Dr. Jeff Masters' WunderBlog

Top ten global weather events of 2011

By: JeffMasters, 7:00 PM GMT on December 30, 2011

A remarkable blitz of extreme weather events during 2011 caused a total of 32 weather disasters costing at least $1 billion worldwide. Five nations experienced their most expensive weather-related natural disasters on record during 2011--Thailand, Australia, Colombia, Sri Lanka, and Cambodia. According to insurance broker AON Benfield's November Catastrophe Report, the U.S. was hit by no less than seventeen punishing multi-billion dollar extreme weather disasters in 2011; NOAA's National Climatic Data Center official total is lower--twelve--but is likely to grow in number as additional damage statistics are tallied. Brazil experienced its deadliest weather-related natural disaster--a flash flood that killed 902 people in January, and the Philippines had its second deadliest flood ever, when Tropical Storm Washi killed over 1200 people in December.





It was difficult to pick a top ten list of top weather events of 2011 from this bewildering list of candidates, and I cheated a bit by giving a tie for tenth place, so that eleven events would make the list. My list of top weather events were chosen based on their impact to society and meteorological significance. Damage estimates and death tolls for the 2011 disasters were mostly taken from AON Benfield's November Catastrophe Report, and records for damages and death tolls from disasters in previous years was taken from the Centre for Research on the Epidemiology of Disasters (CRED.) Here, then, is this year's top ten list. I've included links to some of my blogs posts made at the time of the disaster.

1) East Africa drought and famine: over 30,000 dead
The deadliest weather disaster of 2011 was a quiet one that got few headlines--the East African drought in Somalia, Kenya, and Ethiopia. On July 20, the United Nations officially declared famine in two regions of southern Somalia, the first time a famine has been declared by the UN in nearly thirty years. Almost 30,000 children under the age of five were believed to have died of malnutrition in Somalia this summer, and the total death toll of this great drought is doubtless much higher. East Africa has two rainy seasons--a main "long rains" of March - June, and the "short rains" of October - November. The "short rains" failed in the fall of 2010, and when the main "long rains" in spring 2011 also failed, it brought one of the worst droughts in recorded history. The 2010 - 2011 drought was rated along with the droughts of 1983 - 1984 and 1999 - 2000 as one of the three most significant droughts of the past 60 years. It was the driest 12-month period on record at some locations in East Africa. Damage assessments from the drought are not yet available, but it would not be a surprise if the drought of 2011 was the costliest weather-related natural disaster on record for Somalia, Ethiopia, and Kenya.

December 20 post: Deadliest weather disaster of 2011: the East African drought


Figure 1. Children fetch water at a tap installed by the International Rescue Committee (IRC) in the village of Darssalam in central Somalia. Image credit: IRC.

2) Thailand flooding: most expensive natural disaster in Thai history
Heavy monsoon and tropical cyclone rains from July through October, enhanced by La Niña conditions, led to unprecedented flooding that killed 657 people and caused Thailand's most expensive natural disaster in history. Damages are now estimated at $45 billion by re-insurance company AON Benfield. This is 18% of the country's GDP. Hurricane Katrina cost the U.S. about 0.7% of its GDP, so the Thailand floods can be thought of as a disaster 25 times worse than Katrina for that country. Thailand's previous most expensive natural disaster was the $1.3 billion price tag of the November 27, 1993 flood, according to the Centre for Research on the Epidemiology of Disasters (CRED). The floodwaters this year have hit 83% of Thailand's provinces, affected 9.8 million people, and damaged four million structures and approximately 25% of the nation's rice crop. Thailand is the world's largest exporter of rice, accounting for 30% of the global total, and the flood has helped trigger an increase in world rice prices in late 2011.

November 14 post: Thailand's flood gradually subsiding; climate change increasing Thai flood risk


Figure 2. An SH-60F Sea Hawk helicopter assigned to Helicopter Anti-Submarine Squadron (HS) 14, flies around the Bangkok area with members of the humanitarian assessment survey team and the Royal Thai Armed Forces to assess the damage caused by the 2011 floods. Image credit: Petty Officer 1st Class Jennifer Villalovos

3) Queensland, Australia flooding: most expensive natural disaster in Australian history
Heavy rains from December 2010 through January 2011, enhanced by La Niña conditions and record-warm ocean temperatures, led to unprecedented rains and flooding that killed 35 people and did $30 billion in damage. This was 3.2% of Australia's GDP, and five times more costly than the nation's previous most expensive natural disaster in history, the 1981 drought ($6 billion.) Rainfall in Queensland and all of eastern Australia in December 2010 was the greatest on record, and the year 2010 was the rainiest year on record for Queensland.

January 21 post: 2011: Year of the Flood


Figure 3. Still frame from a remarkable 6-minute YouTube video showing the sad fate of a row of parked cars when a flash flood in Toowoomba, Queensland sweeps away dozens of the cars. A note to the wise: Two minutes into the video, we see a man enter the flash flood to save his car. He is successful, but his actions were extremely risky--most flash flood deaths occur when cars with people inside get swept away.

4) Columbia floods: most expensive natural disaster in Colombia's history
Heavy rains in Colombia reached their peak in late April, triggering floods that killed 116 and did $5.85 billion in damage (2% of their GDP), making it the most damaging natural disaster in Colombia's history. Colombian President Juan Manuel Santos warned: “There are going to be a lot of needy people, there has never been a tragedy of this scale in our history.” Colombia's previous most expensive weather disaster occurred just last year, when the heaviest rains in 42 years of record keeping occurred. Floods and landslides killed 528, did $1 billion in damage, and left 2.2 million homeless in 2010. Colombia's most expensive natural disaster prior to 2011 was the $1.9 billion in damage from the January 25, 1999 earthquake, according to CRED.

5) Tropical Storm Washi: second deadliest weather disaster in Philippine history
Tropical Storm Washi hit the southern Philippine island of Mindanao as a tropical storm with 45 - 55 mph winds, crossing the island in about eighteen hours on December 16. Washi was unusually wet, as the storm was able to tap a large stream of tropical moisture extending far to the east, and drew moisture from an area where sea surface temperatures were nearly 1°C above average--one of the top five warmest values on record. Washi's rains fell on regions where the natural forest had been illegally logged or converted to pineapple plantations, and the heavy rains were able to run off quickly on the relatively barren soils and create devastating flash floods. Since the storm hit in the middle of the night, and affected an unprepared population that had no flood warning system in place, the death toll was tragically high. At least 1249 people perished, and 79 people are still listed as missing. The only deadlier storm ever to hit the Philippines was Tropical Storm Thelma on November 5, 1991, which killed 5956 people.

