM GMT on June 09, 2014

There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis are predicting development over the coming five days (as I discussed in a blog post in August 2013, there are three models that have reasonable skill making forecasts of the genesis of new Atlantic tropical cyclones up to four days in advance--the European, GFS, and UKMET models.) Strong upper-level winds, associated with the subtropical jet stream, are bringing high levels of wind shear over the tropical Atlantic and Gulf of Mexico, and these high winds are forecast to persist for the remainder of the week. The GFS model predicts that about 8 - 11 days from now the upper level winds over the Western Caribbean will relax and low-level moisture will build, potentially allowing a tropical disturbance with heavy rains to develop there.


Figure 1. Wind shear forecast for 11 am EDT Saturday, June 14, 2014, made by the 06Z UTC June 9, 2014 run of the GFS model. The model predicts low shear less than 6 m/s (12 knots), the two lightest red colors, for the Eastern Pacific. However, in the Atlantic, strong upper level winds associated with the subtropical jet stream are predicted to bring high levels of wind shear in excess of 40 m/s (78 knots), yellow and orange colors, to the tropical Atlantic. Image is from our wundermap with the model layer turned on.

Eastern Pacific disturbance 94E no threat to land
In the Eastern Pacific, a tropical disturbance (94E) located about 150 miles south-southwest of Zihuatanejo, Mexico, is moving west-northwest, parallel to the coast, at about 5 - 10 mph. Satellite loops show that 94E has developed a large area of heavy thunderstorms with cold cloud tops that are showing rotation, and 94E is close to tropical depression status. In their 8 am EDT Tropical Weather Outlook, the National Hurricane Center (NHC) gave 94-E a 90% chance of developing into a depression or a named storm (Cristina) in the next five days. The bulk of 94E's heavy rains are expected to remain offshore of Mexico this week, and our most reliable track models, the GFS and European, show no threat to land this week.

Jeff Masters

Hurricane

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El Niño Odds Raised to 70% by NOAA, But El Niño is Actually Imminent

By: Michael Ventrice , 2:36 PM GMT on June 07, 2014

Today's guest blog post is by Dr. Michael Ventrice, an operational scientist for the Energy team at Weather Services International (WSI). This is a follow-up post to the ones he did on February 21 and April 4 on the progress of El Niño. Today's post is quite technical! - Jeff Masters

The June 5, 2014 El Niño update from NOAA's Climate Prediction Center gives a 70% chance that El Niño will form this summer, and an 80% by fall, but El Niño odds are higher than this. A strong Madden Julian Oscillation (MJO) event is forecast to develop over the central-eastern Pacific later this month in through early July (the Madden Julian Oscillation (MJO) is a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days.) This MJO location favors for another period of westerly wind bursts over the Central Pacific, an atmospheric signature that is likely to be the final kick needed for a blossoming El Niño event.

As I blogged about on February 21, there has been a noticeable warming in the eastern Pacific over the past few months in response to one of the most impressive downwelling oceanic Kelvin waves observed since satellite measurements began in the late 1970s. Recall that we observed a series of strong westerly wind bursts over the western-central Pacific Ocean this past winter. These westerly wind bursts can be tied to the state of the MJO as well as other equatorial waves and tropical cyclones.


Figure 1. A time-longitude plot of the departure from average of the depth of the 20°C isotherm shows the impressive nature of this downwelling oceanic Kelvin wave at the end of May, which had finally completed its trip all the way to the eastern Pacific Ocean. The series of these waves like has been observed in 2013 - 2014 is very typical of what one sees before the onset of an El Niño event. Note that since the downwelling oceanic Kelvin wave has emerged at the surface in recent weeks, we have seen a rise in the standard ENSO 3.4 index to anomalies approaching +0.5°C, which is the threshold for classification of El Niño conditions. Image credit: NOAA/CPC.


Figure 2. In our history, we have observed strong oceanic Kelvin waves to be driven by westerly wind bursts, which are often timed with the state of the MJO. Note in this time-longitude plot made during the onset of the 1997 super-El Niño, the shading is anomalous outgoing long wave radiation (OLR; thunderstorms are represented by blue shading), the convectively active phase of the MJO (coincides with low-level westerly winds) are represented by solid-red contours, and downwelling Oceanic Kelvin waves are indicated by the blue-solid contours. It is evident that consecutive MJO events play a critical role in facilitating a basin wide transition to El Niño. Note here time is going up!! Figure courtesy of Dr. Paul Roundy, SUNY Albany.



