Dr. Jeff Masters' WunderBlog

Hurricane season draws to a close

By: JeffMasters, 1:01 PM GMT on November 29, 2010

November 30 marks the final day of the 2010 Atlantic hurricane season--a strange and highly active season. While it was an exceptionally active year, with 19 named storms, 12 hurricanes, and 5 intense hurricanes, deaths and damages were far below what one would expect from so much activity. To me, this year is most memorable for what didn't happen--we did not get a full fledged hurricane rip through the Deepwater Horizon oil spill, nor did a devastating hurricane cause massive loss of life in Haiti's vulnerable earthquake zone. However, two hurricanes from this year are virtually certain to get their names retired--Tomas and Igor--and two other storms that did billions of damage to Mexico, Karl and Alex, are likely to have their names retired, as well.

The 19 named storms, 12 hurricanes, and 5 intense hurricanes were 198%, 203%, and 217% of the 1950-2000 average for named storms, hurricanes and major hurricanes, respectively. The nineteen named storms ties 2010 with 1995 and 1887 for 3rd place for most number of named storms in an Atlantic hurricane season. Only 2005 (28 named storms) and 1933 (21 named storms) were busier (Atlantic hurricane records go back to 1851, though there were likely many missed named storms prior to the beginning of satellite coverage in the mid-1960s.) This year also featured twelve hurricanes, tying 2010 with 1969 for second place for most hurricanes in a season. The record is held by 2005 with fifteen hurricanes. The five major hurricanes this year puts us in a tie for ninth place for most major hurricanes in a season. This year's Accumulated Cyclone Energy (ACE) index was 163, putting it in 13th place for ACE since 1944. A "hyperactive" hurricane season is considered to have an ACE index of >175% of the median. According to Wikipedia, median ACE measured over the period 1951–2000 for the Atlantic basin was 87.5, so 2010 is a hyperactive year by that definition (183% of the median.)



Friendly steering currents for the U.S.
As active as the 2010 season was, only one weak tropical storm made a direct landfall on the U.S. (Tropical Storm Bonnie, which hit South Florida in August as minimal tropical storm with 40 mph winds.) During the 15-year active hurricane period from 1995 - 2009, 33% of all named storms in the Atlantic hit the U.S., and 30% of all Atlantic hurricanes hit the U.S. at hurricane strength. Thus, the U.S. should have expected the landfall of six named storms, four of them being hurricanes, and two being intense hurricanes. So, the U.S. really lucked out this year. For comparison, here's how the U.S. fared in the four other hurricane seasons as busy or more busy:

2005: 28 storms, 7 hit the U.S. (5 were hurricanes, and 4 of those major hurricanes)
1933: 21 storms, 7 hit the U.S. (5 were hurricanes, and 3 of those were major hurricanes)
1995: 19 storms, 5 hit the U.S. (2 were hurricanes, and 1 was major)
1887: 19 storms, 5 hit the U.S. (3 were hurricanes, no majors)

We had twelve hurricanes in the Atlantic in 2010, yet none of them struck the U.S. Since 1900 there is no precedent of an Atlantic hurricane season with ten or more hurricanes where none has struck the U.S. as a hurricane. The eleven previous seasons with ten or more hurricanes--1870, 1878, 1886, 1893, 1916, 1933, 1950, 1969, 1995, 1998, and 2005--each had at least two hurricane strikes on the U.S. Since hurricane Ike (2008), there have been eighteen consecutive non US-landfalling hurricanes. Such a sequence last happened between Irene (1999) and Lili (2002), with 22 consecutive non US-landfalling hurricanes, and between Allen (1980) and Alicia (1983) with seventeen consecutive non US-landfalling hurricanes (thanks go to Adam Lea of tropicalstormrisk.com for these stats.)

No major Category 3 and stronger hurricanes have hit the U.S. since Hurricane Wilma of 2005. This is just the third such major hurricane drought since 1851. The other two such 5-year major hurricane droughts were 1901 - 1905 and 1910 - 1914. Also, 2010 is the only year besides 1951 when there have been five major hurricanes in the Atlantic, and none have hit the U.S. (1958 is also listed as such a year, but preliminary results from a re-analysis effort shows that Hurricane Helene hit North Carolina as a major hurricane that year.) There has never been a six year period without a U.S. major hurricane landfall.

The reason the U.S. got so lucky--and that Canada and Mexico took a much more severe beating than usual--was that the Azores/Bermuda high was farther east than usual, and there were more strong troughs of low pressure over the U.S. East Coast than usual. In addition, there was stronger high pressure than usual over the U.S. Gulf Coast, which deflected Caribbean storms into Mexico.

Intense hurricanes in unprecedented locations
Another remarkable feature of this year was that we saw three major hurricanes in rare or unprecedented locations. Julia was the easternmost major hurricane on record, Karl was the southernmost major hurricane on record in the Gulf of Mexico, and Earl was the 4th strongest hurricane so far north. This unusual major hurricane activity is likely due, in part, to the record tropical Atlantic sea surface temperatures this year. Sea surface temperatures in the tropical Atlantic from the Caribbean to the coast of Africa were at their warmest levels on record for almost the entire year.

Rare simultaneous hurricane occurrences and activity levels
On September 16, there were three simultaneous hurricanes--Karl, Igor, and Julia--in the Atlantic. According to Phil Klotzbach at Colorado State, three simultaneous Atlantic hurricanes is a rare phenomena, having occurred only eight other times since 1851. The other years were 1893, 1926, 1950, 1961, 1967, 1980, 1995, and 1998. Two of those years--1998 and 1893--had four simultaneous hurricanes.


Figure 2. Triple trouble: From left to right, Hurricanes Karl, Igor, and Julia roil the Atlantic. Image credit: NASA/GSFC.

On September 15, Hurricane Julia and Hurricane Igor were both Category 4 storms. This was just the second time in recorded history that two simultaneous Category 4 or stronger storms have occurred in the Atlantic. The only other occurrence was on 06 UTC September 16, 1926, when the Great Miami Hurricane and Hurricane Four were both Category 4 storms for a six-hour period. The were also two years, 1999 and 1958, when we missed having two simultaneous Category 4 hurricanes by six hours. The four Category 4 storms in 2010 makes this year tied for third place for most Category 4+ storms in a year. Only two other seasons have had as many as five Category 4 or stronger storms (2005 and 1999). This year is also holds the record for the earliest a fourth Category 4 or stronger storm has formed (though the fourth Category 4 of 1999, Hurricane Gert, formed just 3 hours later on September 15 in 1999.) We also had four Cat 4+ storms in just twenty days, which beat the previous record for shortest time span for four Cat 4+ storms to appear. The previous record was 1999--24 days. Eleven named storms formed between August 22 and September 29. This is the most named storms to form during this period, breaking the old record of nine named storms set in 1933, 1949, 1984 and 2002 (thanks go to Phil Klotzbach of CSU for the last two stats.)

Rare activity levels
Five hurricanes formed during the month of October. Only 1870 (six hurricanes) and 1950 (five hurricanes) have had five or more October hurricanes. We also had four Cat 4+ storms in just twenty days, which beat the previous record for shortest time span for four Cat 4+ storms to appear. The previous record was 1999--24 days. Eleven named storms formed between August 22 and September 29. This is the most named storms to form during this period, breaking the old record of nine named storms set in 1933, 1949, 1984 and 2002 (thanks go to Phil Klotzbach of CSU for the last two stats.)

Hurricane Alex
Hurricane Alex had the highest sustained winds (100 mph) of any June hurricane since Hurricane Alma of 1966 (125 mph.)

Hurricane Earl
As Hurricane Earl approached North Carolina on September 2, its 140 mph winds made it the fourth strongest Atlantic hurricane on record so far north. Only Hurricane Esther of 1961, Hurricane Connie of 1955, and Hurricane Two of 1922 had stronger winds at a more northerly latitude.


Figure 2. Hurricane Earl as seen from the International Space Station on Thursday, September 2, 2010. Image credit: NASA astronaut Douglas Wheelock.

Hurricane Igor: Newfoundland's worst hurricane in memory
Igor killed one person on Newfoundland, and damage exceeded $100 million, making Igor the most damaging tropical cyclone in Newfoundland history. A summary of the impact of Igor prepared by Environment Canada put it this way:

"Hurricane Igor and its severe impacts certainly represent a rare event in Newfoundland history which has been described as the worst in memory. In statistical terms, this was effectively a 50 - 100 year event depending on how one chooses to define it. There are no hurricanes/post tropical events of this magnitude striking Newfoundland in the modern era. Hurricane Juan in Nova Scotia was the last Atlantic Canadian hurricane to cause extreme damage. Prior to the naming of hurricanes, the 1935 Newfoundland Hurricane 75 years ago was of similar intensity."


Figure 3. A ravine carved by Hurricane Igor's flood waters washed out the Trans-Canada Highway, isolating Southeast Newfoundland from the rest of the province. Image credit: CBC News.

Hurricane Julia: strongest hurricane so far east
Hurricane Julia put on a remarkable and unexpected burst of intensification to become the season's fourth Category 4 storm. Julia's 135 mph winds made it the strongest hurricane on record so far east; the previous record was held by the eighth storm of 1926, which was only a 120 mph Category 3 hurricane at Julia's longitude. Julia's intensification was a surprise, since SSTs in the region were about 27.5°C, which is just 1°C above the threshold needed to sustain a Category 1 hurricane.

Hurricane Karl: strongest hurricane ever in the Bay of Campeche
Hurricane Karl was the first major hurricane on record in the Gulf of Mexico's Bay of Campeche--the region bounded by the Yucatan Peninsula on the east. There were two other major hurricanes that grazed the northern edge of the Bay of Campeche, Hurricane Hilda of 1955 and Hurricane Charley of 1951, but Karl is by far the farthest south a major hurricane has been in the Gulf of Mexico. Hurricane records go back to 1851, but Karl was a small storm and could have gotten missed as being a major hurricane before the age of aircraft reconnaissance (1945). Flooding from Karl caused an estimated $5.6 billion in damage to Mexico, making Karl this year's most damaging storm.


Figure 4. Tracks of all major hurricanes since 1851 near Mexico's Bay of Campeche. Karl is most southerly storm on record in the Gulf of Mexico. Image credit: NOAA Coastal Services Center.

Hurricane Paula sets a rapid intensification record
Hurricane Paula, the 16th named storm and 9th hurricane of the season, set a modern record for the fastest intensification from the issuance of the first advisory to hurricane strength. Paula reached hurricane strength just twelve hours after the first advisory was issued. Since reliable record keeping of intensification rates of Atlantic hurricanes began in 1970, when regular satellite coverage became available, no storm has ever intensified into a hurricane that quickly. Hurricane Humberto of 2007 held the previous record for fastest intensification from first advisory issued to hurricane strength--18 hours. However, there is one caveat to keep in mind. It is likely that when the final Atlantic hurricane data base (HURDAT) is constructed, Paula will be recognized as having been a tropical depression 3 - 9 hours before the first advisory was issued. Thus, it may turn out that Paula will be recognized as intensifying from first advisory to a hurricane in eighteen hours, tying Humberto's record. There have been six storms that accomplished the feat in 24 hours.

Hurricane Tomas
The formation of Tomas so far south and east so late in the season (October 29) is unprecedented in the historical record; no named storm has ever been present east of the Lesser Antilles (61.5°W) and south of 12°N latitude so late in the year. Hurricane Six of 1896 came close--it was also a tropical storm south of 12°N and east of 61.5°W on October 29, but nine hours earlier in the day. That storm recurved to the north and missed the Lesser Antilles. Tomas' track through the southern Lesser Antilles so late in the year is unprecedented. Another unusual aspect of Tomas' formation is that we had simultaneous hurricanes in the Atlantic Ocean on October 30--Tomas and Shary. There has been only one hurricane season since 1851 that had two simultaneous hurricanes later in the year--1932, when Hurricane Ten and Hurricane Eleven both existed November 7 - 10. Tomas was the 6th deadliest late-season Atlantic hurricane on record, and its preliminary death toll of 31 - 41 makes it the deadliest storm of the 2010 season. Tomas killed at least nine people and did at least $100 million in damage to St. Lucia, making it that island's second most damaging storm on record.


Figure 5. This landslide on St. Lucia after Tomas destroyed an art studio located just below the white car, killing several people. Image credit: Bernd Rac, Anse Chastanet.

Pre-season forecasts do well
Phil Klotzbach and Bill Gray of CSU have a more in-depth summary of this year's hurricane season. Kudos to them and all the other seasonal forecasting groups, whose forecasts of an exceptionally active Atlantic hurricane season were spot-on. CSU will make their first forecast for the 2011 hurricane season on Wednesday, December 12.

Jeff Masters

Hurricane

Updated: 4:51 PM GMT on April 19, 2011

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Forecast for the winter of 2010 - 2011

By: JeffMasters, 5:38 PM GMT on November 24, 2010

Meteorological winter officially begins on December 1, but winter has begun a week early across much of North America, thanks to a significant cold blast that has broken dozens of daily low temperature records across much of western Canada and the Western U.S. Sheridan, Wyoming set a new record for the date this morning with -17°F, and Oakland California had its coldest November 24th with a reading of 34°F this morning. The cold blast is expected to be short-lived, though, with near-average conditions returning by the weekend. The long-range 1 - 2 week forecasts from the GFS and ECMWF models do not show the jet stream getting "stuck" in place for the beginning of meteorological winter next week, and it appears that the first two weeks of winter will be rather ordinary.


Figure 1. Forecast temperature and precipitation for the U.S. for the upcoming winter, as predicted by NOAA.

Latest winter forecast from NOAA
We currently have moderate La Niña conditions over the tropical Pacific ocean, which means that a large region of cooler than average waters exists along the Equator from the coast of South America to the Date Line. Cooler than average waters in this location tend to deflect the jet stream such that the Pacific Northwest experiences cooler and wetter winters than average, while the southern U.S. sees warmer and drier winter weather. NOAA's forecast for the upcoming winter issued on October 21 calls for a typical La Niña winter over the U.S.--warm and dry over the southern portion of the country, cool and wet over the Pacific Northwest, warmer and wetter than average over the Ohio Valley, and near average over the remainder of the country. According to NOAA's latest La Niña discussion, La Niña is expected to remain solidly entrenched throughout the coming winter and into spring.


Figure 2. Observed temperature and precipitation departures from average for the last three winters with a La Niña in the "moderate" or "strong" category. The current La Niña is right at the borderline between "moderate" and "strong." The anomaly patterns from the past three La Niña winters were dominated by the winter of 1999 - 2000, which was the warmest winter in U.S. history, and 1998 - 1999, which was the 2nd warmest in U.S. history. Image credit: NOAA/ESRL.