December 19 post: Tropical Storm Washi kills 632 in the Philippines


Figure 5. MODIS true-color satellite image of Tropical Storm Washi at 01:45 UTC December 16, 2011, as it bore down on the Philippines. At the time, Washi had top sustatined winds of 50 mph. Image credit: NASA.

6) Brazil flash flood kills 902: deadliest natural disaster in Brazil's history
Brazil suffered its deadliest natural disaster in history on January 11, when torrential rains inundated a heavily populated, steep-sloped area about 40 miles north of Rio de Janeiro. Flash floods and mudslides from the heavy rains have claimed 902 lives, including at least 357 in Nova Friburgo and 323 in Teresópolis. Rainfall amounts of approximately 300 mm (12 inches) fell in just a few hours in the hardest-hit regions. Damage estimates are $1.2 billion, making it the most damaging storm in Brazil's history, and third most damaging natural disaster, behind the $2.3 billion and $1.7 billion price tags of the 1978 and 2004 droughts. The previous deadliest flood in Brazilian history was a January 23, 1967 flood that killed 785 people.

January 14 post: At least 611 dead in Brazilian floods: Brazil's deadliest natural disaster in history


Figure 6. Flooded stream in Teresópolis. Image credit: Wikipedia.

7) April 25 - 28 Super" tornado outbreak kills 321 in the U.S.
On April 25 - 28, 2011, a massive tornado outbreak clobbered the Midwest and Southeast U.S. with 343 tornadoes. Now called the April 2011 Super tornado outbreak, it was the largest and most damaging tornado outbreak in U.S. history. The tornadoes caused 321 deaths, with 240 of those occurring in Alabama. The deadliest tornado of the outbreak, an EF-5, hit northern Alabama, killing 78 people. Several major metropolitan areas were directly impacted by strong tornadoes including Tuscaloosa, Birmingham, and Huntsville in Alabama and Chattanooga, Tennessee, causing the estimated damage costs to soar. The outbreak caused more than $7.3 billion insured losses and total losses greater than $10.2 billion.

April 29 post: Over 300 dead in historic tornado outbreak; one violent EF-5 tornado confirmed


Figure 7. The Piggly Wiggly supermarket and Family Dollar store after the EF-5 Hackleburg, Alabama tornado on April 27. Image credit: NWS Birmingham, Alabama.

8) Southern U.S./Northern Mexico drought: $10 billion in damage, and rising
Drought and excessive heat created major impacts across Texas, Oklahoma, New Mexico, Arizona, southern Kansas, western Louisiana, and northern Mexico. Texas endured its driest 1-year period on record, and rainfall in much of northern Mexico was the lowest since record keeping began in 1941. Texas had the hottest summer ever recorded by a U.S. state, and Oklahoma had the hottest month (July) any U.S. state has ever recorded. The total direct losses to crops, livestock and timber are estimated at $10 billion, but are expected to continue to rise as the drought continues into 2012. Record fires across the region caused an additional $1 billion in damage.

August 17 post: Texas heat wave smashes more records


Figure 8. Business was slow at the Lake Conroe, Texas jet ski rental in 2011, thanks to the great Texas drought of 2011. Image credit: wunderphotographer BEENE.

9) Pakistan floods: 2nd most expensive weather disaster in Pakistani history
Heavy rains during the July through September monsoon season triggered devastating flooding that killed 456 and did $2 billion in damage (1.1% of GDP) in Pakistan. It was the second most expensive weather-related disaster in Pakistan's history, behind the $9.5 billion price tag of the 2010 floods (5.5% of GDP.)

10 (tie) Hurricane Irene: most damaging tropical cyclone of 2011
The most damaging tropical cyclone on the globe during 2011 was Hurricane Irene, which plowed through the Bahama Islands as a Category 3 hurricane with 120 mph winds before striking North Carolina as a Category 1 hurricane with 85 mph winds on August 27. Most of Irene's damage occurred after it made landfall on Long Island, New York as a tropical storm with 65 mph winds, when torrential rainfall triggered extreme flooding in the Northeast U.S. More than 7 million homes and businesses lost power during the storm. Irene caused at least 45 deaths in the U.S., and ten in the Caribbean and Bahamas. Damage is estimated at $7.3 billion.

December 3 post: Hurricane Irene: New York City dodges a potential storm surge mega-disaster


Figure 9. GOES-East visible satellite image of Irene taken at 7:45 am EDT on Sunday, August 28, 2011. At the time, Irene was a tropical storm with 65 mph winds, making landfall on Long Island, New York. Image credit: NOAA Environmental Visualization laboratory.

10 (tie) May 22 - 27 Joplin, Missouri tornado outbreak
A violent EF-5 tornado carved a ½ – ¾ mile-wide path of devastation through Joplin, Missouri on May 22, killing 158, and causing $3 billion in damage. Huge sections of the town virtually obliterated, and damage from the tornado was so severe that pavement was ripped from the ground. It was the largest death toll from a U.S. tornado since 1947, seventh deadliest tornado in U.S. history, and the most expensive tornado in world history. The six-day outbreak spawned 180 tornadoes in the central and southern states, killed 177, and did $9.1 billion in damage.

May 23 post: Deadliest U.S. tornado since 1953 rips through Joplin, Missouri, killing 89


Video 1. Video of the Joplin, Missouri tornado of May 22, 2011, entering the southwest side of town. Filmed by TornadoVideos.net Basehunters team Colt Forney, Isaac Pato, Kevin Rolfs, and Scott Peake. The most remarkable audio I've ever heard of people surviving a direct hit by a violent tornado was posted to Youtube by someone who took shelter in the walk-in storage refrigerator at a gas station during the Joplin tornado. There isn't much video.

Honorable mentions:
1) Sri Lanka: Heaviest rains in nearly a century of record keeping triggered a 1-in-100 year flood in January that killed 43 and did $500 million in damage--the costliest weather-related disaster in Sri Lanka's history. Renewed rains February 1 - 10 caused flooding that killed 18 and cost an additional $450 million--the second most costly natural disaster in Sri Lanka's history.

2) Heavy rains in September and October in Cambodia triggered flooding that killed 250 and did $521 million in damage--by far the most expensive natural disaster in Cambodian history. The previous most expensive disaster was the $160 million cost of floods in July 2000.