Figure 3. Departure of ocean temperature from average along the Equator in the Pacific Ocean on May 28, 2014 (top), shows an area of 5°C (8°F) ocean temperature anomalies at a depth of 50 - 150 meters, the signature of an oceanic Kelvin wave. In addition, warmer than average sea-surface temperatures extend along the Equator from South America all the way to the Date Line. This is a classic “Full-basin” El Niño expression. A time lapse is available here. Image credit: NOAA/CPC.

There is potential for a big MJO event this month
Over the past month, the MJO signature was relatively weak. During the latter half of May, we observed a period of enhanced trade flow (easterlies) over the eastern half of the Pacific Basin, which can often counter, or “stall” the El Niño for a period of time due to favoring a period of upwelling in the eastern part of the Basin. But while the atmosphere favored a weakening of the El Niño expression, the ocean did not a skip a beat. Warm ocean currents continue to rip towards the east, advecting warm waters from the western half of the basin to the east. The Pacific Warm Pool, which was well established in the western half of the basin for the past couple of years, has now shifted past the Date Line. You can watch the remarkable evolution of the eastward shifting Warm Pool on the Climate Prediction Center (CPC)’s link here.

Since the ocean remains in a state that is evolving towards El Niño, all we need is the atmosphere to behave…and it does appear that the atmosphere soon will! For the past five to six European weekly forecasts, the model has been becoming more and more aggressive with a developing MJO signature to push across the central-eastern Pacific later in June through early July. In response, we should expect another period of westerly wind bursts over the western-central part of the Basin. And what do you know, the model is keying on a period of anomalous lower-tropospheric flow that very well may be the final kick needed to facilitate a moderate-to-strong El Niño expression later this Fall. Forecast models continue to show the peak of the El Niño will occur later this Fall, with a magnitude near +1.5°C above average, as defined by the ENSO 3.4 Index. Now this is not a “Super El Niño” by any means, but it is very strong and there is still uncertainty regarding how strong it will get.


Figure 4. Weekly European model forecast of the MJO made over the past month have increasingly shown a strong MJO episode developing in late June and early July.

Regardless of what amplitude the ENSO 3.4 Index achieves, it only matters of the atmosphere responds. There are number of ways to identify the expression of El Niño in atmospheric data fields. One popular way is to look is to look at the Southern Oscillation Index (SOI), the difference in surface pressure between Darwin, Australia and the island of Tahiti. The SOI tends to drop to very low values during the presence of an El Niño atmosphere. This can be illustrated in the time-series below, where 1997 and 1982 marked the lowest points in the index over the past 35 years.


Figure 5. Southern Oscillation Index (SOI) from 1982 - 2014 shows the two strongest El Niño events of the past 35 years, in 1982 and 1997, had strongly negative SOIs.


Figure 6. The Southern Oscillation Index (SOI) for the past two years shows a downward trend in recent months, but has yet to cross into the sustained negative territory that will indicate the atmosphere has responded to warming SSTs in the equatorial Pacific.

My thoughts on this summer: Since the atmosphere has NOT yet locked into an “El Niño state”, we might expect the typical cooler-than-average summer conditions that the eastern 2/3 of the U.S. typically experiences during an El Niño event to be delayed. This means we can expect periods of hot weather across the major natural gas and power markets this summer. We do not believe these heat waves will be prolonged in nature, and it is difficult to pin-point the timing and magnitude of such events. But we can expect them to continue until the atmosphere “feels” the El Niño developing beneath in the ocean. With a possible strong MJO event on the horizon, it does suggest however that the atmosphere could lock into an El Niño state sometime between July and August.

Michael Ventrice

Dr. Michael Ventrice is an operational scientist for the Energy team at Weather Services International (WSI), who provide market-moving weather forecasts and cutting-edge meteorological analysis to hundreds of energy-trading clients worldwide. Follow the WSI Energy Team on Twitter at @WSI_Energy and @WSI_EuroEnergy.

Atmospheric Phenomena

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90L in Gulf of Mexico Bringing Heavy Rains to Mexico

By: JeffMasters, 2:15 PM GMT on June 06, 2014

Heavy rains continue to fall in Southeast Mexico due to a tropical disturbance in the Southern Gulf of Mexico's Bay of Campeche, Invest 90L. Satellite loops show that 90L has a well-defined surface circulation, but limited heavy thunderstorm activity. High wind shear of 30 knots, due to strong upper-level winds out of the west, is keeping all of 90L's heavy thunderstorms confined to the east side of the center. An ASCAT pass from last night showed 90L's strongest surface winds were near 35 mph, on the northeast side of the storm. Radar out of Alvarado, Mexico shows little in the way of well-organized low level spiral bands. Sea surface temperatures (SSTs) in the Southern Gulf of Mexico are about 28°, which is about 0.5° above average. These warm waters do not extend to great depth, and the total heat energy available to intensify a potential storm is rather low. The Hurricane Hunters have been given the order to investigate 90L on Friday afternoon at 3pm EDT.