What happened during the last three La Niña winters?
The last three winters with moderate to strong La Niña conditions occurred in 2007 - 2008, 1999 - 2000, and 1998 - 1999. These winters were extremely variable. The most recent La Niña winter, in 2007 - 2008, was near average in temperature and precipitation; the other two winters were the two warmest winters in U.S. history. The winter of 1998 - 1999 set a world record for the greatest seasonal snowfall in history, when a seemingly endless parade of winter storms across the Pacific Northwest left an astonishing 1,140 inches (95 feet) of snow at Mt. Baker in northwestern Washington. It's worth noting that two of these three La Niña winters (2007 - 2008 and 1998 - 1999) saw record levels of tornado activity. Of the three winters, I believe that the winter of 2007 - 2008 may be the best historical analogue for the coming winter, since Arctic sea ice loss, which can significantly affect winter weather, was most similar to the conditions observed this year.

A look back at the winter of 2007 - 2008
The La Niña winter of 2007 - 2008 started slowly, but ended up piling up quite a bit of snow across much of the U.S. New York experienced its wettest winter on record, and Colorado, Connecticut, Pennsylvania, and Vermont had their second wettest winter on record. As is typical during a La Niña winter, Texas was drier than normal, but the rest of the south had near-average precipitation.

According to The Northern Tier Rules: The 2007-2008 Snow Report by David Robinson, Weatherwise, Mar-Apr 2009, eleven major cities reported more than 125 percent of average snowfall. This compares with only three in 2006-2007, and was the most since thirteen cities in 2003-2004.

Record high snow seasons occurred in Madison, Wisconsin (101.4 inches, previous record of 76.1 inches in 1978-1979); Youngstown, Ohio (102.8 inches, previous record of 90.2 inches in 2005-2006); and Caribou, Maine (197.8 inches, previous record of 181.1 inches in 1954-1955). Two stations came very close to establishing seasonal seasonal records; Spokane, Washington, 92.6", 0.9" below the 1949-1950 record, and Flint, Michigan, 82.8", just 0.1" below the record set in 1974-1975.


Figure 3. Snowfall totals for the winter of 2007 - 2008. Image credit: The Northern Tier Rules: The 2007-2008 Snow Report by David Robinson, Weatherwise, Mar-Apr 2009.

Wildcard number 1: What will the NAO do?
The North Atlantic Oscillation (NAO) is a climate pattern in the North Atlantic Ocean of fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores High. It is one of oldest known climate oscillations--seafaring Scandinavians described the pattern several centuries ago. Through east-west oscillation motions of the Icelandic Low and the Azores High,the NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. Negative NAO winters tend to bring cold winters to Europe, and the prevailing storm track moves south towards the Mediterranean Sea. This brings increased storm activity and rainfall to southern Europe and North Africa.

The winter of 2009 - 2010 had the most extreme negative NAO since record keeping began in 1950. The NAO index was -1.67, beating the previous record of -1.47 set in the winter of 1962 - 1963. The record negative NAO was responsible for unusual cold weather and snows over Eastern North America and Europe, and resulted in an upside-down winter: coldest in 25 years in the U.S., and warmest on record in Canada, with snow needing to be trucked in for the Winter Olympics in Vancouver. This "Warm Arctic-Cold Continents pattern" had occurred previously only three times in the past 160 years. If a strong negative NAO establishes itself this winter, we could have a winter like 1995 - 1996, which featured a weak La Niña and a strongly negative NAO. That winter featured many cold air outbreaks across the Eastern U.S., resulting in fifteen major cities setting new all-time seasonal snowfall total, including 75.6" at New York City's Central Park. Unfortunately, the NAO is not predictable more than about two weeks in advance.

Wildcard number 2: How will Arctic sea ice loss affect the winter?
NOAA issued their annual Arctic Report Card last month, and discussed the fact that recent record sea ice loss in the summer in the Arctic is having major impacts on winter weather over the continents of the Northern Hemisphere. The Report Card states, "There continues to be significant excess heat storage in the Arctic Ocean at the end of summer due to continued near-record sea ice loss. There is evidence that the effect of higher air temperatures in the lower Arctic atmosphere in fall is contributing to changes in the atmospheric circulation in both the Arctic and northern mid-latitudes. Winter 2009-2010 showed a new connectivity between mid-latitude extreme cold and snowy weather events and changes in the wind patterns of the Arctic; the so-called Warm Arctic-Cold Continents pattern...With future loss of sea ice, such conditions as winter 2009-2010 could happen more often. Thus we have a potential climate change paradox. Rather than a general warming everywhere, the loss of sea ice and a warmer Arctic can increase the impact of the Arctic on lower latitudes, bringing colder weather to southern locations." As a specific example of what the Report Card is talking about, Francis et al. (2009) found that during 1979 - 2006, years that had unusually low summertime Arctic sea ice had a 10 - 20% reduction in the temperature difference between the Equator and North Pole. This resulted in a weaker jet stream with slower winds that lasted a full six months, through fall and winter. The weaker jet caused a weaker Aleutian Low and Icelandic Low during the winter, resulting in a more negative North Atlantic Oscillation (NAO), allowing cold air to spill out of the Arctic and into Europe and the Eastern U.S. Thus, Arctic sea ice loss may have been partially responsible for the record negative NAO observed during the winter of 2009 - 2010, and the emergence of the "Warm Arctic-Cold Continents pattern." This pattern is kind of like leaving the refrigerator door ajar--the refrigerator warm up, but all the cold air spills out into the house. If the Arctic Report Card is right, we'll be seeing more of this pattern during coming winters--possibly even during the winter of 2010 - 2011.

Summary
I'm often asked by friends and neighbors what my forecast for the coming winter is. My reply is usually, "Flip a coin. We don't have the capability to make very skillful predictions of the coming winter." I'll share with you my hunch for this winter, though--we are due for a rather ordinary La Niña winter like we had in 2007 - 2008. After a year of some extraordinary extreme weather, we are overdue for a relatively quiet season or two of weather.

For more information
Golden Gate Weather has a nice set of imagery showing historic La Niña winter impacts, based on whether it was a "weak", "moderate", or "strong" event.

Francis, J. A., W. Chan, D. J. Leathers, J. R. Miller, and D. E. Veron, 2009: Winter northern hemisphere weather patterns remember summer Arctic sea-ice extent. Geophys. Res. Lett., 36, L07503, doi:10.1029/2009GL037274.

Honda, M., J. Inoue, and S. Yamane, 2009: Influence of low Arctic sea-ice minima on anomalously cold Eurasian winters. Geophys. Res. Lett., 36, L08707, doi:10.1029/2008GL037079.

Overland, J. E., and M. Wang, 2010: Large-scale atmospheric circulation changes associated with the recent loss of Arctic sea ice. Tellus, 62A, 1.9.

Petoukhov, V., and V. Semenov, 2010: A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents. J. Geophys. Res.-Atmos., ISSN 0148-0227.

Seager, R., Y. Kushnir, J. Nakamura, M. Ting, and N. Naik (2010), Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10, Geophys. Res. Lett., 37, L14703, doi:10.1029/2010GL043830.

Next post
Thanksgiving break is at hand, and I plan to spend it enjoying family and friends, eating far too much delicious food, and watching the invincible juggernaut that is my favorite football team, the Detroit Lions, demolish yet another hapless opponent on Thanksgiving Day (not!) I'm also looking forward to seeing the season's first snowflakes here in Michigan on Friday--winter has been late arriving here this year. I'll be back with a new post on Monday. Have a great Thanksgiving, everyone!

Jeff Masters

Winter Weather

Updated: 5:40 PM GMT on November 24, 2010

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Bolivia ties its all-time heat record

By: JeffMasters, 1:25 PM GMT on November 23, 2010

Bolivia tied its all-time hottest temperature mark on October 29, when the mercury hit 46.7°C (116.1°F) at Villamontes. This ties the record set in Villamontes on three other dates: November 9, 2007, November 1980, and December 1980.

The year 2010 now has the most national extreme heat records for a single year--nineteen, plus one island territory, the UK's Ascension Island. These nations comprise 20% of the total land area of Earth. This is the largest area of Earth's surface to experience all-time record high temperatures in any single year in the historical record. Looking back at the past decade, which was the hottest decade in the historical record, seventy-five counties set extreme hottest temperature records (33% of all countries.) For comparison, fifteen countries set extreme coldest temperature records over the past ten years (6% of all countries). My source for extreme weather records is the excellent book Extreme Weather by Chris Burt. His new updates (not yet published) remove a number of old disputed records. Keep in mind that the matter of determining extreme records is very difficult, and it is often a judgment call as to whether an old record is reliable or not. The World Meteorological Organization is currently in the process of contacting all nineteen of the nations I list here to see if the records can be officially verified. So far, the records in Finland and Pakistan have been officially verified, and it appears likely that the records in Belarus and Ukraine will also have official sanction.


Figure 1. Climate Central put together a nice graphic showing the nations that have set new extreme heat records in 2010, which I've updated to include Bolivia.

Other national all-time extreme heat records set in 2010
Zambia recorded its hottest temperature in history Wednesday, October 13, when the mercury hit 42.4°C (108.3°F) in Mfuwe. The previous record was 42.3°C (108.1°F) set on November 17, 2005 in Mfuwe.

Belarus recorded its hottest temperature in its history on August 6, 2010, when the mercury hit 38.9°C (102.0°F) in Gorky. The previous record was 38.0°C (100.4°F) set at Vasiliyevichy on Aug. 20, 1946.

Ukraine recorded its hottest temperature in its history when the mercury hit 42.0°C (107.6°F) at Lukhansk on August 12, 2010. The previous record was set at the same location on August 1, 2010--41.3°C (106.3°F). Ukraine also reached 41.3°C on July 20 and 21, 2007, at Voznesensk.

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

Finland recorded its hottest temperature on July 29, 2010, when the mercury hit 37.2°C (99°F) at Joensuu. The old (undisputed) record was 95°F (35°C) at Jyvaskyla on July 9, 1914. The previous official record was 35.9°C at Turku in July 1914, but this reading has been disputed by weather records researcher Maximiliano Herrera as being unreliable due improper siting of the instrument too close to tall buildings.

Qatar had its hottest temperature in history on July 14, 2010, when the mercury hit 50.4°C (122.7°F) at Doha Airport. The previous record was 49.6°C in July 2000 at the same location. There are other stations in Qatar,but only the Doha International Airport has reliable data.

Russia had its hottest temperature in history on July 12, when the mercury rose to 45.4°C (113.7°F) at the Utta hydrological station in the Kalmykia Republic, in the European portion of Russia near the Kazakhstan border. This station is not under control of the Russian meteorological service, and may not be 100% reliable. A reading of 44.0°C (111.2°F) was also recorded in Yashkul, Kalmykia Republic, on July 11. The previous hottest temperature in Russia (not including the former Soviet republics) at a non-automated station was the 43.8°C (110.8°F) reading measured at Alexander Gaj, Kalmykia Republic, on August 6, 1940. The previous hottest temperature at an automated station was 45.0°C recorded in August 1940 at El'ton. The remarkable heat in Russia this year has not been limited just to the European portion of the country--the Asian portion of Russia also recorded its hottest temperature in history this year, a 42.7°C (108.9°F) reading at Ust Kara, in the Chita Republic on June 27. The 42.3°C (108.1°F) reading on June 25 at Belogorsk, near the Amur River border with China, also beat the old record for the Asian portion of Russia. The previous record for the Asian portion of Russia was 41.7°C (107.1°F) at Aksha on July 21, 2004.

Sudan recorded its hottest temperature in its history on June 22 when the mercury rose to 49.7°C (121.5°F) at Dongola. The previous record was 49.5°C (121.1°F) set in July 1987 in Aba Hamed.

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

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

Chad had its hottest day in history on June 22, 2010, when the temperature reached 47.6°C (117.7°F) at Faya. The previous record was 47.4°C (117.3°F) at Faya on June 3 and June 9, 1961, but old readings at this station, particularly in the 1950s, were affected by over-exposure of the instrument to sun.

Kuwait recorded its hottest temperature in history on June 15 in Abdaly, according to the Kuwait Met office. The mercury hit 52.6°C (126.7°F). Kuwait's previous all-time hottest temperature was 51.9°C (125.4°F), on July 27,2007, at Abdaly. Temperatures reached 51°C (123.8°F) in the capital of Kuwait City on June 15, 2010. There were some readings as high as 54°C at Mitribah this summer, but the intrument there was found to be out of calibration.

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

Pakistan had its hottest temperature in history on May 26, when the mercury hit an astonishing 53.5°C (128.3°F) at the town of MohenjuDaro, according to the Pakistani Meteorological Department. While this temperature reading must be reviewed by the World Meteorological Organization (WMO) for authenticity, not only is the 128.3°F reading the hottest temperature ever recorded in Pakistan, it is the hottest reliably measured temperature ever recorded on the continent of Asia. The old Pakistani record was 52.8°C (127°F) at Jacobabad in 1919.

Myanmar (Burma) had its hottest temperature in its recorded history on May 14, when the mercury hit 47.2°C (117.0°F) in Myinmu. This broke the record of 47.0°C set at the same location two days previous (May 12.) Myanmar's previous hottest temperature was 46.0°C (114.4°F) at Magwe in May, 1980. According to Chris Burt, author of the authoritative weather records book Extreme Weather, the 47.2°C measured this year is the hottest temperature in Southeast Asia history.

Nigeria had its hottest temperature in history on April 3, 2010, when the mercury hit 46.4°C (115.6°F) at Yola..

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

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

Colombia had its hottest reliably measured temperature in history on January 24, 2010, when Puerto Salgar hit 42.3°C (108°F). The previous record was 42.0°C (107.6°F) at El Salto in March 1988 and April 1998 (exact day unknown.)

Also Notable
China set its all-time heat record for an inhabited place on June 20, 2010, when the mercury hit 48.7°C (119.7°F) at Toyoq. The all-time heat record for China is 49.7°C (121.5°F) on August 3, 2008 at the Aydingkol automatic weather station at the uninhabited Ading Lake in the Turfan Depression in Northwest China.

Martinique, an island in the Caribbean that is a French territory, set what may be its hottest reliably measured temperature record in September, when the mercury hit 36.2°C (97.2°F) at Francois Chopotte. The current all-time record is 36.5°C (97.7°F) in April 1983 at St. Pierre Observatory, but this measurement was taken with older equipment that may not be reliable.