3) El Salvador: Heavy rains from Tropical Depression 12-E in October triggered flooding that killed 140 in Central America and caused $900 million in damage to El Salvador (4.2% of GDP). This is the 2nd most expensive weather-related disaster in El Salvador's history, behind the $939 million price tag of their Nov. 7, 2009 flood.

4) China: June floods in China killed 239, doing $6.65 billion in damage, the 10th most damaging weather-related disaster in Chinese history.

5) China: September floods killed 101 and did $4.25 billion in damage.

6) U.S.: Greatest flood on the Lower Mississippi River on record caused $4 billion in damage.

7) China: A drought in Northern China during January through April cost $2.7 billion.

8) Denmark: Severe flooding on July 2 - 3 caused $1 billion in damage, the 3rd most expensive weather-related disaster in Danish history.

Other posts looking back at the remarkable weather events of 2011
2011: Year of the Tornado
Deadliest weather disaster of 2011:; the East African drought
Tropical Storm Lee's flood in Binghamton: was global warming the final straw?
Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.
Hurricane Irene: New York City dodges a potential storm surge mega-disaster

Donations sought for the East Africa famine
Weather Underground has partnered with the International Rescue Committee (IRC) to help the Horn of Africa region during the ongoing famine. With the help of the Weather Underground community, we hope to raise $10,000 that will go toward helping the refugees survive the crisis. Weather Underground will match the community's donation dollar-for-dollar up to $10,000 for a total donation of $20,000. Please visit the East Africa famine donation page to help out. Ninety cents of every dollar donated goes directly to the people in need.

This will be my last post until Tuesday, as its time to gather with family and friends and celebrate the arrival of the new year. Happy New Year, everyone!

Jeff Masters

Extreme Weather Climate Summaries

Updated: 6:56 PM GMT on December 31, 2011

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2011: Year of the Tornado

By: JeffMasters, 7:25 PM GMT on December 27, 2011

The year 2011 will forever be known as Year of the Tornado in the U.S. A series of violent severe storms swept across the Plains and Southeast U.S., bringing an astonishing six billion-dollar disasters in a three-month period. The epic tornado onslaught killed 552 people and caused $25 billion in damage. Three of the five largest tornado outbreaks on record hit in a six-week period, including the largest and most expensive tornado outbreak in U.S. history--the $10.2 billion dollar Southeast U.S. Super Outbreak, April 25 - 28. Even more stunning was the $9 billion late-May tornado outbreak that brought an EF-5 tornado to Joplin, Missouri. The Joplin tornado did $3 billion in damage and killed 158 people--the largest death toll from a U.S. tornado since 1947, seventh deadliest tornado in U.S. history, and the most expensive tornado in world history. In a year of amazing weather extremes, this year's tornado season ranks as the top U.S. weather story of 2011.


Video 1. Remarkable video of the tornado that hit Tuscaloosa, Alabama on April 27, 2011. Fast forward to minute four to see the worst of the storm.



Figure 1. A truly frightening radar image: multiple hook echoes from at least ten supercell thunderstorms cover Mississippi, Alabama, and Tennessee during the height of the April 27, 2011 Super Outbreak. A multi-hour animation is available here.

A record six EF-5 tornadoes confirmed in 2011
Six top-end EF-5 tornadoes hit the U.S. in 2011, tying this year with 1974 for the greatest number of these most destructive tornadoes. The EF-5 tornadoes of 2011:

1) The April 27, 2011 Neshoba/Kemper/Winston/Noxubee Counties, Mississippi tornado (3 killed, 29 mile path length.)

2) The April 27, 2011 Smithville, Mississippi tornado (22 killed, 15 mile path length.)

3) The April 27, 2011 Hackleburg, Alabama tornado (71 killed, 25 mile path length.)

4) The April 27, 2011 Rainsville/Dekalb County, Alabama tornado (26 killed, 34 mile path length.)

5) The May 22, 2011 Joplin Missouri tornado (158 killed, 14 mile path length.)

6) The May 24, 2011 Binger-El Reno-Peidmont-Guthrie, Oklahoma tornado. (9 killed, 75 mile path length.)


Figure 2. Aerial view of damage from the May 22, 2011 Joplin, Missouri tornado. Image credit: Wikipedia.


Figure 3. EF-5 damage from the April 27, 2011 Neshoba tornado in Mississippi. The tornado was so powerful that it dug out the ground to a depth of two feet over an area 25 - 50 yards wide and several hundred yards long. Image credit: NWS.

A few other remarkable statistics on the tornado season of 2011, compiled from NOAA's official press release, the NOAA Extreme Weather 2011 page, and Wikipedia's excellent tornado pages:

- The tornado death toll of 552 in 2011 ties 1936 as the second deadliest year for tornadoes in U.S. history. Only 1925, with 794 fatalities, was deadlier. In 1936, violent tornadoes hit Tupelo Mississippi (216 killed), and Gainesville, Georgia (203 killed.) During the 1930s, the tornado death rate per million people was 60 - 70 times as great as in the year 2000 (Figure 4), implying that this year's tornadoes may have killed tens of thousands of people if we did not have our modern tornado modern warning system.


Figure 4. Death rate per million people per year in U.S., 1875-2011. Thin line with dots is raw rate, curved thick line is death rate, filtered by 3-point median and 5-point running mean filter, and straight solid lines are least squares fit to filtered death rate for 1875-1925 and 1925-2011. Dashed lines are estimates of 10th and 90th percentile death rates from 1925-2000. The death rate fell from 8 per million to .12 per million between 1940 and 2010. Image credit: A Brief History of Deaths from Tornadoes in the United States, Harold Brooks and Charles Doswell III, and updated by Harold Brooks in 2011.

- April 2011 had the most tornadoes of any month in U.S. history--753. The previous record was 542, set in May 2003. The previous busiest April was in 1974, with 267 tornadoes. The average number of tornadoes for the month of April during the past decade was 161, and the 30-year average for April tornadoes was 135.

- On April 27, 199 confirmed tornadoes touched down. This is the largest 1-day tornado total on record, beating the 148 recorded in 24 hours on April 3 - 4, 1974.

The year 2011 now has three of the top five tornado outbreaks on record (note, though, that reliable records for number of tornadoes only extend back in time to about the early 1990s):

- The April 25 - 28, 2011 Super tornado outbreak, with 343 tornadoes, is now the largest tornado outbreak in U.S. history. The previous record (3 days or less duration) was 148 tornadoes, set during the April 3 - 4, 1974 Super Outbreak.