Figure 1. Latest satellite image of Invest 90L over the Gulf of Mexico.

Forecast for 90L
90L appears to be drifting slowly to the west, and both the GFS and European model predict this motion will continue Friday and Saturday, bringing the storm ashore along the Mexican coast near Veracruz on Saturday. The 8 am EDT Friday run of the SHIPS model predicts that wind shear will stay high, 25 - 35 knots, over the Bay of Campeche through Sunday. None of the reliable genesis forecast models predict that 90L will develop into a tropical storm over the next five days. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave 2-day and 5-day odds of development of 50%. If 90L does develop, the strongest it would likely get is 45 mph sustained winds. The big threat from 90L is heavy rains, which will continue over Southeast Mexico into the weekend, causing flash flooding and dangerous mudslides.


Figure 2. Total precipitation recorded for the 24 hours ending at 8 am Thursday June 5, 2014. Rainfall amounts in the 24 hours ending at 8 am Thursday were as high as 8.78" (223 mm) at Palizada at the base of Mexico's Yucatan Peninsula. Thus far, there are no reports of deaths or heavy damage in Mexico from 90L or Tropical Storm Boris. Image credit: Conagua.

I'll have a new post on Saturday at the latest.

Jeff Masters

Hurricane

Updated: 2:26 PM GMT on June 06, 2014

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Invest 90L in Gulf of Mexico a Heavy Rain Threat for Mexico

By: JeffMasters, 2:28 PM GMT on June 05, 2014

A tropical disturbance in the Southern Gulf of Mexico's Bay of Campeche, Invest 90L, is nearly stationary, and is bringing a few heavy thunderstorms to the Gulf waters and Mexican shore along the Bay of Campeche. Satellite loops show that 90L is poorly organized, with a broad area of spin that is not well-defined, and only limited heavy thunderstorm activity. Radar out of Alvarado shows the storm has developed two low-level spiral bands near the coast that bear watching, though. Wind shear as diagnosed by University of Wisconsin CIMSS is a high 25 - 30 knots, which is keeping the system from developing. Sea surface temperatures (SSTs) in the Southern Gulf of Mexico are about 28°, which is about 0.5° above average. These warm waters do not extend to great depth, and the total heat energy available to intensify a potential storm is rather low. The Hurricane Hunters are on call to investigate 90L Thursday afternoon, if necessary.


Figure 1. Latest satellite image of Invest 90L over the Gulf of Mexico, and the remnants of Boris over Southeast Mexico.

Forecast for 90L
The 8 am EDT Thursday run of the SHIPS model predicts that wind shear will stay high over the Bay of Campeche through Sunday. Boris' remnants will be working their way northwards and arrive in the Bay of Campeche over the weekend, and the extra spin and moisture from Boris have the potential to aid development of 90L. However, none of the reliable genesis forecast models predict that 90L will develop over the next five days, and most of the models show the circulation moving westwards over land by Monday. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave 2-day and 5-day odds of development of 30%. The big threat from 90L is heavy rains, which will continue over Southeast Mexico into the weekend, causing flash flooding and dangerous mudslides. Several areas of 6 - 12" of rain fell in 24 hours over Mexico on Wednesday, thanks to the combined influences of 90L and Tropical Storm Boris. Boris made landfall in Southeast Mexico near 2 am EDT on Wednesday as a minimum-strength tropical storm with 40 mph winds, and dissipated Wednesday afternoon. Thus far, there are no reports of deaths or heavy damage in Mexico from the storm.


Figure 2. Total precipitation recorded for the 24 hours ending at 8 am Wednesday June 4, 2014. Image credit: Conagua.

Jeff Masters

Hurricane

Updated: 3:10 PM GMT on June 05, 2014

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Boris Hits Mexico; Atlantic's First Invest of 2014 Forms in Gulf of Mexico

By: JeffMasters, 2:56 PM GMT on June 04, 2014

Tropical Storm Boris made landfall near 2 am EDT Wednesday in Southeast Mexico as a tropical storm with 40 mph winds. The storm has weakened to a tropical depression and is expected to dissipate later today, but Boris remains an extremely dangerous rainfall threat to the region. Reports from the Mexican Weather Service indicate that the city of Tonala on the coast of Chiapas has recorded 12.5" (318 mm) of storm-total rainfall, and NHC is calling for rainfall totals of up to 20" from the storm. Tropical Storm Agatha hit this region at the end of May 2010 as a weak tropical storm with 45 mph winds, and dumped up to 22.27" of rain. The resulting catastrophic flash floods and landslides killed 190 and caused $1.1 billion in damage, mostly in Guatemala. Heavy rains from the precursors of Boris triggered a landslide in Guatemala over the weekend, killing five people.