The occupied west bank of Palestine, the portion of Israel that declared independence in 1988 but is not recognized by all nations as a sovereign country, recorded its hottest temperature in history on August 7, 2010, when the temperature hit 51.4°C (124.5°F) at Kibbutz Almog (also called Qalya or Kalya) in the Jordan Valley. The previous record for this portion of Israel was set on June 22, 1942, at the same location.

All-time national heat records were missed by 1°C or less in many other nations this summer, including the Azores, Morocco, Estonia, and Latvia.

National cold records set in 2010
No nations set record for their coldest temperature in history in 2010. I regret reporting earlier this year that Guinea had done so. Guinea actually had its coldest temperature in history last year, on January 9, 2009, when the mercury hit 1.4°C (34.5°F) at Mali-ville in the Labe region.

Extensive credit for researching these records goes to weather records researcher Maximiliano Herrera, who maintains a comprehensive set of extreme temperature records on his web site. I also thank I thank Christopher C. Burt and Howard Rainford for their assistance identifying this year's new extreme temperature records.

Commentary
The period January - October was the warmest such 10-month period in the planet's history, and temperatures over Earth's land regions were at record highs in May, June, and July, according to the National Climatic Data Center. It is not a surprise that many all-time extreme heat records are being shattered when the planet as a whole is so warm. Global warming "loads the dice" to favor extreme heat events unprecedented in recorded history. In fact, it may be more appropriate to say that global warming adds more spots on the dice--it used to be possible to roll no higher than double sixes, and now it is possible to roll a thirteen.

I'll have a new post on Wednesday, when I plan to discuss how La Niña may affect the coming winter in North America.

Jeff Masters

Heat

Updated: 12:15 PM GMT on April 25, 2011

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Colombia rainy season floods kill 136

By: JeffMasters, 2:01 PM GMT on November 22, 2010

Colombia is experiencing its worst rainy season in at least 30 years, with at least 136 deaths over the past few months and 1.3 million people affected by flooding. Heavy rains in the capital of Bogota on Wednesday brought the Bogota River to its highest level in 30 years, and more rain is in the forecast--the latest forecast from the GFS model (Figure 2)--calls for an additional 3 - 6 inches (75 - 150 mm) in the Bogota region over the coming week.


Figure 1. Satellite-observed rainfall over Colombia during the past two weeks shows a region of 300 - 400 mm (12 - 16 inches) has fallen near Bogota. Image credit: Navy Research Lab, Monterey.

Colombia's rainy season usually peaks in October, then gradually wanes in November and December. The heavy rains are due to the presence of the Intertropical Convergence Zone, the area encircling the earth near the equator where winds originating in the northern and southern hemispheres come together. When these great wind belts come together (or "converge", thus the name "Convergence Zone"), the converging air is forced upwards, since it has nowhere else to go. The rising air fuels strong thunderstorm updrafts, creating a band of very heavy storms capable of causing heavy flooding rains. This year is a La Niña year, which means there is a large region of colder than average water off the Pacific coast of Colombia. Colder than average water off the Pacific coast enhances rainfall over Colombia, and this year's moderate-strength La Niña is largely to blame for Colombia's deadly rainy season.


Figure 2. Rainfall forecast from the GFS model predicts that Bogota may see another 75 - 150 mm (3 - 6 inches) during the coming week. Image credit: NOAA/CPC.

I'll have a new post on Tuesday.

Jeff Masters

Flood

Updated: 2:06 PM GMT on November 22, 2010

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Globe has 3rd or 8th warmest October on record; year-to-date period warmest on record

By: JeffMasters, 2:20 PM GMT on November 19, 2010

October 2010 was the globe's eighth warmest October on record, according to the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC). NASA's Goddard Institute for Space Studies rated October 2010 the third warmest October on record. Both NOAA and NASA rated the year-to-date period, January - October, as the warmest such period on record. October 2010 global ocean temperatures were the 10th warmest on record, and land temperatures were the 6th warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 7th or 2nd warmest on record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH), respectively. UAH rated the year-to-date period, January-October, as the 2nd warmest such period in the satellite data record, behind 1998.

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


Figure 1. Departure of temperature from average for October 2010. Image credit: National Climatic Data Center (NCDC)

Eleventh warmest October on record for the U.S.
For the contiguous U.S., it was the 11th warmest October in the 116-year record, according to the National Climatic Data Center. The year-to-date period, January to October, was the 19th warmest such period on record. Two states had a top-ten warmest October on record--Wyoming and Montana. No states were colder than average.

U.S. precipitation
For the contiguous U.S., October 2010 was the 39th driest on record. Florida had its driest October in the 116-year record, and two other states had top-ten driest Octobers--Missouri and Texas. Nevada had its wettest October on record, and five other states had a top-ten wettest October--New York, Vermont, New Hampshire, Maine, and California.

La Niña in the "moderate" category
The equatorial Eastern Pacific Ocean is currently experiencing moderate La Niña conditions. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", were 1.3°C below average during the first two weeks of November, according to NOAA. The Australian Bureau of Meteorology put this number at 1.23°C below average (as of November 14.) Moderate La Niña conditions are defined as occurring when this number is 1.0°C - 1.5°C below average. Temperatures colder than 1.5°C below average qualify as strong La Niña conditions. NOAA is maintaining its La Niña advisory, and expects La Niña conditions to last through the coming winter into spring.

Both El Niño and La Niña events have major impacts on regional and global weather patterns. La Niña typically causes warm, dry winters over the southern portion of the U.S., with cooler and wetter than average conditions over the Pacific Northwest. The Ohio and Mississippi Valleys states typically have wetter winters than usual during La Niña events. I'll have a full analysis of what La Niña might mean for the coming U.S. winter in a post next week.


Figure 2. Departure of surface temperature from average for the first half of November for the Arctic. Record low sea ice extent during this period has led to three "hot spots" with temperatures up to 12°C (22°F) above average where the sea ice loss was greatest. This unusual warmth is likely to have significant impacts on weather patterns across much of the Northern Hemisphere during the coming months. As I discussed in my post The climate is changing: the Arctic Dipole emerges last December, Francis et al. (2009) found that during 1979 - 2006, years that had unusually low summertime Arctic sea ice had a 10 - 20% reduction in the temperature difference between the Equator and North Pole. This resulted in a weaker jet stream with slower winds that lasted a full six months, through fall and winter. The weaker jet caused a weaker Aleutian Low and Icelandic Low during the winter, resulting in a more negative North Atlantic Oscillation (NAO). This pattern typically brings exceptionally cold and snowy winters to eastern North America and Europe. The winter of 2009 - 2010 saw the most negative NAO since record keeping began in 1950, which resulted in an upside-down winter in North America--unprecedented snowstorms and the coldest winter in 25 years in the U.S., and the warmest winter on record in Canada. The unusual negative NAO conditions may have been due, in part, to the unusually high Arctic sea ice loss the previous summer (3rd greatest on record.) The latest GFS forecast predicts that the NAO will go strongly negative for the remainder of November, resulting in a major cold blast for the Eastern U.S. and Western Europe. Image credit: NOAA/ESRL.

October 2010 Arctic sea ice extent 3rd lowest on record
Arctic sea ice extent in October 2010 was the third lowest in the 31-year satellite record behind 2007 and 2009, according to the National Snow and Ice Data Center. Sea ice extent as of today (November 19) is the lowest on record for this time of year, according to ice extent imagery at the University of Bremen. Ice volume in October was the lowest on record, according to University of Washington Polar Ice Center.

I'll have a new post on Monday.

Jeff Masters

Climate Summaries

Updated: 2:32 PM GMT on November 19, 2010

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Deadly late-season Atlantic hurricanes growing more frequent

By: JeffMasters, 1:40 PM GMT on November 17, 2010

What may be the final tropical disturbance in the Atlantic (94L) has fizzled, due to dry air and increasing wind shear, and there's an excellent chance that this will be final "Invest" of 2010 in the Caribbean. The 2-week wind shear forecast from the GFS model is showing a dramatic increase in wind shear over the Caribbean in the coming weeks, which should put an end to the Caribbean hurricane season. However, it's been another remarkably active November in the tropics this year. The formation of Hurricane Tomas this month marks the fourth consecutive year in the Atlantic with a hurricane occurring November 1 or later. We had Category 1 Hurricane Noel in 2007, Category 4 Hurricane Paloma in 2008, Category 2 Hurricane Ida in 2009, and now Category 2 Tomas in 2010. This is the first time since beginning of reliable hurricane records in 1851 that there have been four consecutive years with a late-season November or December hurricane in the Atlantic. The previous record was three straight years, set in 1984 - 1986. It used to be that late-season hurricanes were a relative rarity--in the 140-year period from 1851 - 1990, only 30 hurricanes existed in the Atlantic on or after November 1, an average of one late-season hurricane every five years. Only four major Category 3 or stronger late-season hurricanes occurred in those 140 years, and only three Caribbean hurricanes. But in the past twenty years, late-season hurricanes have become 3.5 times more frequent--there have been fifteen late-season hurricanes, and five of those occurred in the Caribbean. Three of these were major hurricanes, and were the three strongest late-season hurricanes on record--Lenny of 1999 (155 mph winds), Paloma of 2008 (145 mph winds), and Michelle of 2001 (140 mph winds). Of course, the number of storms we are talking about is small, and one cannot say anything scientifically significant about late-season Atlantic tropical cyclone numbers, unless we include storms from late October as well. This was done, though, by Dr. Jim Kossin of the University of Wisconsin, who published a 2008 paper in Geophysical Research Letters titled, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is an "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high". The recent increase in powerful and deadly November hurricanes would seem to support this conclusion.


Figure 1. Damage on St. Lucia from Hurricane Tomas. Image credit: St. Lucia Star.

Deadly late-season Atlantic tropical cyclones are growing more frequent
In the 500+ years people have been encountering hurricanes in the Atlantic and recording these encounters, we are sure of only twenty November and December storms that have caused loss of life. If we restrict our time window to the past 70 years, when we have a fairly reliable data base of hurricane mortality thanks to the yearly storm summaries published in Monthly Weather Review, we find only ten late-season storms that killed people. Of those ten, seven occurred in the past twenty years, including the second deadliest late-season tropical cyclone on record, Hurricane Gordon of 1994, which killed 1145 people on Haiti. Only the Great Cuba Hurricane of 1932, which killed 3107 people in Cuba, the Cayman Islands, and the Bahamas, was a deadlier late-season tropical cyclone. Hurricane Tomas ranks as the 6th deadliest late-season hurricane since 1851 in the Atlantic. The storm left 30 dead or missing on Haiti, at least nine dead on St.Lucia, two on Curacao, and one in the Virgin Islands. The storm has caused hundreds more indirect cholera deaths in Haiti, by spreading contaminated water.


Figure 2. Number of days a named storm existed in the Atlantic during November and December between 1950 and 2010. Years when an El Niño event occurred are not included, in order to make the plot smoother (El Niño events tend to dampen Atlantic hurricane activity during all portions of the season.) There has been a general increase in late-season tropical cyclone activity over the Atlantic in recent decades.

The increase in deadly late-season storms in the past twenty years is primarily a Caribbean phenomena. Only two deadly late season hurricanes have affected the U.S. in the past century: Hurricane Kate of 1985, which killed five in Florida, and the 1925 Florida Hurricane, which hit southwest Florida as a Category 1 hurricane on December 1. This remarkable storm was the latest landfalling hurricane in U.S. history, and killed 60 people.

Resources
Kossin, J., 2008, "Is the North Atlantic hurricane season getting longer?", Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

A list of the 20 deadly late-season tropical cyclones: http://www.wunderground.com/hurricane/deadly_nove mber.asp

My blog post, Is the Atlantic hurricane season getting longer?

Next post
I'll have a new post on Friday.

Help support Portlight.org's efforts to bring some Christmas cheer to the kids of Haiti, by donating to their Christmas in Haiti campaign.

Jeff Masters

Climate Change Hurricane

Updated: 3:21 PM GMT on August 18, 2011

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Record quiet tropical cyclone activity in the Pacific

By: JeffMasters, 1:37 PM GMT on November 16, 2010

An area of disturbed weather (Invest 94L) in the southern Caribbean a few hundred miles east of the coast of Nicaragua has lost most of its heavy thunderstorm activity, thanks to dry air at middle levels of the atmosphere. Satellite images show just a few clumps of heavy thunderstorms, and no sign of a surface circulation. Water vapor satellite images show a large amount of dry air lies to the north over the northern Caribbean, which is greatly hampering development. NHC is giving 94L just a 20% chance of developing into a tropical depression by Thursday. Wind shear as analyzed by the University of Wisconsin CIMSS group is a moderate 10 - 15 knots, but the dry air surrounding 94L is probably too great too allow development. 94L may bring heavy rains to Honduras on Wednesday, and Belize on Thursday.


Figure 1. Morning satellite image of 94L.

A record quiet typhoon season
While the Atlantic has had its third busiest season on record this year, it has been a record quiet year for tropical cyclones in both the Eastern and Western Pacific. In the Western Pacific, it is currently the quietest typhoon season on record, according to statistics computed by forecaster Paul Stanko at the NWS office on Guam. On average, by this point in the season, there should have been 24.5 named storms, 16 typhoons, and 4 supertyphoons (storms with 150+ mph winds.) So far in 2010, there have been just 14 named storms, 8 typhoons, and 1 supertyphoon. The record lows for the Western Pacific (since 1951) are 18 named storms, 9 typhoons, and 0 supertyphoons. We have a good chance of beating or tying the records for fewest named storms and fewest typhoons, since there are no current threat areas, and none of the models is predicting tropical cyclone development over the next ten days.

A record quiet Eastern Pacific hurricane season
In the Eastern Pacific, it has also been a record-quiet season. On average, the Eastern Pacific has 15 named storms, 8 hurricanes, and 3 intense hurricanes in a season. So far in 2010, there have been 7 named storms, 3 hurricanes, and 2 intense hurricanes. The record quietest season since 1966 was the year 1977, when the Eastern Pacific had 8 named storms, 4 hurricanes, and 0 intense hurricanes. There is a good chance that the 2010 Eastern Pacific hurricane season is over, since we are already into mid-November, and November storms are quite rare in the Eastern Pacific. La Niña is largely responsible to the quiet Eastern Pacific hurricane season, due in part to the cool sea surface temperatures it brought. La Niña also commonly causes less active Western Pacific typhoon seasons, since the warmest waters there shift closer to Asia, reducing the amount of time storms have over water. Still, it is quite remarkable that both of these ocean basins are having record quiet seasons in the same year--there is no historical precedent for such an occurrence.

I'll have an update Wednesday morning.