- The May 22 - 27, 2011 tornado outbreak, with 180 confirmed tornadoes, ranks as the 4th largest 6-day or shorter tornado outbreak on record. A May 2003 6-day outbreak had 289 tornadoes, and a May 2004 6-day outbreak had 229 tornadoes.

- The April 14 - 16, 2011 tornado outbreak, with 177 confirmed tornadoes, ranks as the second largest tornado outbreak of three days or less duration on record, and 5th largest outbreak of six or fewer days duration.

- The May 22, 2011 Joplin, Missouri tornado killed 158 people and injured 1150, making it the deadliest U.S. tornado since 1947, and 7th deadliest in history. The $3 billion estimate of insured damage makes it the most expensive tornado in world history.

- Preliminary damage estimates from Munich Re insurance company put 2011's insured losses due to U.S. thunderstorms and tornadoes at $25 billion, more than double the previous record set in 2010.

- The year 2011 now ranks in 2nd place behind 1973 for greatest number of tornadoes greater than EF-0 strength (EF-1, EF-2, EF-3, EF-4 and EF-5 strength, Figure 5.)


Figure 5. Number of EF-1, EF-2, EF-3, EF-4 and EF-5 tornadoes from 1950 to 2011. The total shown for 2011 is preliminary and uses unofficial numbers through November 17, but 2011 now ranks in 2nd place behind 1973. There is not a decades-long increasing trend in the numbers of tornadoes stronger than EF-0, implying that climate change, as yet, is not having a noticeable impact on U.S. tornadoes. However, statistics of tornado frequency and intensity are highly uncertain. Major changes in the rating process occurred in the mid-1970s (when all tornadoes occurring prior to about 1975 were retrospectively rated), and again in 2001, when scientists began rating tornadoes lower because of engineering concerns and unintended consequences of National Weather Service policy changes. Also, beginning in 2007, NOAA switched from the F-scale to the EF-scale for rating tornado damage, causing additional problems with attempting to assess if tornadoes are changing over time. Data provided by Harold Brooks, NOAA/National Severe Storms Laboratory.

Other posts looking back at the remarkable weather events of 2011
Deadliest weather disaster of 2011: the East African drought
Tropical Storm Lee's flood in Binghamton: was global warming the final straw?
Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.
Hurricane Irene: New York City dodges a potential storm surge mega-disaster

The NWS posted a summary of the records set during the tornado season of 2011 in February 2012.

Jeff Masters

Tornado Extreme Weather

Updated: 8:45 PM GMT on March 05, 2012

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A white Christmas will be a U.S. rarity in 2011; November the globe's 12th warmest

By: JeffMasters, 7:26 PM GMT on December 22, 2011

A white Christmas will be a rarity across most of the U.S. this year, as December temperatures have been more typical of November, and very little snow has fallen. Large portions of the eastern half of the country have been more than 4°F above average so far in December, with temperatures averaging 8°F above average over portions of North Dakota.This is quite a switch from the previous two winters, which were both much colder and snowier than average. All three winters featured La Niña conditions in the Eastern Pacific Ocean, so that cannot explain the difference. A key reason for the December warmth this year and the cold and snowy Decembers of 2010 and 2009 is a weather pattern known as the Arctic Oscillation.


Figure 1. Departure of temperature from average over the 30-day period ending on December 22, 2011. Image credit: NOAA/CPC.



Figure 2. Top: snow depth measured in the U.S. on December 22, 2011, after a month with a strong positive phase of the Arctic Oscillation (AO). Bottom: Snow depth measured in the U.S. on December 22, 2010, after a month with a strong negative phase of the Arctic Oscillation (AO). Image credit: NOAA/NOHRSC.

The Arctic Oscillation and its influence on winter weather
The Arctic Oscillation (AO), and its close cousin, the North Atlantic Oscillation (NAO), are climate patterns in the Northern Hemisphere defined by 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 AO and NAO control 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 AO/NAO) leads to increased westerly winds and mild winter in the U.S. and Western Europe. Positive AO/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 AO/NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. Negative AO/NAO winters tend to bring cold winters to Europe and the U.S. East Coast, but leads to very warm conditions in the Arctic, since all the cold air spilling out of the Arctic gets replaced by warm air flowing poleward. The winter of 2009 - 2010 had the most extreme negative NAO and AO since record keeping began in 1865; a very extreme AO/NAO also developed during the winter of 2010 - 2011. But this year, the pattern has flipped. The AO has been almost as strong, but in the opposite sense--a positive AO, leading to very warm conditions over the U.S. Unfortunately, the AO is difficult to predict more than a week or two and advance, and we don't understand why the AO can vary so much from winter to winter. The latest predictions from the ECMWF and GFS models show this positive AO pattern continuing for at least the next ten days. Real winter conditions won't arrive in the U.S. until the first week of January, at the earliest. Between now and the end of 2011, the only major winter storm the GFS model expects in the U.S. will be in the Pacific Northwest, on December 30 - 31.

This week, NOAA's ClimateWatch Magazine posted an excellent tutorial on the Arctic Oscillation and how it is affecting our winter weather this year.



Figure 3. The departure of temperature from average in Centigrade during the November - December - January period during various phases of the Arctic Oscillation (AO). Positive AO conditions lead to warm winters in the U.S., while negative AO conditions lead to cold winters. Image credit: NOAA/CPC.

November 2011: Earth's 12th warmest on record
November 2011 was the globe's 12th warmest November on record, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC). November 2011 global land temperatures were the 16th warmest on record, and ocean temperatures were the 12th warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere near average, the 20th or 11th warmest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the November 2011 Global Weather Extremes Summary.


Figure 4. Departure of temperature from average for November 2011. Image credit: National Climatic Data Center (NCDC).

A warm November for the U.S.
In the contiguous U.S., November ranked as the 25th warmest November in the 117-year record. Thirteen states in the Northeast and Upper Midwest recorded a top-ten warmest November, and no states had a top-ten coldest November. Eight states had a top-ten wettest November--Indiana, Ohio, Missouri,Illinois, Kentucky, Tennessee, Arkansas, and Oklahoma. One state had a top-ten driest month, Minnesota. Texas had its 39th driest November on record, keeping 76% of Texas under extreme to exceptional drought as of December 13, according to the U.S. Drought Monitor.

A weak La Niña continues
A borderline weak/moderate La Niña event continues in the equatorial Pacific, where sea surface temperatures were approximately 1.0°C below average during the first half of December. The impacts of a La Niña on U.S. weather are well-defined. It is likely that the drought in the South, especially Texas, will continue, along with above average temperatures. The Northwest can expect cooler than average temperatures, as well as the potential for another winter with a heavy snowpack across the western United States.