Heavy rains from Boris are not the only weather hazard Mexico is dealing with. A brutal heat wave with the hottest temperatures ever recorded in June scorched the northern Mexican states of Sonora and Chihuahua on Tuesday. According to weather records researcher Maximiliano Herrera, monthly records for hundreds of stations with almost a century of data were beaten on Tuesday, some by as much as 5°C (8°F). The capital of the Sonora state, Hermosillo, hit 121°F (49.5°C) on Tuesday, the hottest temperature ever recorded in the city. The previous June record was 45.5°C, and the previous all-time record was 48.5°C.


Figure 1. Latest satellite image of Invest 90L over the Gulf of Mexico, and the remnants of Boris over Southeast Mexico.

Atlantic's first "Invest" of 2014 forms in Gulf of Mexico
The National Hurricane Center's first area of interest in the Atlantic for 2014 was designated on Wednesday morning in the Southern Gulf of Mexico's Bay of Campeche. Invest 90L is nearly stationary, but satellite loops show that 90L is kicking up some heavy thunderstorms along the Mexican coast. Wind shear as diagnosed by the 8 am EDT Wednesday run of the SHIPS model was high, 20 - 25 knots, and wind shear is expected to stay high over the Bay of Campeche through Saturday. By Sunday, wind shear is predicted to drop, and 90L may have a better chance to develop then. Boris' remnants will be working their way northwards and arrive in the Bay of Campeche over the weekend, and the extra spin and moisture from Boris have the potential to aid development of 90L. However, a band of high wind shear associated with strong upper-level winds from the subtropical jet stream is predicted to lie over the Central Gulf of Mexico, and these winds may interfere with development. Sea surface temperatures (SSTs) in the Southern Gulf of Mexico are about 28°, which is about 0.5° above average. These warm waters do not extend to great depth, and the total heat energy available to intensify a potential storm is rather low. SSTs cool quickly as one goes to the north, are a marginal 26°C in the Central Gulf of Mexico. None of the reliable genesis forecast models predict that 90L will develop over the next five days. In their 8 am EDT Wednesday Tropical Weather Outlook, NHC gave 2-day odds of development of 10% and 5-day odds of 20%. I put these odds at 20% and 30%, respectively, given the propensity of the Bay of Campeche to spin up tropical cyclones in recent years.

What is an "Invest"?
When a National Hurricane Center forecaster sees a tropical disturbance that may be a threat to develop into a tropical depression, the forecaster may label the disturbance an "Invest" and give it a tracking identification number. There is no formal definition of what qualifies as an "Invest". Declaring an "Invest" is merely done so that a set of forecasting aids like computer model track forecasts can be generated for the disturbance. The "Invest" is given a number 90-99, followed by a single letter corresponding to the ocean basin--"L" for the Atlantic, or "E" for the Eastern Pacific. Other warning agencies assign "Invests" for the other ocean basins--"W" for the Western Pacific, "A" for the Arabian Sea, etc. Detailed microwave and traditional satellite images are available for all "Invests" across the globe at the Navy Research Lab web site.


Figure 2. On June 1, 2014, sea surface temperatures in the Gulf of Mexico were a very warm 28°C in the southernmost Bay of Campeche on June 1, 2014, but diminished quickly to 26°C in the Central Gulf. Image credit: NOAA/AOML.

Jeff Masters

Hurricane

Updated: 3:40 PM GMT on June 04, 2014

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Boris a Dangerous Rainfall Threat for Mexico and Guatemala

By: JeffMasters, 3:29 PM GMT on June 03, 2014

Torrential rains are lashing Southeast Mexico and Southern Guatemala as Tropical Storm Boris lumbers northwards at about 5 mph, with landfall expected to occur Wednesday in Southeast Mexico. Even though Boris has top winds of just 40 mph, and will, at worst, be a weak tropical storm at landfall, it is an extremely dangerous rainfall threat to the region, as the storm's slow motion is expected keep heavy rains over the region the entire week. The NHC forecast is for 10 - 20" of rain with isolated amounts of 30 inches (750 mm) or more in the Mexican states of Oaxaca and Chiapas. Rains of this magnitude are capable of causing widespread flooding and heavy loss of life. Tropical Storm Agatha hit this region at the end of May 2010 as a weak tropical storm with 45 mph winds, and dumped up to 22.27" of rain. The resulting catastrophic flash floods and landslides killed 190 and caused $1.1 billion in damage, mostly in Guatemala. Heavy rains from the precursors of Boris triggered a landslide in Guatemala over the weekend, killing five people. In neighboring areas of Mexico, several landslides closed mountain roads on Monday, and evacuations began Monday evening from coastal and low-lying areas next to rivers that are prone to flooding.