Jeff Masters

Hurricane

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Little change to Caribbean disturbance 94L

By: JeffMasters, 2:54 PM GMT on November 15, 2010

An area of disturbed weather (Invest 94L) in the southern Caribbean between Colombia and Nicaragua has seen a modest increase in thunderstorm activity this morning, but is battling dry air, and the odds are against the system becoming Tropical Storm Virginie. Satellite images show that 94L has a limited amount of heavy thunderstorms, but the activity is increasing, and a low-level circulation is getting better defined. Water vapor satellite images show a large amount of dry air lies to the north over the northern Caribbean, and this dry air is slowing development. SSTs are warm, 29°C, and wind shear as analyzed by the University of Wisconsin CIMSS group is a moderate 10 - 15 knots.


Figure 1. Morning satellite image of 94L.

Forecast for 94L
The latest SHIPS model forecast predicts that wind shear will remain in the moderate range, 10 - 20 knots, for the next five days. The modest shear and warm SSTs may allow for some slow organization of 94L over the next few days, if the storm can wall off the dry air at mid-levels that has been interfering with development. The models predict that the steering currents in the southern Caribbean will keep 94L moving generally west-northwestward at about 5 - 10 mph for the next three days, which would bring the storm ashore over Nicaragua or northeast Honduras on Wednesday. The models are not showing much development of 94L, and NHC is giving the system just a 20% chance of developing into a tropical depression by Wednesday. I'd put the odds higher, at 30%. The Hurricane Hunter mission into 94L scheduled for today has been canceled, but is slated to go on Tuesday afternoon. At this time, it appears that 94L will stay confined to the Caribbean, and will not be drawn northwards across Cuba towards Florida and the Bahamas.

I'll have an update Tuesday.

Jeff Masters

Hurricane

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Caribbean disturbance 94L slowly organizing

By: JeffMasters, 2:29 PM GMT on November 14, 2010

An area of disturbed weather (Invest 94L) in the southern Caribbean between Colombia and Nicaragua has seen a slow increase in thunderstorm activity and organization this morning, and has the potential to develop into a tropical depression on Monday or Tuesday. Satellite images show that 94L has a modest amount of heavy thunderstorms, and the activity is showing signs of organization, with a large curved band to the west, and a bit of upper-level outflow to the north and west. Water vapor satellite images show a large amount of dry air lies to the north over the northern Caribbean, and this dry air may be slowing development. SSTs are warm, 29°C, and wind shear as analyzed by the University of Wisconsin CIMSS group is a moderate 10 - 15 knots. There is no sign of a closed circulation on satellite imagery this morning.


Figure 1. Morning satellite image of 94L.

Forecast for 94L
The latest SHIPS model forecast predicts that wind shear will remain in the moderate range, 10 - 20 knots, for the next five days. The modest shear, warm SSTs, and relatively moist atmosphere should allow for some slow organization of 94L until landfall. The models predict that the steering currents in the southern Caribbean will keep 94L moving generally west-northwestward at about 5 mph for the next five days, which would bring the storm ashore over Nicaragua or northeast Honduras as early as Tuesday night. Both the GFS and NOGAPS models show some modest development of 94L, and NHC is giving the system a 40% chance of developing into a tropical depression by Tuesday. The Hurricane Hunters are on call to investigate 94L on Monday afternoon. At this time, it appears that 94L will stay confined to the Caribbean, and will not by drawn northwards across Cuba towards Florida and the Bahamas.

I'll have an update Monday.

Jeff Masters

Hurricane

Updated: 3:19 AM GMT on November 15, 2010

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Little change to Caribbean disturbance 94L

By: JeffMasters, 3:10 PM GMT on November 13, 2010

An area of disturbed weather (Invest 94L) in the southern Caribbean off the coast of Colombia has changed little this morning, but has the potential to develop into a tropical depression on Monday or Tuesday. Satellite images show that 94L has a limited amount of heavy thunderstorms, but the activity is showing signs of organization, with several curved bands trying to form, and a bit of upper-level outflow to the north and west. Water vapor satellite images show a large amount of dry air lies to the north over the northern Caribbean, and this dry air may be slowing development. SSTs are warm, 29°C, and wind shear as analyzed by the University of Wisconsin CIMSS group is a moderate 10 - 15 knots. An ASCAT pass from last night showed 94L had a nearly complete surface circulation, but there is no sign of a closed circulation on satellite imagery this morning.


Figure 1. Morning satellite image of 94L.

Forecast for 94L
The latest SHIPS model forecast predicts that wind shear will remain in the moderate range, 10 - 20 knots, through Monday morning, then rise to the high range, 20 - 25 knots, Tuesday through Thursday next week. The modest shear, warm SSTs, and relatively moist atmosphere should allow for some slow organization of 94L through Monday. The models predict that the steering currents in the southern Caribbean will keep 94L moving generally west-northwestward at about 5 mph for the next five days, which would bring the storm ashore over Nicaragua or northeast Honduras as early as Tuesday night. Both the GFS and NOGAPS models show some modest development of 94L, and NHC is giving the system a 40% chance of developing into a tropical depression by Monday. The Hurricane Hunters are on call to investigate 94L on Monday afternoon. At this time, it appears that 94L will stay confined to the Caribbean, and will not by drawn northwards across Cuba towards Florida and the Bahamas.

I'll have an update Sunday by noon EST.

Jeff Masters

Hurricane

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Caribbean disturbance 94L may develop early next week

By: JeffMasters, 8:11 PM GMT on November 12, 2010

An area of disturbed weather (Invest 94L) has developed in the southern Caribbean off the coast of Colombia, and has the potential to develop into a tropical depression early next week. Satellite images show that 94L has a limited amount of heavy thunderstorms, but the activity is showing signs of organization, with several curved bands developing on the west side of 94L's center. Water vapor satellite images show a large amount of dry air lies to the north over the northern Caribbean, and this dry air may slow down development to a small degree. SSTs are warm, 29°C, and wind shear as analyzed by the University of Wisconsin CIMSS group is a moderate 10 - 15 knots.


Figure 1. Afternoon satellite image of 94L.

Forecast for 94L
The latest SHIPS model forecast predicts that wind shear will remain in the moderate range, 10 - 20 knots, through Sunday, then rise to the high range, 20 - 30 knots, Monday through Wednesday next week. The modest shear, warm SSTs, and relatively moist atmosphere should allow for some slow organization of 94L as it moves slowly westwards at 5 mph over the next two days. The models predict that the steering currents in the southern Caribbean will keep 94L moving generally westwards at about 5 mph for the next five days, which would bring the storm ashore over Nicaragua or northeast Honduras on Wednesday. Both the GFS and NOGAPS models show some modest development of 94L, and NHC is giving the system a 30% chance of developing into a tropical depression by Sunday. The Hurricane Hunters are on call to investigate 94L on Monday afternoon. At this time, it appears that 94L will only be a concern for Central America. I give 94L a 50% chance of eventually becoming Tropical Storm Virginie.

I'll have an update Saturday by 1pm EDT.

Jeff Masters

Hurricane

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Is the Atlantic hurricane season getting longer?

By: JeffMasters, 1:35 PM GMT on November 11, 2010

It seems like there have been an unusual number of early and late season tropical storms and hurricanes in the Atlantic in recent years. In 2008, we had four named storms in July, and the second most powerful November hurricane on record. Both 2007 and 2005 had rare December storms, and 2003 featured Tropical Storm Anna, the first April tropical storm ever recorded. This year, Hurricane Tomas made 2010 the fourth straight year with a November hurricane, something that has never occurred in the Atlantic since accurate records began in 1851. The latest runs of the GFS and NOGAPS models are suggesting the possibility that we will have Tropical Storm Virginie in the Caribbean between Colombia and Nicaragua a week from now. Is hurricane season getting longer? Dr. Jim Kossin of the University of Wisconsin published a 2008 paper in Geophysical Research Letters, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high".


Figure 1. Observed sea surface temperature (SST) trends during the official North Atlantic hurricane season (June-November) for the period 1950-2007. Units are °C per century. The dashed rectangle denotes the tropical storm formation region south of 30° North latitude and east of 75° West longitude. Data are from the NOAA Extended Reconstructed Sea Surface Temperature V3 product [Smith et al., 2008]. Image credit: Kossin, J., 2008, "Is the North Atlantic hurricane season getting longer?", Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

Methods
Dr. Kossin utilized the "best track" database of Atlantic tropical cyclone activity going back to 1851. However, since lack of satellite and aircraft reconnaissance data before 1950 makes the early part of this record suspect, he limited his analysis to the period from 1950 onward. The era of best data--the satellite era beginning in 1980--was also looked at separately, to ensure the highest possible data quality. The area studied was only a portion of the Atlantic--the tropical storm formation region south of 30° North latitude and east of 75° West longitude. This region has shown considerable warming of the Sea Surface Temperatures (SSTs) since 1950, in excess of 1°F (0.6°C) (Figure 1). A statistical method called "quantile regression" was employed. The method looked at how certain thresholds that mark the beginning and end of hurricane season have changed over the years. For example, the date where 5% of all tropical storms form earlier than that date, was called the 0.05 quantile, and the date where 5% of all tropical storms form later than that date, was called the 0.95 quantile. Kossin was able to show that the date of the 0.05 quantile got steadily earlier and the date of the 0.95 quantile steadily got later since 1950. Hurricane season for both the period 1950-present and 1980-present got longer by 5 to 10 days per decade.


Figure 2. Trends in tropical storm formation dates, in the region south of 30° North latitude and east of 75° West longitude, at the 0.05.0.95 quantiles. Trends are based on the periods (left) 1950-2007, and (right) 1980-2007. The dates (month/year) associated with the 0.05, 0.25, 0.50, 0.75, and 0.95 quantiles for each period are shown on the top axis (these threshold dates are based on the full sample for each period). Shading denotes the 90% confidence interval. Image credit: Kossin, J., 2008, "Is the North Atlantic hurricane season getting longer?", Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

Relationship with Sea Surface Temperature
The broadening of the Atlantic hurricane season found was strongly dependent upon Sea Surface Temperatures. Both the onset and end of hurricane season shifted by 20 days per degree C of warming of the SST. With global warming projected to increase tropical Atlantic SSTs 1-2°C by the end of the century, can we then expect a 40-80 day increase in the length of hurricane season? Dr. Kossin doesn't explore this possibility, and doesn't blame the observed increase in the length of the season on human-caused global warming of the oceans. There is reason to believe that future warming of the Atlantic SSTs won't necessarily broaden the area over which tropical storms will form, though. Papers by Henderson-Sellers et al. (1998) and Knutson et al. (2008) theorize that as SSTs warm, the lowest temperature at which tropical storms can form will also increase. The current minimum temperature of 26.5°C (80°F) may increase to 28.5°C for a 2°C warming of Atlantic SSTs. Johnson and Xie (2010) have found observational evidence that the lowest temperature at which tropical storms can form has indeed been increasing at about 0.1°C per decade in the Atlantic, in line with climate model predictions.

References
Henderson-Sellers, A., et al., 1998, "Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment", Bull. Am. Meteorol. Soc. 79, 19–38.

Johnson, N.C., and S.P. Xie, 2010, "Changes in the sea surface temperature threshold for tropical convection", Nature Geoscience doi:10.1038/ngeo1008

Knutson, T.R., J.J. Sirutis, S.T. Garner, G.A. Vecchi, and I.M. Held, 2008, Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions", Nature Geoscience 1, 359 - 364 (2008), doi:10.1038/ngeo202

Kossin, J., 2008, "Is the North Atlantic hurricane season getting longer?", Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

Jeff Masters

Climate Change Hurricane

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Caribbean disturbance 93L no threat; remembering the Edmund Fitzgerald storm

By: JeffMasters, 1:31 PM GMT on November 10, 2010

An area of disturbed weather (Invest 93L) near Puerto Rico and the Virgin Islands is drifting northwards. The heavy thunderstorm activity associated with 93L is rather limited, due in part to some surrounding dry air. Wind shear is a moderate 10 - 15 knots and SSTs are very warm, 29°C, but 93L is headed into a region of very high wind shear, and does not have time to develop. None of the reliable global forecast models for predicting tropical cyclone formation (GFS, NOGAPS, ECMWF, and UKMET) are developing 93L into a tropical depression over the coming week, and NHC is giving 93L a 10% chance of developing by Friday.

The GFS and NOGAPS models predict a strong tropical disturbance will form in the southern Caribbean off the coast of Colombia 6 - 7 days from now, and move west-northwest towards Nicaragua.


Figure 1. Rainfall totals for Puerto Rico and the Virgin Islands from Invest 93L.

35th anniversary of the "Edmund Fitzgerald" storm
Thirty five years ago today, on November 10, 1975, one of the strongest storms in Great Lakes history sank the ore carrier Edmund Fitzgerald on Lake Superior, with the loss of all 29 men aboard. Our Weather Extremes blogger Christopher C. Burt has a look back at this date in weather history, which also features four other remarkable record-setting storms: the 1911 Great Cold Front, the 1913 "White Hurricane", the 1940 Armistice Day Blizzard, and the 1998 Super Cyclone.


Figure 2. The S.S. Edmund Fitzgerald in calmer waters. Photo from NOAA.

I'll have a new post Thursday morning.

Jeff Masters

Hurricane

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Indonesian volcano may cut President's visit short

By: JeffMasters, 3:01 PM GMT on November 09, 2010

President Obama is in Jakarta, Indonesia, but that nation's most active volcano--Mount Merapi on Java--is spewing enough ash to potentially cut the President's visit short. Merapi (literally "Mountain of Fire" in Javanese) has been erupting since late October, and the mountain's pyroclastic flows and ash have been blamed for the deaths of over 150 Indonesians since the eruption began. The capital city of Jakarta lies about 250 miles west-northwest of Merapi, and received ash from the volcano over the weekend. At Jakarta's Soekarno-Hatta Airport, airlines canceled 36 flights on Saturday, and an additional 50 flights on Sunday. The airport handles about 900 flights per day. The Indonesian Disaster Management Office reported that volcanic ash from Merapi fell in Jakarta and some nearby areas such as Bogor and Puncak on Saturday night, but only in very light falls. No flights were canceled yesterday, as the ash cloud remained about 50 miles to the south of the city.


Figure 1. Signs of the eruption at Mount Merapi managed to puncture the persistent cloud cover over Java on November 5, 2010. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this natural-color image the same day. The volcano's plume formed a V shape, fanning out to the west from the summit and casting shadows on the surrounding clouds below. According to the Volcanic Ash Advisory Center in Darwin, Australia, the ash plume rose to at least 55,000 feet (16 kilometers) in altitude and stretched 220 miles (350 km) to the west and southwest, as of 12:13 a.m. local time on November 6 (17:13 UTC, Nov 5). Image credit: NASA.