Arctic sea ice extent third lowest on record
Arctic sea ice extent was at its third lowest on record in November, behind 2006 and 2010, according to the National Snow and Ice Data Center. Sea ice records date back to 1979.

Donations sought for the East Africa famine
Weather Underground has partnered with the International Rescue Committee (IRC) to help the Horn of Africa region during the ongoing famine. With the help of the Weather Underground community, we hope to raise $10,000 that will go toward helping the refugees survive the crisis. Weather Underground will match the community's donation dollar-for-dollar up to $10,000 for a total donation of $20,000. Please visit the East Africa famine donation page to help out. Ninety cents of every dollar donated goes directly to the people in need.

Posts looking back at the remarkable weather events of 2011
Deadliest weather disaster of 2011: the East African drought
Tropical Storm Lee's flood in Binghamton: was global warming the final straw?
Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.
Hurricane Irene: New York City dodges a potential storm surge mega-disaster

This will be my last post until Tuesday. Have a great holiday, everyone!

Jeff Masters

Winter Weather Climate Summaries

Updated: 2:34 AM GMT on December 24, 2011

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Deadliest weather disaster of 2011: the East African drought

By: JeffMasters, 5:07 PM GMT on December 20, 2011

The deadliest storm of 2011 is Tropical Storm Washi, which is now being blamed for 957 deaths in the Philippines. Washi's heavy rains triggered devastating flash flooding on the island of Mindanao last Friday. However, the deadliest weather disaster of 2011 is a quiet one that has gotten few headlines--the East African drought in Somalia, Kenya, and Ethiopia. On July 20, the United Nations officially declared famine in two regions of southern Somalia, the first time a famine has been declared by the UN in nearly thirty years. Almost 30,000 children under the age of five were believed to have died of malnutrition in Somalia this summer, and the total death toll of this great drought is doubtless much higher. At least thirteen million people in East Africa are in need of food aid. However, conditions are improving. Food aid has lifted three of six provinces in Somalia out of famine. The "short rains" of the October - November rainy season were plentiful this year--too much so, since heavy rains killed 15 people in Kenya and left 80,000 homeless in early December. The flooding was worsened by the preceding drought, which killed much of the vegetation that ordinarily would have stabilized the soil and absorbed rainwater before it could run off and create destructive floods. The rains have allowed a good harvest to be planted this fall, and with continued food aid, the Somalia famine should ease by spring 2012. ReliefWeb reports that in the three Somalian provinces still experiencing famine, nearly 250,000 people face imminent starvation, though.


Figure 1. The impacts of the Horn of Africa drought on cattle in Somalia in 2006. Image credit: USGS

Meteorology of the East Africa drought
East Africa has two rainy seasons--a main "long rains" of March - June, and the "short rains" of October - November. The "short rains" failed in 2010, due to a sea surface temperature pattern featuring cooler than average waters in the western Indian Ocean, and warmer than average waters in the Eastern Indian Ocean (a negative "Indian Ocean Dipole.") When the main "long rains" in spring 2011 also failed, it brought one of the worst droughts in recorded history. The 2010 - 2011 drought was rated along with the droughts of 1983 - 1984 and 1999 - 2000 as one of the three most significant droughts of the past 60 years. It was the driest 12-month period on record at some locations in East Africa.


Figure 2. The "long rains" of March - May 2011 failed over much of East Africa, leading to drought and famine (left image.) However, the "short rains" of October - December have been up to five times higher than normal, easing the East Africa drought. Image credit: NOAA Climate Prediction Center.

The uncertain future of drought in East Africa
The climate of East Africa during the main March - June rainy season has steadily dried over the past 30 years. Since 2004, six of the past eight years have seen unusually deficient spring "long rains." This drying of the East African climate has come as the waters of the Indian Ocean have warmed significantly. A 2011 study by A. Park Williams and Chris Funk of the University of California, Santa Barbara, blames the drought in East Africa on the heating up of the Indian Ocean, which has altered the atmospheric circulation over East Africa to bring more sinking air and less moisture. The atmospheric circulation over East Africa is part of Earth's largest atmospheric circulation feature--the Walker circulation. The Walker circulation features rising air over the warmest waters of the Pacific Ocean, and compensating sinking air over over eastern tropical Africa and the eastern tropical Pacific. The Walker circulation also helps drive the El Niño/La Niña phenomena in the Eastern Pacific. Williams and Funk show that the increase in Indian Ocean temperatures in recent decades has made the Walker circulation extend farther west, resulting in more sinking air over East Africa and thus less rain. Since the increase in Indian Ocean temperature driving this change in the atmospheric circulation shows strong linkages with human-caused global warming, they conclude: "anthropogenic [human-caused] warming appears to have already significantly altered the Earth's largest circulation feature and impacted its most food insecure inhabitants." They predict that East Africa will continue to dry as global warming increases the ocean temperatures in the Indian Ocean, impacting the Walker circulation. However, eighteen of the 21 models used in the 2007 IPCC report on climate change predict more rainfall over East Africa by the end of this century. These models predict that the Walker circulation will weaken, shifting towards a more "El Niño-like" state, resulting in less sinking air (and thus more rain) over East Africa. Since there is as yet no evidence of this happening, and East African climate has gotten drier in recent years, this may be a case where the large majority of the climate models are wrong. While the models used to formulate the 2007 IPCC report do a reasonable job simulating the the current climate over most of the world, they do a poor job of simulating Africa's current climate. The models put too much precipitation in southern Africa, and displace the band of heavy thunderstorms called the Intertropical Convergence Zone (ITCZ) too far south. The 2007 IPCC report concludes, "the absence of realistic variability in the Sahel in most 20th-century simulations casts some doubt on the reliability of models". In other words, since these models do a poor job simulating the current climate of the Sahel region of Africa, we shouldn't trust their predictions for the future climate of Africa.


Figure 3. Farmers in the Horn of Africa tend their emerging crops. Image credit: USGS.

Donations sought for the East Africa famine
Weather Underground has partnered with the International Rescue Committee (IRC) to help the Horn of Africa region during the ongoing famine. With the help of the Weather Underground community, we hope to raise $10,000 that will go toward helping the refugees survive the crisis. Weather Underground will match the community's donation dollar-for-dollar up to $10,000 for a total donation of $20,000. Please visit the East Africa famine donation page to help out. Ninety cents of every dollar donated goes directly to the people in need.