FIgure 1. Latest satellite image of Boris.

Satellite images show that Boris is poorly organized, but has several clumps of heavy thunderstorms. Mexican radar showed the heaviest rains were offshore this morning, but these rains will move inland today as the storm heads north at 5 mph.


Figure 2. Satellite rainfall estimates for the 24-hour period ending Tuesday morning, June 3, 2014 over Central America. Rainfall amounts in excess of 200 mm (7.87") were estimated along the Guatemala coast and near the Belize/Mexico border. Image credit: http://climaya.com.

Will Boris emerge into the Gulf of Mexico late this week?
If Boris continues due north along its current path at its current speed for the remainder of the week, the storm will cross the narrowest part of Mexico and potentially emerge over the Southern Gulf of Mexico's Bay of Campeche late this week. Once over the warm waters of the Gulf, the remnants of Boris will have the potential to regenerate into a tropical depression. The 06Z Tuesday run of the SHIPS model, which uses the GFS model to diagnose wind shear, is predicting that wind shear in the Bay of Campeche will be moderate, 10 - 15 knots, on Friday and Saturday. However, a band of high wind shear associated with strong upper-level winds from the subtropical jet stream is predicted to lie over the Central Gulf of Mexico, and these winds may interfere with development. Sea surface temperatures (SSTs) in the Southern Gulf of Mexico are about 28°, which is about 0.5° above average. These warm waters do not extend to great depth, and the total heat energy available to intensify a potential storm is rather low. SSTs cool quickly as one goes to the north, are a marginal 26°C in the Central Gulf of Mexico. The GFS model is bullish on developing a tropical depression in the Gulf of Mexico late this week. But according to WSI's tropical weather expert Michael Ventrice, who has guest blogged on El Niño in my blog, the GFS likely has insufficient resolution to handle a large tropical low pressure system forecast to set up over Central American late this week. These large low pressure systems often have "spokes" of extra spin that rotate around the main low, and these "spokes" are often erroneously developed into tropical depressions by the GFS model. The European model is much less gung-ho about developing a tropical system in the Gulf of Mexico late this week, and NHC is currently giving no chance that such an event will happen by Sunday. I put the odds at 10%.


Figure 3. Sea surface temperatures in the Gulf of Mexico were a very warm 28°C in the southmost Bay of Campeche on June 1, 2014, but diminished quickly to 26°C in the Central Gulf. Image credit: NOAA/AOML.

Jeff Masters

Hurricane

Updated: 7:43 PM GMT on June 03, 2014

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Boldest Presidental Action Ever Taken to Combat Climate Change: EPA's New Regulations

By: JeffMasters, 8:13 PM GMT on June 02, 2014

President Obama's administration unveiled on Monday the "Clean Power Plan", a 645-page proposal to reduce carbon dioxide emissions from existing U.S. power plants under the 1970 Clean Air Act. The proposed regulations would reduce carbon dioxide emissions from these plants by 25% by 2020, compared to 2005 levels, and by 30% by 2030. The new regulations would hit the nation's 491 coal-fired power plants the most, since these plants account for 74% of the electric sector's carbon dioxide emissions, according to the Energy Information Administration. Coal burning supplies 37% of the nation's electric power, just behind natural gas.


Figure 1. On a hot day at Georgetown University, President Barack Obama removes his jacket before speaking about climate change on Tuesday, June 25, 2013. AP Photo.

The EPA plans to finalize the regulations by June 30, 2015, and states would have until June 2016 to submit their plans to the agency. Any American can comment on the proposed regulations here. The proposed regulations have already come under heavy fire from lawmakers in coal-producing states like West Virginia and Kentucky, and from industry-funded lobbying groups like the U.S. Chamber of Commerce, who warn of large job losses and economic costs. But in EPA administrator Gina McCarthy's June 2 speech, she touted that "the first year that these standards go into effect, we’ll avoid up to 100,000 asthma attacks and 2,100 heart attacks—and those numbers go up from there. In 2030, the Clean Power Plan will deliver climate and health benefits of up to $90 billion dollars. And for soot and smog reductions alone, that means for every dollar we invest in the plan, families will see $7 dollars in health benefits. And if states are smart about taking advantage of efficiency opportunities, and I know they are, when the effects of this plan are in place in 2030, average electricity bills will be 8 percent cheaper."