The winds today are blowing from east to west over the Merapi volcano, and are expected to continue this direction for the remainder of the day. According to the latest Volcanic ash advisory from the Darwin, Australia Volcanic Ash Advisory Center (Figure 2), the ash from Merapi extends about 140 miles to the west of the volcano, and is expected to remain just south of Jakarta today. However, the ash cloud is sufficiently close to the city that just a small change in wind direction could bring ash to Jakarta, which might shut down the airport. A run I performed using NOAA's HYSPLIT trajectory model (Figure 2, right side) shows the potential for ash to reach Jakarta if Merapi erupts continuously for 48 hours, beginning at 1am EST this morning. So, the President will have to keep a careful eye on Merapi today in case the ash cloud approaches Jakarta.


Figure 2. Latest volcanic ash advisory from the Darwin, Australia Volcanic Ash Advisory Center (left) predicts that ash from Merapi will stay just south of Jakarta today. NOAA's HYSPLIT trajectory model was run assuming a continuous 48-hour eruption of the volcano began at 1am EST this morning. That model predicts that the ash could from Merapi could come very close to Jakarta by 1am EST on Thursday.

Impact of Merapi on the climate
The amount of sulfur dioxide and ash that Merapi has thrown into the atmosphere thus far has been relatively minor as volcanic eruptions go, and I don't expect Merapi's eruption will cause a noticeable influence on the climate. As I discuss on our Volcanoes and climate web page, major volcanic eruptions in the tropics have, in the past, caused substantial cooling of Earth's climate by injecting large amounts of sulfur dioxide into the stratosphere. The most notable such eruption in recent history was in 1815 by the Indonesian volcano Tambora. The sulfur pumped by this eruption into the stratosphere dimmed sunlight so extensively that global temperatures fell by about 2°F (1°C) for 1 - 2 years afterward. This triggered the famed Year Without a Summer in 1816. Killing frosts and snow storms in May and June 1816 in Eastern Canada and New England caused widespread crop failures, and lake and river ice were observed as far south as Pennsylvania in July and August. Birger Lühr, a volcano researcher at the GFZ in Potsdam, Germany, commented in Der Spiegel magazine that Merapi has a magma reservoir triple the size of Tambora's. Lühr did not expect that the current eruption of Merapi would cause a massive climate-cooling event, but he did caution that the current cone of the volcano lies on top of the ruins of a more ancient crater, evidence that Merapi has had a cataclysmic eruption in the past.

Invest 93L in the Caribbean not currently a threat
An area of disturbed weather (Invest 93L) has developed in the central Caribbean, a few hundred miles south of the Dominican Republic and Puerto Rico. The heavy thunderstorm activity associated with 93L is rather limited, due in part to some dry air to the north. Wind shear is a low 5 - 10 knots and SSTs are very warm, 29°C, so we will have to watch this area for signs of development. None of the reliable global forecast models for predicting tropical cyclone formation (GFS, NOGAPS, ECMWF, and UKMET) are developing 93L into a tropical depression over the coming week, and NHC is giving 93L a 10% chance of developing into a tropical depression by Thursday.


Figure 3. Morning satellite image of Invest 93L.

I'll have a new post Wednesday morning.

Jeff Masters

Volcano

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Is the Atlantic hurricane season of 2010 over?

By: JeffMasters, 1:45 PM GMT on November 08, 2010

Hurricane Tomas is gone, and good riddance to this deadly late-season storm that hit the southern Lesser Antilles and Haiti hard. While Tomas thankfully spared Haiti a flooding catastrophe, it may yet cause heavy loss in that beleaguered nation by worsening their cholera epidemic, which has already claimed over 500 lives. So, with Tomas gone, are we all done for 2010? Or will this third-busiest hurricane season of all-time spawn a twentieth named storm, Tropical Storm Virginie?


Figure 1. The strongest hurricane on record in the Atlantic in November, Hurricane Lenny, takes aim at the Lesser Antilles on November 17, 1999. Image credit: NOAA.

Since the active hurricane period we are in began in 1995, seven of the fifteen years have seen an Atlantic named storm form after November 8: 2007 (Tropical Storm Olga on December 11), 2005 (the "Greek" storms Gamma, Delta, Epsilon, and Zeta), 2004 (Tropical Storm Otto on November 29), 2003 (Odette and Peter in December), 2001 (Hurricane Olga on November 24), 1999 (Hurricane Lenny on November 14), 1998 (Hurricane Nicole on November 24), and 1996 (Hurricane Marco on November 19). Only two of these storms caused loss of life: Tropical Storm Odette of 2007, whose floods killed eight people in the Dominican Republic, and Hurricane Lenny of 1999, which killed fifteen people in the Lesser Antilles. "Wrong-way Lenny" was the only major hurricane of these very late season storms.


Figure 2. Wind shear forecast for November 24, 2010, as predicted by the 2am EDT November 8, 2010 run of the GFS model. The model is predicting low wind shear of less than 4 m/s (about 8 knots, light red colors) over a small region of the Central Caribbean. Very high wind shear in excess of 44 m/s (85 knots, orange colors), associated with the subtropical jet stream, will protect regions north of the Caribbean.

So, judging by the recent history of late season tropical storms, there is about a 50% chance that we are all done this season. The odds of a significant storm that causes loss of life are much lower, less than 15%. The oceans are certainly warm enough to support continued development of tropical cyclones. Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest October on record, according to an analysis I did of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were 0.95°C above average during October, beating the previous record of 0.93°C set in October 2003. Wind shear will also be low enough in the Caribbean to support tropical storm formation over the coming two weeks, according to the latest run of the GFS model (Figure 2.) However, the subtropical jet stream is forecast to slowly edge southwards over the next few weeks, in keeping with its usual seasonal cycle. The Caribbean will gradually see wind shear increase, until only the extreme southern Caribbean near the coast of Panama can support tropical storm formation. Taking all these factors into account, I believe we are all done this hurricane season with dangerous storms capable of causing loss of life. The latest long-range runs of the GFS and ECMWF models don't hint at anything developing over the next seven days, and I give a 30% chance we will see one more inconsequential named storm, which will not cause loss of life if it forms.

I'll have a new post Tuesday or Wednesday morning.

Jeff Masters

Hurricane

Updated: 3:48 PM GMT on November 08, 2010

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Tomas nearly dead; Haiti deals with Tomas' floods

By: JeffMasters, 3:50 PM GMT on November 07, 2010

Tropical Storm Tomas is merging with a cold front over the open Atlantic Ocean and has only a few more hours of life as a tropical cyclone. Despite bringing heavy rains of 4 - 8 inches to highly vulnerable Haiti on Friday, flooding from the storm is only being blamed for eight deaths in the country. Haiti has thankfully avoided a flooding catastrophe, and it certainly could have gone far worse for Haiti. Much weaker storms than Tomas have claimed thousands of lives, and Tomas could easily have done so had it taken a slightly different track. Still, Tomas' passage caused plenty of flooding damage in Haiti. The heavy rains and floods from the storm will also worsen the country's cholera epidemic, which has already claimed over 500 lives. Cholera is a spread via contaminated water, and Tomas' rains will cause a great deal of water contamination. Portlight.org has their mobile kitchen on the scene and is assessing needs. As reported by Rudy Victor in the Portlight.org blog, "Reports coming from the countryside are not good. Thank God its not what we're afraid of, but lots of damage. Leogane a city west of Port-au-Prince is inundated, cities along the extreme southwestern peninsula have suffered great damage by the seas; lots of small fishermen's houses are gone. Dame Marie, Anse d'Hainault, Les Irois, Chambellan, and lots more have been severely damaged by storm surge and raging waves. Gonaives is flooded since last night; luckily there are not reports yet of casualties there. Most people fled to higher ground before the storm. A lot of roads in the south west are destroyed, lots of harvest in the south are lost, and it's another terrible blow for this country, but it appears that there was not a lot of death due to the storm."


Figure 1. Morning afternoon satellite image of Tomas shows that the storm has lost almost all of its heavy thunderstorms, and is now embedded in a cold front that extends northwards to Nova Scotia, Canada. Moisture streaming northwards from Tomas along this front has brought heavy rains in excess of six inches to Nova Scotia over the past few two days.

Jeff Masters

Hurricane

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Tomas spares Haiti, heads out to sea

By: JeffMasters, 4:38 PM GMT on November 06, 2010

Tropical Storm Tomas is over the open Atlantic, headed away from the islands, and is unlikely to trouble any more land areas. Despite bringing heavy rains of 4 - 8 inches to highly vulnerable Haiti yesterday, flooding from the storm is only being blamed for seven deaths thus far, and Haiti has avoided a flooding catastrophe. More Haitians died (12) last weekend from flooding rains of much lesser amounts, so I think part of the credit for the low death toll during Tomas has to go to the preparedness efforts made in advance of the storm. Many people were removed from flood-prone ravines, and flood control ditches and sandbagging efforts helped stymie flood waters. Luck also played a role--had Tomas tracked just ten miles farther west yesterday morning, the eyewall would have avoided disruption from the rugged terrain on Haiti's southwest peninsula. This would have allowed Tomas to strengthen to a Category 2 storm, and the band of very heavy rain to the south of Port-au-Prince would probably have held together and dumped an additional 2 - 4" of rain on the vulnerable earthquake zone.

Tomas plowed through the southeastern Bahamas and Turks and Caicos islands early this morning as a strong tropical storm, and I anticipate that damage in the islands will be minor. Satellite loops show that the storm remains well organized, but clouds from an approaching cold front can be seen to Tomas' north, and the front is expected to catch up to the storm on Sunday and bring a rapid demise for Tomas.


Figure 1. Early afternoon satellite image of Tomas.

Tomas the second most damaging hurricane in St. Lucia history
Prime Minister Stephenson King announced Thursday that damage on the island of St.Lucia was $185 million--five time higher than earlier estimates. This sum is 19% of St. Lucia's GDP, and is the second most expensive hurricane ever for the island. Tomas damaged 10,000 homes and killed 14 people during its rampage over the island last Saturday. St. Lucia received the full brunt of the northern eyewall of Tomas as it intensified, and the St. Lucia weather service reported that sustained winds of 90 - 95 mph affected the island. Power has been restored to 90% of the island and most of the tourist facilities have reopened, however.

Tomas is the strongest hurricane to affect St. Lucia since Category 1 Hurricane Dean of 2007 brought 90 mph winds to the island. Dean killed one person and did $6.4 million in damage--0.5% of the nation's GDP. The island's strongest hurricane since accurate records began in 1851 was Hurricane Allen of 1980, which struck as a Category 3 hurricane with 130 mph winds. Allen killed 18 people on St.Lucia, and caused catastrophic damage of $235 million dollars ($613 million 2010 dollars.) This was 177% of the nation's GDP that year. The deadliest hurricane in St. Lucia history was the Category 5 Great Hurricane of 1780, which killed approximately 700 people. The Great Hurricane of 1780 was the Atlantic's deadliest hurricane of all-time, with 22,000 fatalities, mostly in the Lesser Antilles Islands.


Figure 2. Damage on St. Lucia from Hurricane Tomas. Image credit: St. Lucia Star.

Organizations Active in Haitian Relief Efforts:
Portlight disaster relief has shipped their mobile kitchen to Quisqueya, Haiti, and the kitchen will be ready to feed 500 people per day.
Lambi Fund of Haiti
Haiti Hope Fund
Catholic Relief Services of Haiti

Next update
I'll have an update Sunday morning.

My post on Haiti's hurricane history is now a permanent link in the "Articles of interest" section on our Tropical & Hurricane web page.

Jeff Masters

Hurricane

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Rains abate in Haiti as Tomas weakens

By: JeffMasters, 8:24 PM GMT on November 05, 2010

Data from this afternoon's flight by the Hurricane Hunters shows that Tomas may have weakened to a tropical storm, though NHC is maintaining it as a hurricane in their 5pm advisory. The 3:28pm center fix found that Tomas' pressure had risen to 992 mb, and the top surface winds seen by the SFMR instrument were 64 mph. Highest winds at 10,000 feet were 74 mph, supporting reducing Tomas' status from hurricane to tropical storm--though it is possible that the aircraft did not sample the strongest winds of Tomas. The Gran Piedra, Cuba radar shows fewer echoes than this morning, and satellite loops also reveal a weakened storm, with much less heavy thunderstorm activity near the center. The weakening was probably due to the fact the center of Tomas passed very close to the rugged terrain of Haiti's southwest peninsula, and the rough mountains disrupted the flow into the developing eyewall of the hurricane. Conditions remain favorable for intensification, though, with wind shear a moderate 10 - 20 knots, and SSTs a very warm 29.5°C.


Figure 1. Visible MODIS satellite image taken by NASA's Terra satellite at 11:30am EDT November 5, 2010. image credit: NASA.

Impact on Hispaniola and Cuba
A trough of low pressure over the Eastern U.S. is drawing Tomas northeastward at 12 mph, and this forward speed will gradually increase to 15 mph by early Saturday morning. Tropical storm force winds of 39+ mph extend out about 140 miles to the east, and Tomas is probably bringing tropical storm force winds to the tip of eastern Cuba and Haiti's northwest peninsula at present. Rainfall is the primary concern from Tomas, though, not wind. Satellite estimates (Figure 2) indicate that Tomas dumped up to 4 - 6 inches of rain as of 8am EDT on much of southen Haiti; an additional 1 - 3 inches has probably fallen since then. However, the band of heavy rain to the south of Haiti that appeared poised to give southern Haiti an additional 3 - 6 inches of rain today got disrupted when Tomas' center brushed the mountainous tip of southwest Haiti. Thus, it appears the worst of the rain is over for Haiti. An additional 1 - 2 inches is possible in isolated regions, judging from recent satellite data. Preliminary news reports I've heard from Port-au-Prince indicate that the earthquake zone weathered the storm with no major loss of life. Severe flooding was reported on Haiti's southwest peninsula, with AP video showing 4 feet of water flowing through the streets of Leogane, 20 miles west of Port-au-Prince. It remains to be seen how the rest of Haiti fared, as satellite estimates of rainfall are often low, and do not properly measure the heavier rains that can fall in mountainous regions. A band of heavy rain is over the Dominican Republic this afternoon, and total rainfall amounts approaching ten inches in the mountains regions will likely cause dangerous flooding and mudslides in that country this afternoon and this evening.


Figure 2. Satellite-estimated rain amounts for the 24-hour period ending at 8am EDT Friday, November 5, 2010. Rainfall amounts of 4 - 6 inches (green colors) occurred over Costa Rica, the southwestern peninsula of Haiti, and isolated regions of the Dominican Republic and the rest of Haiti. Image credit: Navy Research Lab, Monterey.