References
Behera, Swadhin K., Jing-Jia Luo, Sebastien Masson, Pascale Delecluse, Silvio Gualdi, Antonio Navarra, Toshio Yamagata, 2005: Paramount Impact of the Indian Ocean Dipole on the East African Short Rains: A CGCM Study. J. Climate, 18, 4514-4530. doi: http://dx.doi.org/10.1175/JCLI3541.1

Dai A., K.E. Trenberth, and T. Qian, 2004: A global data set of Palmer Drought Severity Index for 1870-2002: Relationship with soil moisture and effects of surface warming", J. Hydrometeorol., 5, 11171130.

Sheffield, J., K. M. Andreadis, E. F. Wood, and D. P. Lettenmaier, 2009, "Global and continental drought in the second half of the 20th century: severity-area-duration analysis and temporal variability of large-scale events", J. Climate 22, pp 1962-1981.

Williams, A.P., and C. Funk, 2011, A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa, Clim Dyn (2011) 37:2417-2435 DOI 10.1007/s00382-010-0984-y

Other posts looking back at the remarkable weather events of 2011
Tropical Storm Lee's flood in Binghamton: was global warming the final straw?
Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.
Hurricane Irene: New York City dodges a potential storm surge mega-disaster

Wunderground releases its free iPhone and Android apps
Wunderground is proud to announce that our free Weather Underground iPhone app is now live in the iTunes store. The free Android version was released on Android Market last night. I've been having a lot of fun with the new apps; they're a great way to get weather info on the go.

I'll have a new post on Thursday.

Jeff Masters

Drought Climate Change East Africa Drought Relief

Updated: 6:40 PM GMT on December 20, 2011

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Tropical Storm Washi kills 632 in the Philippines

By: JeffMasters, 3:47 PM GMT on December 19, 2011

The death toll on the Philippine island of Mindanao is at least 632, with hundreds still missing, in the wake of extreme flash flooding from Friday's passage of Tropical Storm Washi. (December 29 update: the death toll has risen to 1249, with 79 still missing.) Washi hit Mindanao as a tropical storm with 45 - 55 mph winds, crossing the island in about eighteen hours. Washi was unusually wet, as the storm was able to tap a large stream of tropical moisture extending far to the east (see the University of Wisconsin CIMSS satellite blog for imagery.) Aiding the heavy rains were sea surface temperatures that were nearly 1°C above average off the east coast of Mindanao, one of the top five warmest values on record. The exceptionally warm waters added about 7% more moisture than is usual for this time of year to the atmosphere. Washi hit a portion of the Philippines that does not see tropical storms and typhoons very often. Mindanao lies between 6°N and 9°N latitude, which is too close to the Equator for the Earth's spin to provide much help for a tropical storm trying to get spinning. Mindanao is thus hit only about once every twelve years by a significant tropical storm or typhoon. Washi's rains were not all that unusual for a Philippine tropical storm, with a peak rainfall amount of 7.44" (189 mm) observed in the city of Hinatuan. However, since the rains fell on regions where the natural forest had been illegally logged or converted to pineapple plantations, the heavy rains were able to run off quickly on the relatively barren soils and create devastating flash floods. Since the storm hit in the middle of the night, and affected an unprepared population that had no flood warning system in place, the death toll was tragically high. Washi is currently a tropical depression near the southern coast of Vietnam, and is dissipating.


Figure 1. MODIS true-color satellite image of Tropical Storm Washi at 01:45 UTC December 16, 2011, as it bore down on the Philippines. At the time, Washi had top sustatined winds of 50 mph. Image credit: NASA.


Figure 2. Track of Tropical Storm Washi. The storm crossed the Philippines unusually far to the south, near 8°N latitude.

Washi the deadliest tropical cyclone of 2011
The death toll from Washi is by far the highest for any tropical cyclone in 2011, surpassing the 215 people that died in Myanmar from Tropical Storm 02B in October. The deadliest storm in the world so far in 2011 occurred on January 11, when torrential rains of approximately 300 mm (12 inches) inundated a heavily populated, steep-sloped area about 40 miles north of Rio de Janeiro. Flash floods and mudslides from the heavy rains claimed 902 lives and caused $1.2 billion in damage. It was Brazil's deadliest storm in history. If we add Washi's toll to a list of deadliest storms of 2011 compiled by insurance broker AON Benfield, the Philippine disaster currently ranks as the third deadliest storm of 2011:



Deadliest natural disaster of 2011: the East Africa drought
While Tropical Storm Washi and the January 11 flash floods in Brazil are the deadliest storms of 2011, there is one weather-related disaster in 2011 that far surpasses these floods for number of people killed: the devastating East Africa drought in Somalia, Ethiopia, and Kenya. On July 20, the United Nations officially declared famine in two regions of southern Somalia--the first time a famine has been declared by the UN in nearly thirty years. Almost 30,000 children under the age of five were believed to have died of malnutrition in Somalia this summer, and the total death toll of this great drought is doubtless much higher. At least thirteen million people in East Africa are in need of food aid. Weather Underground has partnered with the International Rescue Committee (IRC) to help the Horn of Africa region during the ongoing famine. With the help of the Weather Underground community, we hope to raise $10,000 that will go toward helping the refugees survive the crisis. Weather Underground will match the community's donation dollar-for-dollar up to $10,000 for a total donation of $20,000. Please visit the International Rescue Committee donation page to help out. Ninety cents of every dollar donated goes directly to the people in need.

Winter storm Joachim batters Europe
One of the most intense storms in recent years carved a path across Western Europe December 15 - 17th. Named winter-storm ‘Joachim’, the center of the storm passed between France and the United Kingdom, then across the Low Countries and into Northwestern Germany and on to Poland. A peak wind gust of 211 kph (131 mph) was measured at Puy de Dome in Auvergne, France. In Germany, sustained winds of 87 mph were measured at Wendelstein at 8 pm local time on December 16th. The central pressure of Joachim fell as low as 963.8 mb (28.46”) in Braunschweig in western Germany, which may be the lowest pressure ever recorded in Germany. Wunderground's weather historian, Christopher C. Burt, has the details in his latest post.

Wunderground releases its free iPhone app
We are proud to announce that our free Weather Underground iPhone app is now live in the iTunes store. Don't worry Android users, we anticipate that the Android version will be live later today.

I'll have a new post on Tuesday.

Jeff Masters

Extreme Weather Hurricane

Updated: 6:04 PM GMT on December 29, 2011

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Our extreme weather: Arctic changes to blame?