The Road to the Crucial 2015 Climate Change Summit In Paris
At the 2009 Copenhagen climate change negotiations, the U.S. committed to a goal of reducing nationwide greenhouse gas emissions by 17% below 2005 levels by 2020. Today's proposed regulations only affect the electric power sector, which is responsible for 40% of U.S. greenhouse gas emissions, so additional work will be needed to achieve this modest goal. Still, Obama's announcement today is the single most aggressive action any U.S. president has ever taken to reduce climate change, and will put the U.S. in a leadership position during the crucial December 2015 negotiations in Paris intended to forge a new legally binding global climate change treaty.

Jeff Masters

Climate Change Politics Climate Change

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The 2014 Atlantic Hurricane Season Begins

By: JeffMasters, 2:53 PM GMT on June 02, 2014

The 2014 Atlantic hurricane season is officially underway, and we already have an area of interest in the Gulf of Mexico to talk about. An area of low pressure over the Southern Gulf of Mexico's Bay of Campeche is generating disorganized heavy thunderstorm activity, and this area has a slight potential to develop late this week. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave the disturbance a 10% chance of developing by Saturday. The chances for this disturbance to develop depend heavily on the fate of an area of disturbed weather in the Eastern Pacific located a few hundred miles south of Southeast Mexico (Invest 93E), which will move slowly northwards towards the Gulf of Mexico this week. Satellite loops show a steady increase in the intensity and organization of the heavy thunderstorms associated with 93E, and the system is already bringing heavy rains to Southern Guatemala and Southeast Mexico. With the 8 am EDT Monday run of the SHIPS model showing light wind shear of 5 - 10 knots and warm ocean temperatures of 29.5°C for the remainder of the week along 93E's path, development into a tropical depression is likely. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave this system an 80% chance of developing into a tropical depression or tropical storm by Wednesday, and a 90% chance by Saturday. The 06Z Monday run of the GFS model predicts that this disturbance will make landfall in Southeast Mexico on Wednesday. The 00Z Monday European model is slower, predicting a Thursday landfall. It is possible that moisture and spin from 93E will aid the spin-up of a system over the Southern Gulf of Mexico late this week. In any case, residents of Southeast Mexico and Western Guatemala appear at risk to undergo a multi-day period of very heavy rainfall likely to cause flash flooding and dangerous mudslides.


Figure 1. Latest satellite image of Invest 93.

Summary of the 2014 Atlantic hurricane season forecasts
The major hurricane forecasting groups are not impressed with this season's potential to be an active one, and are calling for 2014 to be a below average to near-average year for the Atlantic. The most daring forecast was issued by Florida State, which calls for just 7 named storms and 4 hurricanes. The other groups are calling for 9 - 12 named storms. The main reason for the quiet forecasts is the likely emergence of El Niño. Every 3 - 7 years, variations in tropical winds and pressure shift warm ocean waters eastwards from the Western Pacific to the South American coast, causing an El Niño event. The unusually warm water tends to drive an atmospheric circulation that brings strong upper-level winds to the tropical Atlantic, creating high levels of wind shear that tend to tear hurricanes apart. Another factor leading to lower forecast numbers than in previous years is the fact that sea surface temperatures in the tropical Atlantic are near average this year--quite a bit cooler than we've seen during the typical year during our active hurricane period that began in 1995.


Figure 2. Departure of sea surface temperature (SST) from average for May 29, 2014. SSTs were near average over the Atlantic Main Development Region (MDR) for hurricanes, from the coast of Africa to Central America between 10°N and 20°N, including the Caribbean. As of June 2, 2014, SSTs over the region typically used to define El Niño events, 5°N - 5°S to 120°W - 170°W (the Niño 3.4 region) were at the threshold for El Niño conditions, +0.6°C from average, according to the latest weekly NOAA El Niño update. Image credit: NOAA/NESDIS.


Figure 3. Surface winds in the Atlantic Main Development Region (MDR) for hurricanes, from the coast of Africa to Central America between 10°N and 20°N, including the Caribbean, were stronger than average during the first four months of 2014. These winds stirred up more cooler water from the depths than usual, resulting in cooler sea surface temperatures than otherwise would have occurred. The stronger trade winds were due to a persistent positive phase of the North Atlantic Oscillation (NAO), which strengthened the semi-permanent high pressure system that lies over the Azores Islands, creating a stronger clockwise flow of air around the high. Image credit: NOAA/ESRL.