Impact on the Southeast Bahamas and Turks and Caicos Islands
Although Tomas has been weakened by its close encounter with Haiti and now Cuba, the storm is in a favorable environment for re-intensification. I expect Tomas will re-intensify back to 85 mph winds by 2am EDT Saturday, as it passes through the Southeast Bahamas and Turks and Caicos Islands. Once Tomas pushes north of the islands on Sunday, the storm should weaken quickly, as wind shear is expected to rise to a very high 50 knots.

Tomas the second most damaging hurricane in St. Lucia history
Prime Minister Stephenson King announced yesterday that damage on the island of St.Lucia was $185 million--five times higher than earlier estimates. This sum is 19% of St. Lucia's GDP, and is the second most expensive hurricane ever for the island. Tomas damaged 10,000 homes and killed 14 people during its rampage over the island last Saturday. St. Lucia received the full brunt of the northern eyewall of Tomas as it intensified, and the St. Lucia weather service reported that sustained winds of 90 - 95 mph affected the island. Power has been restored to 90% of the island and most of the tourist facilities have reopened, however.

Tomas is the strongest hurricane to affect St. Lucia since Category 1 Hurricane Dean of 2007 brought 90 mph winds to the island. Dean killed one person and did $6.4 million in damage--0.5% of the nation's GDP. The island's strongest hurricane since accurate records began in 1851 was Hurricane Allen of 1980, which struck as a Category 3 hurricane with 130 mph winds. Allen killed 18 people on St.Lucia, and caused catastrophic damage of $235 million dollars ($613 million 2010 dollars.) This was 177% of the nation's GDP that year. The deadliest hurricane in St. Lucia history was the Category 5 Great Hurricane of 1780, which killed approximately 700 people. The Great Hurricane of 1780 was the Atlantic's deadliest hurricane of all-time, with 22,000 fatalities, mostly in the Lesser Antilles Islands.


Figure 3. Damage on St. Lucia from Hurricane Tomas. Image credit: St. Lucia Star.

Organizations Active in Haitian Relief Efforts:
Portlight disaster relief has shipped their mobile kitchen to Quisqueya, Haiti, and the kitchen will be ready to feed 500 people per day.
Lambi Fund of Haiti
Haiti Hope Fund
Catholic Relief Services of Haiti

Next update
I'll have an update Saturday morning.

My post on Haiti's hurricane history is now a permanent link in the "Articles of interest" section on our Tropical & Hurricane web page.

Jeff Masters

Hurricane

Updated: 8:48 PM GMT on November 05, 2010

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Hurricane Tomas lashing Haiti with torrential rains

By: JeffMasters, 1:57 PM GMT on November 05, 2010

Deadly Hurricane Tomas has intensified into a dangerous Category 1 hurricane with 85 mph winds this morning, and is lashing Haiti, eastern Cuba, and the southwestern coast of the Dominican Republic with torrential rains. Observations from the Gran Piedra, Cuba radar show that the eye of Tomas is skirting the tip of the southwestern Peninsula of Haiti, and the winds of the powerful eastern eyewall of the storm are pounding the western end of the peninsula. An Air Force hurricane hunter aircraft just left Tomas, and measured top surface winds of 86 mph at 7:13am EDT. Satellite loops of Tomas show an impressive Central Dense Overcast (CDO) of high cirrus clouds with very cold tops has pushed into the lower stratosphere above Tomas and has flattened out, hiding the surface center from view. An eye is not yet visible on satellite imagery. The latest center fix at 7:08am EDT found that the pressure had risen slightly to 988 mb, which may be a sign that interaction with the mountainous terrain of southwestern Haiti may have caused some disruption of Tomas. However, Tomas should resume intensifying this afternoon now that the center has moved past the southwestern tip of Haiti, as wind shear is a moderate 10 - 20 knots, and SSTs are a very warm 29.5°C.


Figure 1. Rainfall rate for Tomas as observed by the F-17 polar orbiting satellite at 6:42am EDT Friday, November 5, 2010. Heaviest rainfall rates in excess of 1.4 inches per hour (pink colors) were in the west eyewall, and are likely to miss Haiti. However, a long band of intense rain (1/2" - 3/4" per hour) extended to the southwest of Port-au-Prince, and these rains will impact the cities in Haiti most vulnerable to catastrophic flooding, Port-au-Prince and Gonaives. Image credit: Navy Research Lab, Monterey.

Impact on Hispaniola and Cuba
A trough of low pressure over the Eastern U.S. is drawing Tomas northeastward at 9 mph, and this forward speed will gradually increase to 15 mph by early Saturday morning. Hurricane force winds extend outwards only 15 miles to the east of Tomas' center, and only the extreme tips of Haiti's southwest and northwest peninsulas will receive hurricane force winds. Tropical storm force winds of 39+ mph extend out about 140 miles to the east, and Tomas will pass far enough from the Port-au-Prince earthquake zone that winds there will not exceed 30 - 35 mph. However, the northern Haitian city of Gonaives will receive 40 - 45 mph winds this afternoon and this evening, as will the eastern tip of Cuba. Rainfall is the primary concern from Tomas, though, not wind. Satellite estimates (Figure 1) indicate that Tomas has already dumped up to 6 inches of rain on Haiti's southwest peninsula, and 3 inches in the Port-au-Prince earthquake zone. Recent microwave imagery (Figure 2) shows that while the heaviest rains from Tomas lie in the west eyewall and will miss Haiti, a long band of heavy rain with rainfall rates of 1/2" - 3/4" per hour lies to the southwest of Port-au-Prince and Gonaives, the two most vulnerable cities in Haiti to catastrophic flooding. The rain band is lined up to bring the earthquake zone of Haiti an additional 3" - 6" of rain today and tonight, bringing the storm total for Port-au-Prince and the surrounding mountains to 6" - 9". Rains of this magnitude are likely to cause extremely dangerous flooding for the 1.3 million Haitians living in makeshift refugee camps, and may cause heavy loss of life. Also of concern is the rains that will fall in northwestern Haiti, particularly in the highly vulnerable city of Gonaives, where rains from Tropical Storm Jeanne in 2004 killed 3,000 people. A band of heavy rain will also affect the southern Dominican Republic today, and total rainfall amounts approaching ten inches in the mountains near the southwestern coast will likely cause dangerous flooding and mudslides.


Figure 2. Satellite-estimated rain amounts for the 24-hour period ending at 2am EDT Friday, November 5, 2010. Rainfall amounts of up to 6 inches (dark green colors) occurred over Costa Rica and the extreme southwestern tip of Haiti. Image credit: Navy Research Lab, Monterey.

Impact on the Southeast Bahamas and Turks and Caicos Islands
Tomas appears likely to thread the narrow gap of water between Cuba and Haiti, and will likely emerge into the Southeast Bahamas and Turks and Caicos Islands as a Category 1 hurricane. According to the 5am EDT NHC wind radius forecast (Figure 3), tropical storm force winds of 39+ mph should begin in the Inagua Islands by noon today, then spread to the Turks and Caicos Islands by 3pm EDT. A 30-mile wide swath along the center of Tomas' path will receive hurricane force winds of 74+ mph. Once Tomas pushes north of the islands on Sunday, the storm should weaken quickly, as wind shear is expected to rise to a very high 50 knots.


Figure 3. Predicted position and location of Tomas' tropical storm force winds (dark green colors) and hurricane force winds (yellow colors) as predicted in the 5am EDT NHC advisory.

Costa Rica mudslides kill 20
Mudslides killed at least 20 people in Costa Rica yesterday, after heavy rains sent mud rushing over at least five homes in San Antonio de Escazu, a suburb of the nation's capital. A very moist flow of Pacific air been drawn eastwards over Central America over the past three days by Hurricane Tomas, triggering the heavy rains in Costa Rica. This moisture has also been drawn into Hurricane Tomas, and is helping fuel the heavy rains over Haiti. Satellite observations (Figure 2) suggest that up to 6 inches of rain fell over Costa Rica during the 24 hours ending at 2am EDT this morning. Earlier in the week, an additional 2 - 6 inches of rain had fallen over the nation.

Organizations Active in Haitian Relief Efforts:
Portlight disaster relief has shipped their mobile kitchen to Quisqueya, Haiti, and the kitchen will be ready to feed 500 people per day.
Lambi Fund of Haiti
Haiti Hope Fund
Catholic Relief Services of Haiti

Next update
I'll have an update this afternoon.

My post on Haiti's hurricane history is now a permanent link in the "Articles of interest" section on our Tropical & Hurricane web page.

Jeff Masters

Hurricane

Updated: 8:12 PM GMT on November 05, 2010

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Little change to Tomas as it bears down on Haiti

By: JeffMasters, 7:44 PM GMT on November 04, 2010

Tropical Storm Tomas is headed north towards Haiti, and the northernmost spiral bands of the storm have already reached the tip of Haiti's southwestern peninsula, the eastern tip of Jamaica, and eastern Cuba. It appears at this time that the most dangerous flooding rains of 5 - 10 inches will be confined to the southwestern and northwestern peninsulas of Haiti, and that the earthquake zone where 1.3 million people live in makeshift shelters and tents will experience lesser rains that will cause serious but not catastrophic flooding. Satellite loops of Tomas show an average-sized tropical storm with a modest amount of heavy thunderstorm activity and low-level spiral bands. Upper-level outflow is good to the north, fair to the east, and poor elsewhere. Wind shear as diagnosed by the University of Wisconsin CIMSS group is a moderate 10 - 20 knots. The shear is due to strong upper-level winds out of the southwest, and the shear is keeping most of Tomas' heavy thunderstorms pushed over to the northeast side of the storm. The low-level center of circulation has been exposed to view most of the afternoon, the tell-tale sign of a tropical storm struggling with wind shear. The areal coverage and intensity of Tomas' thunderstorms has continued to grow this afternoon, but Tomas' winds and pressure have remained about the same. A 2:31pm center fix by an Air Force hurricane hunter aircraft found a central pressure of 999 mb--several millibars higher than early this morning. Top surface winds of 57 mph were seen with their SFMR instrument. Rainfall amounts as observed by the Metopa polar orbiting satellite at 10:23am were 0.5 - 1.0" per hour in a 100-mile wide region near the center of Tomas (Figure 1.) One odd aspect of Tomas is that the area of low pressure 200 - 300 miles southwest of Tomas has gotten better defined with an steady increase in heavy thunderstorm activity this afternoon. This movement of energy to the southwest is probably responsible for the 3 mb rise in Tomas' pressure over the past three hours. It is possible, but not likely, that Tomas' center could relocate 200 miles to the south-southwest later tonight, resulting in a 12 hour longer period of rainfall for Haiti, eastern Cuba, the Dominican Republic, and Jamaica.


Figure 1. Rainfall rate for Tomas as observed by the Metopa polar orbiting satellite at 10:23am EDT Thursday, November 4, 2010. Heaviest rainfall rates in excess of 0.5 inches per hour (green colors) were confined to a 100-mile wide area near the core of Tomas. Image credit: Navy Research Lab, Monterey.

Track and rainfall forecast for Tomas
A trough of low pressure over the Eastern U.S. is drawing Tomas northward at 7 mph, and this forward speed will gradually increase to 10 mph late tonight. Heavy rains from Tomas will spread over all of Haiti, western portions of the Dominican Republic, and eastern Cuba by tonight. Satellite-based estimates of current rainfall rates from Tomas (Figure 2) yield predictions of 2 - 4 inches of rain falling over an 18-hour period near the core of Tomas. This forecast only uses the current intensity of the storm to come up with a rainfall forecast, and if Tomas intensifies today, rainfall amounts will be higher. Tomas has an elongated band of heavy rains that extend all the way to South America, so I expect that the southwest and northwest peninsulas of Haiti will receive heavy rains until Saturday night or Sunday morning. Taking these factors into account, plus the current track forecast, I expect that the heaviest rains from Tomas will fall over these two peninsulas, and accumulate to 5 - 10 inches. Precipitation amounts over Haiti's earthquake zone and the western Dominican Republic will be 3 - 5 inches, with some isolated areas receiving up to 8 inches. The most severe flooding problems from Tomas will probably be in Haiti's southwestern Peninsula, and in the city of Gonaives in northwest Haiti, where most of the 3,000 deaths from Hurricane Jeanne's rains in 2004 occurred. The NHC rainfall forecast for 1 to 3 inches over Jamaica, 3 to 5 inches over eastern Cuba, the southeastern Bahamas, and the Turks and Caicos Islands looks good.


Figure 2. Predicted rain amounts for the 18-hour period ending at 2am EDT Friday, November 5, 2010, as forecast using satellite-derived measurements of precipitation rates. Image credit: NOAA/NESDIS.


Figure 3. Predicted cumulative rainfall from Tomas as predicted by the 8am EDT (12Z) Thursday, November 4, 2010 run of the GFDL model. The model predicts no rainfall amounts in excess of 8 inches (yellow colors) for Haiti. Image credit: Morris Bender, NOAA/GFDL.

The computer models now agree that the trough of low pressure pulling Tomas northward will be strong enough to pull Tomas well north of the Bahamas, and the storm will not stall out near Hispaniola for many days as was being predicted by many of the models yesterday. Wind shear will rise to the high range, 35 - 60 knots, by Sunday, resulting in a steady weakening of Tomas.

Intensity forecast for Tomas
Tomas continues to have difficulty disentangling itself from an area of low pressure over the southwest Caribbean, and this low is acting to steal moisture from Tomas and distort its circulation. As Tomas pulls away from this low, these effects will lessen, and Tomas may be able to intensify into a minimal Category 1 hurricane before reaching the Turks and Caicos Islands and southeastern Bahamas. Wind shear as predicted by the SHIPS model will remain in the low to moderate range, 5 - 15 knots, through Saturday afternoon, which should allow for some modest intensification. NHC is giving Tomas a 43% chance of reaching hurricane strength by Friday evening.

Comparison with Hurricane Ernesto of 2006
Tomas's current position and intensity are similar to that of Tropical Storm Ernesto of 2006. Ernesto was a small to moderate-sized tropical storm with 50 mph winds when it hit the southwestern tip of Haiti on August 27. According to Wikipedia, In Haiti, the storm caused heavy rainfall of over 11 inches (300 mm) and strong winds, causing flooding and destroying 13 homes on the island of La Gonave. In Port-au-Prince, rainfall severely damaged a bridge, isolating the southern portion of the region. Across the country, 59 homes were damaged, of which six destroyed, and a total of five deaths were reported..