By: JeffMasters, 9:50 PM GMT on December 16, 2011

"The question is not whether sea ice loss is affecting the large-scale atmospheric circulation...it's how can it not?" That was the take-home message from Dr. Jennifer Francis of Rutgers University, in her talk "Does Arctic Amplification Fuel Extreme Weather in Mid-Latitudes?", presented at last week's American Geophysical Union meeting in San Francisco. Dr. Francis presented new research in review for publication, which shows that Arctic sea ice loss may significantly affect the upper-level atmospheric circulation, slowing its winds and increasing its tendency to make contorted high-amplitude loops. High-amplitude loops in the upper level wind pattern (and associated jet stream) increases the probability of persistent weather patterns in the Northern Hemisphere, potentially leading to extreme weather due to longer-duration cold spells, snow events, heat waves, flooding events, and drought conditions.


Figure 1. Arctic sea ice in September 2007 reached its lowest extent on record, approximately 40% lower than when satellite records began in 1979. Sea ice loss in 2011 was virtually tied with the ice loss in 2007, despite weather conditions that were not as unusual in the Arctic. Image credit: University of Illinois Cryosphere Today.

Summertime Arctic sea ice loss: 40% since 1980
The Arctic has seen a stunning amount of sea ice loss in recent years, due to melting and unfavorable winds that have pushed large amounts of ice out of the region. Forty percent of the sea ice was missing in September 2007, compared to September of 1980. This is an area equivalent to about 44% of the contiguous U.S., or 71% of the non-Russian portion of Europe. Such a large area of open water is bound to cause significant impacts on weather patterns, due to the huge amount of heat and moisture that escapes from the exposed ocean into the atmosphere over a multi-month period following the summer melt.


Figure 2. The extent of Arctic sea ice loss in the summer July - August - September period in 2007 was about 1.4 million square miles (3.6 million square kilometers) greater than in 1980, according to the University of Illinois Cryosphere Today. For comparison, the lost ice coverage (orange colors) was equal to an area about 44% of the size of the contiguous U.S., or 71% of the non-Russian portion of Europe.

Arctic sea ice loss can slow down jet stream winds
Dr. Francis looked at surface and upper level data from 1948 - 2010, and discovered that the extra heat in the Arctic in fall and winter over the past decade had caused the Arctic atmosphere between the surface and 500 mb (about 18,000 feet or 5,600 meters) to expand. As a result, the difference in temperature between the Arctic (60 - 80°N) and the mid-latitudes (30 - 50°N) fell significantly. It is this difference in temperature that drives the powerful jet stream winds that control much of our weather. The speed of fall and winter west-to-east upper-level winds at 500 mb circling the North Pole decreased by 20% over the past decade, compared to the period 1948 - 2000, in response to the extra warmth in the Arctic. This slow-down of the upper-level winds circling the pole has been linked to a Hot Arctic-Cold Continents pattern that brought cold, snowy winters to the Eastern U.S. and Western Europe during 2009 - 2010 and 2010 - 2011.


Figure 3. West-to-east jet stream wind speeds at 500 mb (approximately 18,000 feet or 5,600 meters) in the mid-latitudes (40 - 60°N) over North America between 1948 and 2010. During fall (October - November - December) and winter (January - February - March), jet stream winds weakened by about 20%, from 13 - 14 m/s to 10.5 - 11 m/s. Spring (AMJ) and summer (JAS) winds changed little during this time period.

Arctic sea ice loss may increase the amplitude of jet stream troughs and ridges
The jet stream generally blows from west to east over the northern mid-latitudes, with an average position over the central U.S. in winter and southern Canada in summer. The jet stream marks the boundary between cold polar air to the north and warm subtropical air to the south, and is the path along which rain and snow-bearing low pressure systems ride. Instead of blowing straight west-to-east, the jet stream often contorts itself into a wave-like pattern. Where the jet stream bulges northwards into a ridge of high pressure, warm air flows far to the north. Where the jet loops to the south into a trough of low pressure, cold air spills southwards. The more extreme these loops to the north and south are--the amplitude of the jet stream--the slower the waves move eastward, and consequently, the more persistent the weather conditions tend to be. A high-amplitude jet stream pattern (more than 1000 miles or 1610 km in distance between the bottom of a trough and the peak of a ridge) is likely to bring abnormally high temperatures to the region under its ridge, and very cold temperatures and heavy precipitation underneath its trough. The mathematics governing atmospheric motions requires that higher-amplitude flow patterns move more slowly. Thus, any change to the atmosphere that increases the amplitude of the wave pattern will make it move more slowly, increasing the length of time extreme weather conditions persist. Dr. Francis discovered that during the early 1960s, a natural pattern in the atmosphere called the Arctic Oscillation increased the amplitude of the winter jet stream pattern over North America and the North Atlantic by more than 100 miles, increasing the potential for long-lasting weather conditions. The amplitude of the winter jet fell over 100 miles (161 km) during the late 1960s, remained roughly constant during the 1970s - 1990s, then increased by over 100 miles again during the 2000s. This latest increase in wave amplitude did not appear to be connected to the Arctic Oscillation, but did appear to be connected to the heating up of the Arctic due to sea ice loss. A warmer Arctic allows ridges of high pressure to build farther to the north. Since temperatures farther to the south near the bases of the troughs are not changing much by comparison, the result is that the amplitude of the jet stream grows as the ridges of high pressure push farther to the north. Thus it is possible that Arctic sea ice loss and the associated increases in jet stream amplitude could be partially responsible for some of the recent unusual extreme weather patterns observed in the Northern Hemisphere. This is preliminary research that has yet to be published, and much more work needs to be done before we can confidently link Arctic sea ice loss with an increase in extreme weather, though.


Figure 4. A high-amplitude jet stream pattern observed over the U.S. on December 13, 2011. Instead of blowing straight west-to-east, the jet was contorted into a southward-bulging trough of low pressure that brought cold temperatures and a snow storm to Southern California, and a northwards-bulging ridge of high pressure that brought record warm temperatures to portions of the eastern 2/3 of the country. The axis of the jet stream is marked by the strongest winds (green and light blue colors) at the top of the lower atmosphere (200 - 300 mb pressure level.)