NOAA predicts a below-average hurricane season: 10.5 named storms
NOAA's May 22 Atlantic hurricane season forecast predicts a 50% chance of a below-normal season, a 40% chance of an near-normal season, and only a 10% chance of an above-normal season. They predict a 70% chance that there will be 8 - 13 named storms, 3 - 6 hurricanes, and 1 - 2 major hurricanes, with an Accumulated Cyclone Energy (ACE) 40% - 100% of the median. If we take the midpoint of these numbers, NOAA is calling for 10.5 named storms, 4.5 hurricanes, 1.5 major hurricanes, and an ACE index 70% of normal. This is below the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2013 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 151% of the median.

NOAA cites three key factors influencing their forecast for a below-normal to near-normal hurricane season:

1) An El Niño event is predicted for the summer and fall, which is expected to bring strong wind shear-inducing upper-level winds over the Tropical Atlantic. Vertical wind shear during the past 30 days was stronger than average across much of the Main Development Region (MDR) for hurricanes, from the coast of Africa to the Caribbean. Sinking air at mid-and upper-levels was also stronger than average. The development of El Niño would mean a likely continuation of these non-conducive conditions, and both versions of NOAA's long-range CFS model are predicting enhanced vertical wind shear across the western MDR during August-September-October 2014. Strong vertical wind shear and sinking motion, linked to a rare jet stream pattern of record strength, were key suppressing factors during the unexpectedly quiet 2013 Atlantic hurricane season.

2) Sea Surface Temperatures (SSTs) are near average in the MDR. Many long-range dynamical computer forecast models are predicting that SSTs in the MDR will remain near- or below-average throughout the hurricane season.

3) We are in an active hurricane period that began in 1995, and this positive phase of the Atlantic Multi-decadal Oscillation (AMO) may act to keep hurricane activity higher than it would otherwise be.

Colorado State predicts a below-average hurricane season: 10 named storms
A below-average Atlantic hurricane season is on tap for 2014, according to the June 2 seasonal hurricane forecast by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 10 named storms, 4 hurricanes, and 1 intense hurricane, and an Accumulated Cyclone Energy (ACE) of 65, about 2/3 of average. The forecast calls for a below-average chance of a major hurricane hitting the U.S., both along the East Coast (22% chance, 31% chance is average) and the Gulf Coast (23% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also below average, at 32% (42% is average.)

CSU's Analogue years: 2009, 2002, 1997, 1965, and 1957
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what they expect for this year: at least moderate El Niño conditions, neutral to slightly cool sea surface temperatures in the tropical Atlantic, and a positive phase of the Atlantic Multi-decadal Oscillation (AMO). Those five years were 2009, a quiet year with 9 named storms, 3 hurricanes, and 2 major hurricanes; 2002, which featured two major hurricanes that got their names retired: Lili and Isidore; 1997, a quiet year with only 8 named storms and 3 hurricanes; 1963, with 9 named storms and 7 hurricanes, including Cuba's deadliest hurricane of all-time: Hurricane Flora (8,000 killed); and 1957, a below-average year with 8 named storms and 2 major hurricanes, including June's deadly Hurricane Audrey, which was re-analyzed as a Category 3 storm this year. The average activity during these five analogue years was 9 named storms, 4 hurricanes, and 2 major hurricanes. The CSU team will issue an updated forecast on July 31, 2014.


Figure 4. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2004-2013, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2004 - 2013 climatology. Skill is poor for forecasts issued in December and April, modest for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.

TSR predicts a near-average hurricane season: 12 named storms
The May 27 forecast for the 2014 Atlantic hurricane season made by British private forecasting firm Tropical Storm Risk, Inc. (TSR) calls for a near-average season with 12 named storms, 5 hurricanes, 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 75. The long-term averages for the past 64 years are 11 named storms, 6 hurricanes, 3 intense hurricanes, and an ACE of 102. TSR rates their skill level as modest for these April forecasts: 7 - 15% higher than a "no-skill" forecast made using climatology. They project that 3 named storms will hit the U.S., with 1 of these being a hurricane. The averages from the 1950-2013 climatology are 3 named storms and 1 hurricane hitting the United States. TSR rates their skill at making these April forecasts for U.S. landfalls just 5% - 8% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects one named storm and no hurricanes in 2014. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR's two predictors for their statistical model are the forecast July - September trade wind speeds over the Caribbean and tropical North Atlantic, and the forecast August - September 2013 sea surface temperatures (SSTs) in the tropical North Atlantic Main Development Region (MDR) for hurricanes. Their model is calling for SSTs 0.32°C below average and trade winds 1 m/s stronger than average during these periods; both of these factors should act to decrease hurricane and tropical storm activity. The July-September 2014 trade wind prediction is based on an expectation of moderate El Niño conditions in August-September 2014. TSR will issue an updated forecast on May 27, 2014.