Tomas is a larger and wetter storm than Ernesto , and I expect that Tomas' rains in Haiti will be about 25% greater than Ernesto's. Since Haiti is more vulnerable to disasters because of the floods of 2008 and the 2010 earthquake, the rains from Tomas will cause more death and destruction than Ernesto did, but I don't expect a catastrophe with many hundreds of deaths in Haiti's earthquake zone. Such a catastrophe is possible in southwest or northwest Haiti, however.


Figure 4. Track of Hurricane Ernesto in 2006.

Organizations Active in Haitian Relief Efforts:
Portlight disaster relief
Lambi Fund of Haiti
Haiti Hope Fund
Catholic Relief Services of Haiti

Next update
I'll have an update Friday morning.

Yesterday's post on Haiti's hurricane history is now a permanent link in the "Articles of interest" section on our Tropical & Hurricane web page.

Jeff Masters

Hurricane

Updated: 8:12 PM GMT on November 04, 2010

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Tomas' rains reach Haiti and Jamaica

By: JeffMasters, 2:11 PM GMT on November 04, 2010

Tropical Storm Tomas is headed north towards Haiti, and the northernmost spiral bands of the storm have already reached the tip of Haiti's southwestern peninsula and the eastern tip of Jamaica. It appears at this time that the most dangerous flooding rains of 5 - 10 inches will be confined to the southwestern peninsula of Haiti, and that the earthquake zone where 1.3 million people live in makeshift shelters and tents will experience lesser rains that will cause serious but not catastrophic flooding. Satellite loops of Tomas show an average-sized tropical storm with a modest amount of heavy thunderstorm activity and low-level spiral bands. Upper-level outflow is good to the north, fair to the east, and poor elsewhere. Wind shear as diagnosed by the University of Wisconsin CIMSS group is a moderate 10 - 20 knots. The shear is due to strong upper-level winds out of the southwest, and the shear is keeping most of Tomas' heavy thunderstorms pushed over to the northeast side of the storm. The areal coverage and intensity of the thunderstorms has grown this morning. An Air Force hurricane hunter is in Tomas this morning, and reported top surface winds of 52 mph at 9am EDT this morning with their SFMR instrument. Rainfall amounts as observed by the F-16 polar orbiting satellite at 8:05am were 0.5 - 1.0" per hour in a 100-mile wide region near the center of Tomas (Figure 1.)


Figure 1. Rainfall rate for Tomas as observed by the F-16 polar orbiting satellite at 8:05am EDT Thursday, November 4, 2010. Heaviest rainfall rates in excess of 0.5 inches per hour (green colors) were confined to a 100-mile wide area near the core of Tomas. Image credit: Navy Research Lab, Monterey.

Track and rainfall forecast for Tomas
A trough of low pressure over the Eastern U.S. is drawing Tomas north-northwestward at 6 mph, and this forward speed will gradually increase to 10 mph late tonight. Heavy rains from Tomas will spread over all of Haiti's southwestern peninsula and eastern Jamaica this afternoon, then move into the rest of Haiti and western portions of the Dominican Republic by tonight. Satellite-based estimates of current rainfall rates from Tomas (Figure 2) yield predictions of 4 - 6 inches of rain falling over an 18-hour period near the core of Tomas, and we can expect that the heaviest rains from Tomas will fall over Haiti's southwest peninsula, and accumulate to 5 - 10 inches. According to this rainfall forecast, precipitation amounts over Haiti's earthquake zone will be much lower, perhaps just 2 - 4 inches. However, this forecast only uses the current intensity of the storm to come up with a rainfall forecast, and if Tomas intensifies today, rainfall amounts will be higher. The latest rainfall forecast from the GFDL model (Figure 3) agrees that it will primarily be Haiti's southwest peninsula that will experience dangerous rains in the 4 - 8 inch range, and that Haiti's earthquake zone is likely to see lower amounts of 1 - 4 inches. Rains of 1 - 4 inches in the earthquake zone are still capable of causing life-threatening flooding. Rains of similar magnitude killed 12 people there last weekend, and the soils are still saturated. However, potentially catastrophic flooding from Tomas is likely to be limited to Haiti's southwest peninsula, and we are not likely to see a massive flooding catastrophe killing hundreds of people in Haiti's earthquake zone. There will probably be some isolated regions of eastern Haiti and the western Dominican Republic that will see heavier rains of 4 - 8 inches; hopefully, the earthquake zone of Haiti will avoid being one of these spots of higher rainfall. I expect general rainfall amounts of 2 - 4 inches over eastern Jamaica and the western Dominican Republic from Tomas, with higher rainfall amounts of 3 - 6 inches likely over eastern Cuba, the Turks and Caicos Islands, southeastern Bahamas, and eastern tip of Cuba.


Figure 2. Predicted rain amounts for the 18-hour period ending at 8pm EDT Thursday, November 4, 2010, as forecast using satellite-derived measurements of precipitation rates. Image credit: NOAA/NESDIS.


Figure 3. Predicted cumulative rainfall from Tomas as predicted by the 2am EDT (06Z) Thursday, November 4, 2010 run of the GFDL model. The model predicts no rainfall amounts in excess of 8 inches (yellow colors) for Haiti. Image credit: Morris Bender, NOAA/GFDL.

The computer models now agree that the trough of low pressure pulling Tomas northward will be strong enough to pull Tomas well north of the Bahamas, and the storm will not stall out near Hispaniola for many days as was being predicted by many of the models yesterday. Wind shear will rise to the high range, 20 - 30 knots, by Sunday, resulting in a steady weakening of Tomas.

Intensity forecast for Tomas
Tomas continues to have difficulty disentangling itself from an area of low pressure over the southwest Caribbean, and this low is acting to distort the circulation of Tomas into a more oval shape and make the circulation tilt with height. Recent satellite imagery suggests that the circulation of Tomas is becoming more circular and vertically aligned, though, and Tomas may be able to intensify into a minimal Category 1 hurricane before land interaction with Haiti disrupts the storm. Wind shear as predicted by the SHIPS model will remain in the moderate range, 10 - 15 knots, which should allow some modest intensification through Friday afternoon. NHC is giving Tomas a 41% chance of reaching hurricane strength by Friday afternoon.

Organizations Active in Haitian Relief Efforts:
Portlight disaster relief
Lambi Fund of Haiti
Haiti Hope Fund
Catholic Relief Services of Haiti

Next update
I'll have an update later today.

Yesterday's post on Haiti's hurricane history is now a permanent link in the "Articles of interest" section on our Tropical & Hurricane web page.

Jeff Masters

Hurricane

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A weakened Tomas still a grave danger to Haiti

By: JeffMasters, 1:38 PM GMT on November 03, 2010

As this record-breaking third busiest Atlantic hurricane season in history unfolded, I marveled that earthquake-ravaged Haiti managed to dodge significant rain-making tropical storms throughout the peak months of August, September, and October. Cruel fate will not allow Haiti to escape the entire season unscathed, though, as a late-season November storm already proven to be a killer--Tomas--takes aim at Haiti. Tomas has struggled mightily over the past few days, and is now a tropical depression. However, even if it does not reach hurricane strength, Tomas is still likely to bring heavy rains capable of causing disastrous flooding in defenseless Haiti. It doesn't take much rain to cause a flooding disaster in Haiti--ordinary seasonal heavy rains have killed 23 people in southern Haiti over the past month, including twelve people in Port-au-Prince this past weekend. According to the Associated Press, most of last weekend's deaths occurred when surging rivers burst through houses built in ravines. With the soils already saturated from last weekend's rains, the stage is set in Haiti for a significant flooding disaster capable of causing heavy loss of life. I believe it is 30% likely that Tomas will stay far enough west of the Haiti earthquake zone so that rains will be limited to 1 - 4 inches to the region, causing only modest flooding problems and little or no loss of life. More likely (40% chance) is the possibility of major flooding due to 4 - 8 inches of rains. Finally, I expect a 30% chance that heavier rains of 5 - 20 inches over Haiti will cause catastrophic flooding like experienced in 2008's four hurricanes. Potential flooding disasters are not possible just in the earthquake zone, but also in northern Haiti and the southwestern peninsula of Haiti. So, keep praying for the people of Haiti, they need all the help they can get.


Figure 1. Morning satellite image of Tomas.

Tomas struggling
Satellite loops of Tomas show a very disorganized tropical depression, with clumps of heavy thunderstorms scattered about the center in a vaguely cyclonic fashion. However, the thunderstorms are increasing in intensity and areal coverage this morning, and upper-level outflow is now well-established to the north. Given the highly favorable environment for intensification Tomas is in, the current satellite presentation suggests that Tomas is at the beginning of a period of steady intensification that will take it back to tropical storm strength by tonight, and to Category 1 hurricane strength by Friday. A hurricane hunter aircraft will have a better estimate of Tomas' strength by early this afternoon.

Track forecast for Tomas
The ridge of high pressure pushing Tomas to the west has weakened, allowing Tomas to slow down to a forward speed of 4 mph this morning. A trough of low pressure approaching the eastern U.S. has now begun to pull Tomas more to the west-northwest, and a sharper northward turn will develop today, and become a north-northeast motion by Friday. This motion should take Tomas just east of Jamaica and over western Haiti on Friday. NHC is giving Port-au-Prince, Haiti, a 46% chance of receiving tropical storm force winds, and a 5% chance of hurricane force winds. These odds are 45% and 4%, respectively for Kingston, Jamaica, and 19% and 2% for Santo Domingo in the Dominican Republic. Heavy rains from Tomas will begin affecting Jamaica and southwestern Haiti beginning on Thursday afternoon, and will spread to eastern Cuba, the Dominican Republic, and the rest of Haiti by Friday morning. Tomas will probably not be as bad for Jamaica as Tropical Storm Nicole in September, which killed 14 and did $245 million in damage. Nicole's rains lasted three days in Jamaica, and Tomas' rains should last at most 1 1/2 days on the island.

While all of the computer models agree on the motion of Tomas through Friday, there continue to be major differences in forecasts for what happens beginning on Saturday. The trough of low pressure pulling Tomas to the north is expected to lift out, leaving Tomas behind in an area of weak steering currents. The official NHC forecast follows the GFS and ECMWF models, which have been very consistent and reliable predicting the track of Tomas. These models forecast that Tomas will stall several hundred miles north of Haiti, then move slowly eastward. However, the GFDL model stalls Tomas just west of Port-au-Prince Haiti, predicting a days-long period of heavy rains for Haiti. The UKMET and NOGAPS model solutions are also unpleasant for Haiti; these models predict that Tomas will stall over the Turks and Caicos Islands, then drift south over eastern Cuba and western Haiti. The farther north Tomas gets, the higher wind shear will be, and the weaker the storm will get. However, if Tomas stays near the latitude of Hispaniola, wind shear will be low to moderate, and the storm will be able to maintain its strength if the center stays over water. Given recent model trends, I believe a multi-day period of heavy rains that could total twenty inches for eastern Cuba, Haiti, and the western Dominican Republic is at least 30% likely.

Intensity forecast for Tomas
Tomas' struggles to intensify over the past day are difficult to explain scientifically, as all the data we have suggests the storm should have strengthened. Our ability to forecast intensification is limited by the poor availability of data over the oceans, though, and there must be a layer of wind shear or dry air our sensors cannot pick out that is interfering with development. In the absence of any concrete evidence on what is causing Tomas' current troubles, I must continue to forecast intensification over the coming two days. Wind shear as diagnosed by the SHIPS model has dropped to the low range, 5 - 10, and is predicted to stay in the low range for the next three days. The atmosphere is very moist in the Caribbean, as seen on water vapor satellite imagery, and the models predict a very moist atmosphere will surround Tomas for the remainder of the week. With SSTs at a record warm 29.5°C and a very high ocean heat content, there is a substantial danger that Tomas will undergo a period of rapid intensification if has time to build an eyewall. Crucially, the storm has waited too long to begin this process, and it now appears unlikely that Tomas will have time to grow beyond Category 1 hurricane strength before landfall in Haiti on Friday. NHC is giving Tomas a 5% chance of reaching Category 3+ strength, which is a reasonable forecast. With the atmosphere expected to be very moist, it is likely that Tomas will dump very heavy rains of 4 - 8 inches over much of Haiti, even if Tomas strikes as a tropical storm. Rains of this magnitude are capable of causing heavy loss of life due to extreme floods running down Haiti's deforested mountain slopes. Portlight.org is preparing to send their mobile kitchen with enough food to feed 500 people per day, if the threat from Tomas materializes as forecast.

Haiti's hurricane history
In many ways, the hurricane season of 2008 was the cruelest ever experienced in Haiti. Four storms--Fay, Gustav, Hanna, and Ike--dumped heavy rains on the impoverished nation. The rugged hillsides, stripped bare of 98% of their forest cover thanks to deforestation, let flood waters rampage into large areas of the country. Particularly hard-hit was Gonaives, the fourth largest city. According to reliefweb.org, Haiti suffered 793 killed, with 310 missing and another 593 injured. The hurricanes destroyed 22,702 homes and damaged another 84,625. About 800,000 people were affected--8% of Haiti's total population. The flood wiped out 70% of Haiti's crops, resulting in dozens of deaths of children due to malnutrition in the months following the storms. Damage was estimated at over $1 billion, the costliest natural disaster in Haitian history, prior to the 2010 earthquake. The damage amounted to over 5% of the country's $17 billion GDP, a staggering blow for a nation so poor.


Figure 2. The flooded city of Gonaives after Hurricane Hanna, September 3, 2008. Image credit: Lambi Fund of Haiti.

Two thousand and eight was only one of many years hurricane have brought untold misery to Haiti. Hurricane Jeanne of 2004 passed just north of the country as a tropical storm, dumping 13 inches of rains on the nation's northern mountains. The resulting floods killed over 3000 people, mostly in the town of Gonaives. Jeanne ranks as the 12th deadliest hurricane of all time on the list of the 30 most deadly Atlantic hurricanes . Unfortunately for Haiti, its name appears several times on this list. Hurricane Flora killed over 8000 people in 1963, making it the 6th most deadly hurricane ever. An unnamed 1935 storm killed over 2000, and Hurricane Hazel killed over 1000 in 1954. More recently, Hurricane Gordon killed over 1000 Haitians in 1994, and in 1998, Hurricane Georges killed over 400 while destroying 80% of all the crops in the country.

Surprisingly, only six major Category 3 and stronger hurricanes have struck Haiti since 1851. The strongest hurricane to hit Haiti was Hurricane Cleo of 1964, which struck the southwestern peninsula as a Category 4 storm with 150 mph winds, killing 192 people. Haiti's only other Category 4 storm was Hurricane Flora of 1963, which had 145 mph winds when it struck the southwestern peninsula, killing 8000. No Category 5 hurricanes have hit Haiti since 1851. The most recent Category 3 hurricane to hit Haiti was Hurricane David of 1979, which crossed northern Haiti as a Category 3 hurricane with 115 mph winds after hitting the Dominican Republic as a Category 5 hurricane with 170 mph winds. David weakened quickly to a tropical storm after crossing into Haiti, as caused no deaths in the country. The other major hurricanes to strike Haiti were Hurricane Inez of 1966, which hit southern Haiti as a Category 3 hurricane with 115 mph winds, killing 480 people; Hurricane Katie of 1955, which hit near the Haiti/Dominican Republic border with 115 mph winds, killing 7; and Hurricane Five of 1873, which hit the southwestern peninsula with 115 mph winds.


Figure 3.Two of 2008's four tropical cyclones that ravaged Haiti: Tropical Storm Hanna (right) and Hurricane Gustav (left). Image taken at 10:40 am EDT September 1, 2008. Image credit: NASA/GSFC.

Why does Haiti suffer a seemingly disproportionate number of flooding disasters? The answer in that in large part, these are not natural disasters--they are human-caused disasters. Haiti is the poorest nation in the Western Hemisphere. With oil too expensive for the impoverished nation, charcoal from burnt trees has provided 85% or more of the energy in Haiti for decades. As a result, Haiti's 8 million poor have relentlessly hunted and chopped down huge amounts of forest, leaving denuded mountain slopes that rainwater washes down unimpeded. Back in 1980, Haiti still had 25% of its forests, allowing the nation to withstand heavy rain events like 1979's Category 3 Hurricane David without loss of life. But as of 2004, only 1.4% of Haiti's forests remained. Jeanne and Gordon were not even hurricanes--merely strong tropical storms--when they stuck Haiti, but the almost total lack of tree cover contributed to the devastating floods that killed thousands. And it doesn't even take a tropical storm to devastate Haiti--in May of 2004, three days of heavy rains from a tropical disturbance dumped more than 18 inches of rain in the mountains, triggering floods that killed over 2600 people.

What can be done to reduce these human-worsened natural disasters? Education and poverty eradication are critical to improving things. In addition, reforestation efforts and promotion of alternative fuels are needed.

In the past two decades, the U.S. Agency for International Development has planted some 60 million trees, while an estimated 10 to 20 million of these are cut down each year, according to the USAID director in Haiti, David Adams. If you're looking for a promising way to make a charitable donation to help Haitian flood victims, considering supporting the Lambi Fund of Haiti, which is very active in promoting reforestation efforts, use of alternative fuels, and infrastructure improvements at a grass-roots level to help avert future flood disasters.

Organizations Active in Haitian Relief Efforts:
Portlight disaster relief
Lambi Fund of Haiti
Haiti Hope Fund
Catholic Relief Services of Haiti

Next update
I'll have an update later today if there is a significant change with Tomas to report. Otherwise, expect the next update Thursday morning.

Note that the section on Haiti's hurricane history is now a permanent link in the "Articles of interest" section on our Tropical & Hurricane web page.

Jeff Masters

Hurricane

Updated: 3:57 PM GMT on November 03, 2010

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Tomas gradually strengthening; 14 dead in St. Lucia from the storm

By: JeffMasters, 2:58 PM GMT on November 02, 2010

The islands of St. Lucia, Barbados, and St. Vincent and the Grenadines continue to assess damage and clean up after Hurricane Tomas pounded the Lesser Antilles as a strengthening Category 1 hurricane with 90 - 95 mph winds on Saturday. St. Lucia was hardest hit, with fourteen people dead, many more missing, and damage estimated at $100 million--about 10% of the nation's GDP. Damage on neighboring St. Vincent was estimated at $62 million, which is 4% of that nation's GDP. The storm damaged 1,200 houses, and the northern half of the island, where most of the crops are, was badly hit, with no banana trees left standing and the plantain crop wiped out. Banana production employs 60% of the workforce on St. Vincent, and accounts for more than 50% of their exports. Also hard-hit was Barbados, where damage estimates are at $55 million, 1.5% of the nation's GDP. Tomas may be the most damaging storm to affect the island since Hurricane Janet of 1955. The havoc wreaked by Tomas in the Lesser Antilles makes is likely that the name Tomas will be retired from the list of active hurricane names in the Atlantic.


Figure 1. Torrential rains from Tomas triggered massive flooding on St. Lucia that destroyed several bridges and severely damaged roads. Image credit: St. Lucia Star.

Tomas gradually strengthening
Satellite loops of Tomas show a considerably more organized storm than yesterday, with a modest but increasing amount of heavy thunderstorm activity. However, low-level spiral bands are limited, and upper-level outflow is weak, and Tomas is not in danger of building an eyewall today. Curacao radar shows that the echoes from Tomas are disorganized, with no spiral banding apparent. Wind shear has declined to a moderate 10 -15 knots and the atmosphere in the Caribbean has moistened over the past day, allowing Tomas to re-organize. A hurricane hunter aircraft is on its way to Tomas this morning, and will have a better estimate of the storm's strength by early this afternoon.


Figure 2. Curacao radar at 10:07am EDT on Tuesday, November 2, 2010, showed a large area of rain associated with Tomas over the central Caribbean, but these echoes were poorly organized.

Track forecast for Tomas
The ridge of high pressure pushing Tomas to the west has weakened, allowing Tomas to slow down slightly to a forward speed of 10 mph this morning. This speed will decrease further to 5 mph tonight, as a trough of low pressure approaches the eastern U.S. and breaks down the ridge. By Wednesday, the trough to Tomas' north should be able to pull the storm to the northwest. Tomas' outer spiral bands will bring heavy rains to southwestern Haiti and eastern Jamaica beginning on Thursday night. The computer models have come into better agreement that Tomas will turn more to the north-northeast by Friday, with Haiti or Jamaica the most likely landfall locations. NHC is giving Port-au-Prince, Haiti, a 50% chance of receiving tropical storm force winds, and a 6% chance of hurricane force winds. These odds are 45% and 7%, respectively for Kingston, Jamaica, and 23% and 3% for Santo Domingo in the Dominican Republic.

Tomas may stall
The models are increasingly suggesting the once Tomas begins moving to the north-northeast, the trough pulling the storm that direction will lift out, stranding Tomas in a region of weak steering currents. Tomas may then wander and dump heavy rains for several days, Saturday through Monday. Given recent model trends, I believe this is likely, but the exact location where Tomas might be stranded is uncertain. The NOGAPS model gives a nightmare scenario for Haiti, with Tomas remaining stationary just off the coast from Port-Au-Prince as a hurricane for many days. The UKMET stalls Tomas over the Turk and Caicos Islands, while the GFS, GFDL, and ECMWF models predict Tomas will stall several hundred miles north of Hispaniola and drift eastwards. It's reasonable to go with the model consensus and predict Tomas will pass over western Haiti and stall far enough north of the nation so that heavy rains will not linger over Hispaniola for many days. The uncertainties in the track forecast are greater than usual, though.

Intensity forecast for Tomas
Wind shear as diagnosed by the SHIPS model has dropped to the moderate range, 10 - 15 knots, and is predicted to stay low to moderate, 5 - 15 knots, for the remainder of the week. The relaxation of shear should allow Tomas to continue to re-organize over the next few days. Aiding this process will be an increasingly moist atmosphere. Dry air has decreased significantly over the past 24 hours, as seen on water vapor satellite imagery, and the models predict a very moist atmosphere will surround Tomas for the remainder of the week. With SSTs at a record warm 29.5°C and a very high ocean heat content, there is a substantial danger that Tomas will undergo a period of rapid intensification once it rebuilds its inner core and establishes an eyewall. This is not likely to happen today, but could occur as early as Wednesday night. This may give Tomas sufficient time to intensify into a major hurricane before landfall in Haiti or Jamaica, as predicted by the GFDL model. The most reasonable intensity forecast at this point is to call for a landfall on Friday at Category 2 strength, but Tomas could easily be anywhere from Category 1 to Category 3 hurricane strength on Friday. NHC is giving Tomas a 19% chance of reaching Category 3+ strength; I believe these odds are higher, 40%. With the atmosphere expected to be very moist, it is likely that Tomas will dump very heavy rains of 4 - 8 inches over much of Haiti, even if Tomas strikes as a tropical storm. Rains of this magnitude are capable of causing heavy loss of life due to extreme floods running down Haiti's deforested mountain slopes. Portlight.org is preparing to send their mobile kitchen with enough food to feed 500 people per day, if Tomas continues on its current forecast path.


Figure 3. Plot of all Category 1 and stronger hurricanes to pass within 50 miles of Barbados since reliable record keeping began in 1851. Image credit: NOAA Coastal Services Center.

Barbados hurricane history
Tomas is the strongest hurricane to affect Barbados since Category 3 Hurricane Allen of 1980, which passed just north of the island. Allen did $4 million in damage, compared to Tomas' $55 million. The deadliest hurricane in Barbados history was the Category 5 Great Hurricane of 1780, which killed approximately 4500 people on the island, and leveled every building, including the stone governor's mansion. The Great Hurricane of 1780 was also the Atlantic's deadliest hurricane of all-time, with 22,000 fatalities, mostly in the Lesser Antilles Islands.

Next update
I'll have an update Wednesday morning.

Jeff Masters

Hurricane

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Tomas remains weak; St. Lucia hard-hit by the storm

By: JeffMasters, 2:04 PM GMT on November 01, 2010

Hurricane Tomas dealt a punishing blow to the Caribbean island of St. Lucia on Saturday, with the neighboring islands of St. Vincent and Barbados also suffering heavy damage. St. Lucia received the full brunt of the northern eyewall of Tomas as it intensified, and the St. Lucia weather service reported that sustained winds of 90 - 95 mph affected the island. A state of emergency has been declared, and heavy flooding washed out many bridges and roads. Damage to structures is considerable, with many roofs gone, and damage reported to hospitals, schools, and businesses. The Minister of Communications for the island said yesterday that he had done an aerial assessment of the damage, and it was "worse that we could think of." The Caribbean Catastrophe Risk Insurance Facility estimated that they will pay out $8.5 million for Barbados, $3.2 million for Saint Lucia, and $1.1 million for St Vincent and the Grenadines.


Figure 1. Torrential rains from Tomas triggered massive flooding on St. Lucia that destroyed several bridges and severely damaged roads. Image credit: Caribbean Hurricane Network.

Tomas remains weak
Satellite loops of Tomas show the classic signature of a tropical storm experiencing high wind shear, with a low-level swirl of clouds and the heavy thunderstorm activity all pushed to the east side of the circulation by strong upper-level winds out of the southwest. A few flare-ups of thunderstorms have occurred near the center of Tomas this morning, a sign that the storm is not going to die anytime soon. Wind shear is a high 20 knots due to strong upper level southwest winds, and these winds are driving dry air at mid-levels of the atmosphere into Tomas' west side, as seen on water vapor satellite imagery.


Figure 2. Morning satellite image of Tropical Storm Tomas.

Track forecast for Tomas
The ridge of high pressure pushing Tomas to the west-northwest will weaken by Tuesday, as a trough of low pressure approaches the eastern U.S. and breaks down the ridge. This will result in Tomas slowing from its current 14 mph forward speed to 5 mph by Tuesday afternoon. By Thursday, the trough to Tomas' north should be able to pull the storm to the north or north-northeast. The exact timing and location of this turn is still uncertain, but the computer models have come into better agreement that Haiti or Jamaica are the most likely targets of Tomas. NHC is giving Port-au-Prince, Haiti, a 40% chance of receiving tropical storm force winds, and a 5% chance of hurricane force winds. These odds are slightly lower for Kingston, Jamaica--29% and 4%, respectively.

However, the latest 2am EDT (06Z) run of the NOGAPS model calls into question whether or not the trough will be strong enough to pull Tomas northward into Haiti. The NOGAPS is keeping Tomas trapped in the Caribbean for the next seven days. The latest runs of the GFS and ECMWF models are also showing that the trough will not be strong enough to pull Tomas fully out to sea, and these models stall the storm just north of Haiti. So, the long-term fate of Tomas is now looking murkier, and the storm may still be in the Caribbean a week from now.

Intensity forecast for Tomas
Wind shear is forecast to remain in the high range today, near 20 knots, then decline to the moderate range, 10 - 20 knots, Tuesday through Wednesday. The relaxation of shear should allow Tomas to re-organize Tuesday and Wednesday, though it is unlikely the storm could rebuild its inner core and form and eyewall until Thursday at the earliest. Hampering this process will be the presence of a considerable amount of dry air to Tomas' west. The upper-level winds out of the southwest creating the shear over Tomas will drive this dry air into the core of the storm, slowing intensification. The waters are very warm in the Caribbean and these waters extend to great depth, so a period of rapid intensification just before landfall in Jamaica or Haiti is possible, particularly if the shear drops to the low range, as predicted by the latest SHIPS model forecast. The current south of due west motion of Tomas is putting the storm farther south in the Caribbean than originally expected, which will give the storm more time over water and more time to intensify. The intensity Tomas might have at landfall is thus highly uncertain, and a strength anywhere between a tropical storm and Category 3 hurricane would not be surprising. The HWRF model predicts Tomas will be a strong tropical storm with 70 mph winds on Friday at landfall, while the GFDL foresees Tomas will be a strengthening Category 3 hurricane as it bears down on Haiti Saturday morning. The HWRF model has been under-forecasting intensity this season, and I predict Tomas will be a strengthening Category 1 hurricane on Friday as it makes landfall in Jamaica or Haiti.


Figure 3. Plot of all Category 1 and stronger hurricanes to pass within 50 miles of St. Lucia since reliable record keeping began in 1851. Image credit: NOAA Coastal Services Center.

St. Lucia's hurricane history
Tomas is the strongest hurricane to affect St. Lucia since Category 1 Hurricane Dean of 2007 brought 90 mph winds to the island. Dean killed one person and did $6.4 million in damage--0.5% of the nation's GDP. The island's strongest hurricane since accurate records began in 1851 was Hurricane Allen of 1980, which struck as a Category 3 hurricane with 130 mph winds. Allen killed 18 people on St.Lucia, and caused catastrophic damage of $235 million dollars ($613 million 2010 dollars.) This was 177% of the nation's GDP that year. The deadliest hurricane in St. Lucia history was the Category 5 Great Hurricane of 1780, which killed approximately 700 people. The Great Hurricane of 1780 was the Atlantic's deadliest hurricane of all-time, with 22,000 fatalities, mostly in the Lesser Antilles Islands.

Next update
I'll have an update Tuesday morning.

Jeff Masters

Hurricane

Updated: 6:06 PM GMT on November 01, 2010

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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.

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