Penn State predicts a below-average hurricane season: 9 named storms
A statistical model by Penn State's Michael Mann, alumnus Michael Kozar, and researcher Sonya Miller is calling for a quiet Atlantic hurricane season with 9.3 named storms, plus or minus 3 storms. Their prediction was made using statistics of how past hurricane seasons have behaved in response to sea surface temperatures (SSTs), the El Niño/La Niña oscillation, the North Atlantic Oscillation (NAO), and other factors. The statistical model assumes that the mid-May 2014 0.29°C above average SSTs in the MDR will persist throughout hurricane season, a moderate El Niño will be in place, and the North Atlantic Oscillation (NAO) will be near average.

The PSU team has been making Atlantic hurricane season forecasts since 2007, and these predictions have done pretty well, except for in 2012, when an expected El Niño did not materialize. They were the only major forecast group that issued a successful 2013 Atlantic hurricane season forecast.

2007 prediction: 15 named storms, Actual: 15
2009 prediction: 12.5, named storms, Actual: 9
2010 prediction: 23 named storms, Actual: 19
2011 prediction: 16 named storms, Actual: 19
2012 prediction: 10.5 named storms, Actual: 19
2013 prediction: 16 named storms, Actual: 14

FSU predicts a below-average hurricane season: 7 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their sixth annual Atlantic hurricane season forecast on May 29, and went the lowest of any of the major forecast group: a 70% probability of 5 - 9 named storms and 2 - 6 hurricanes. The mid-point forecast is for 7 named storms, 4 hurricanes, and an accumulated cyclone energy (ACE) of 60. The scientists use a numerical atmospheric model developed at COAPS to understand seasonal predictability of hurricane activity. The model is one of only a handful of numerical models in the world being used to study seasonal hurricane activity and is different from the statistical methods used by other seasonal hurricane forecasters such as Colorado State, TSR, and PSU (NOAA uses a hybrid statistical-dynamical model technique.) The FSU forecast did well in 2009 - 2012, but badly missed the number of hurricanes in their 2013 prediction (8 predicted, but only 2 formed):

2009 prediction: 8 named storms, 4 hurricanes. Actual: 9 named storms, 3 hurricanes
2010 prediction: 17 named storms, 10 hurricanes. Actual: 19 named storms, 12 hurricanes
2011 prediction: 17 named storms, 9 hurricanes. Actual: 19 named storms, 7 hurricanes
2012 prediction: 13 named storms, 7 hurricanes. Actual: 19 named storms, 10 hurricanes
2013 prediction: 15 named storms, 8 hurricanes. Actual: 14 named storms, 2 hurricanes

UK Met Office predicts a below-average hurricane season: 10 named storms
The UKMET office forecast for the 2014 Atlantic hurricane season, issued May 16, calls for below-average activity, with 10 named storms, 6 hurricanes, and an ACE index of 84. In contrast to the statistical models relied upon by CSU, TSR, PSU, and NOAA, the UKMET forecast is done strictly using two dynamical global seasonal prediction systems: the Met Office GloSea5 system and ECMWF system 4. Their forecasts for the past two years have not verified well:

2012 prediction: 10 named storms, ACE index of 90; Actual: 19 named storms, ACE index of 123
2013 prediction: 14 named storms, 9 hurricanes, ACE index of 130; Actual: 14 named storms, 2 hurricanes, ACE index of 31

Predictions from WU, WSI, and NC State
Weather Underground Community Hurricane Forecast: 12 named storms, 5 hurricanes, 2 major hurricanes
WSI: 11 named storms, 5 hurricanes, 2 major hurricanes
North Carolina State: 9.5 named storms, 5 hurricanes, 2 major hurricanes

Even a quiet hurricane season can be devastating
Quiet hurricane seasons with below-average activity can still produce major hurricanes that cause massive devastation. The five seasons that CSU lists as analogue years for 2014 produced four hurricanes that had their names retired, including one that killed 8,000 people in Cuba (Flora of 1963) and one that killed over 400 people in Texas and Louisiana (Audrey of 1957.) Even if an El Niño does develop this year, that doesn't mean it will be a quiet season. Recall the El Niño year of 2004, when four major hurricanes pounded the U.S.--Ivan, Charlie, Jeanne, and Frances. Those of you in Hurricane Alley should prepare for the 2014 season the same way you would for a predicted hyperactive season, and be ready for the Storm of the Century to hit your location.

Jeff Masters

Hurricane

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