Earlier snow cover melt on Arctic land also increases the amplitude of jet stream troughs and ridges
As Earth's climate has warmed over the past 30 years, the Northern Hemisphere has seen a dramatic drop in the amount of snow cover in spring (April, May, and June.) Spring is coming earlier by an average of three days per decade, and the earlier arrival of spring has significantly reduced the amount of snow on the ground in May. Less snow on the ground means the land surface can heat up more readily, and May temperatures in Arctic have increased significantly over the past 30 years. Dr. Francis found that the upper-level wave amplitude has increased by over 100 miles (161 km) in summer over the past decade, and this change appears to be connected to the decline in May snow cover. Thus, reduced May snow cover due to global warming may be causing higher-amplitude jet stream patterns, potentially leading to slower-moving weather patterns that favor extreme weather in summer, such as heat waves, drought, and flooding. Note that significant changes to the upper-level atmospheric circulation in spring were not observed, so springtime extreme weather events like the 2011 flooding and tornadoes in the U.S. cannot be connected to changes in the Arctic sea ice or high-latitude snow cover using this research.

Related posts
Florida shivers; Hot Arctic-Cold Continents pattern is back
Jet stream moved northwards 270 miles in 22 years; climate change to blame?

Jeff Masters

Climate Change Extreme Weather Arctic

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Tropical Storm Lee's flood in Binghamton: was global warming the final straw?

By: JeffMasters, 3:55 PM GMT on December 14, 2011

With one of the wildest weather years in U.S. history drawing to a close, it's time to look back at some of this year's unprecedented onslaught of billion-dollar weather disasters--and the lessons we should have learned. One of these disasters was the approximately $1 billion in damage due to flooding from Tropical Storm Lee, which brought torrential rains along a swath from Louisiana to New York in early September. Among the hardest hit cities was Binghamton, New York (population 47,000), where record rains due to the remnants of Tropical Storm Lee on September 8 brought a 1-in-200 to 1-in-500 year flood to the city's Susquehanna River. A flood 8.5 inches higher than the city's flood walls spilled over into the city that day, damaging or destroying over 7,300 buildings in Greater Binghamton, and causing hundreds of millions of dollars in damage. Damage to Binghamton's sewage treatment plant and city infrastructure alone are estimated at $26 million. Damage to one elementary school is estimated at $11 - 19 million. The total damage to the county Binghamton lies in (Broome) and the downstream Tioga County is estimated at $1 billion. I argue that there is strong evidence that the extra moisture that global warming has added to the atmosphere over the past 40 years could have been "the straw that broke the camel's back" which allowed Binghamton's flood walls to be overtopped, causing tens of millions in damages. Had this event occurred 40 years ago, before global warming added an extra 4% moisture to the atmosphere, the Susquehanna flood would have likely stayed within the city's flood walls.


Figure 1. Front Street Bridge on the Susquehanna River in Vestal, NY, immediately following the flood of September 8, 2011. Image credit: USGS, New York.


Figure 2. The Susquehanna River at Binghamton crested on September 8, 2011, at the highest flood height on record, 25.71'. The previous record flood was 25', set June 28, 2006. Flood records in Binghamton go back to 1846. Image credit: NOAA/AHPS.


Figure 3. Damage survey of Binghamton, New York after rains from the remains of Tropical Storm Lee sent the Susquehanna River over the city's flood walls on September 8, 2011. Image credit: City of Binghamton.

Binghamton's 2nd 1-in-200-year+ flood in five years
This year's flood is the second 1-in-200 to 1-in-500 year flood in the past five years to hit Binghamton. On June 26 - 29, 2006, tropical moisture streaming northwards over a front stalled out over New York state brought over thirteen inches of rain to portions of southern New York. The Susquehanna River swelled to record levels, triggering devastating flooding that cost at least $227 million. In Binghamton, the Susquehanna River crested eleven feet over flood stage, the greatest flood since records began in 1846. The flood walls protecting Binghamton were overtopped by a few inches, allowing water to pour into the city and cause tens of millions of dollars in damage. This flood is another example of a case where global warming may have been "the straw that broke the camel's back", allowing the flood walls to be overtopped by a few inches. While it is not impossible that the 2006 flood and the 2011 flood could have occurred naturally so close together in time, such a rare double flood has been made more likely by the extra moisture added to the atmosphere due to global warming.


Figure 4. Susquehanna River floodwaters overtop a flood wall along North Shore Drive, Binghamton, NY, on June 28, 2006. Photo courtesy of Alan A. Katz, and available in the USGS report, Flood of June 26 - 29, 2006, Mohawk, Delaware, and Susquehanna River Basins, New York.

The 2011 Tropical Storm Lee flood event on the Susquehanna: a convergence of rare events
Near-record rains fell over much of New York, Pennsylvania, and surrounding states during the first four weeks of August 2011, thanks to an active weather pattern that brought numerous thunderstorms. By August 27, Binghamton, New York had already received nearly double its normal total of 3.45" of rain for the month. When Hurricane Irene swept northwards along the mid-Atlantic coast on August 28, the storm dumped record rains that triggered billions of dollars in flood damage. The Susquehanna River Valley and Binghamton were spared the heaviest of Irene's rains and suffered only minor flooding, but the region received 3 - 5 inches of rain, saturating the soils. The 2.72 inches of rain that fell on Binghamton brought the total rainfall for August 2011 to 8.90", making it the rainiest August in city history (weather records go back to 1890.) Irene's rains helped give New York, New Hampshire, New Jersey, and Vermont their wettest Augusts since record keeping began in 1895.


Figure 5. Rainfall amounts from Hurricane Irene ranged from 3 - 5 inches over Binghamton and the Susquehanna River Valley upstream (northeast) of the city. Image credit: David Roth, NOAA/HPC.


Figure 6. Rainfall amounts from Hurricane Lee ranged from 5 - 10 inches over Binghamton and the Susquehanna River Valley upstream (northeast) of the city. Image credit: David Roth, NOAA/HPC.

Irene set the stage for what was to become the greatest flood in recorded history on the Susquehanna River. On September 5, a front stalled out over Pennsylvania and New York. Tropical moisture streaming northwards in advance of Tropical Storm Lee was lifted up over the front, and heavy downpours resulted. The rains continued for four days, and were amplified by the arrival of Tropical Storm Lee's remnants on September 7, plus a stream of moisture emanating from far-away Hurricane Katia, 1,000 miles to the south-southeast. Binghamton, New York received 8.70" of rain in 24 hours September 7 - 8, the greatest 24-hour rainfall in city history. This was nearly double the city's previous all-time record (4.68" on Sep 30 - Oct. 1, 2010.) The record rains falling on soils still saturated from Hurricane Irene's rains ran off rapidly into the Susquehanna River, which rose an astonishing twenty feet in just 24 hours. By noon on September 8, the rampaging Susquehanna River crested in Binghamton at 25.71', the highest level since records began in 1846. The river would have risen higher had the city's flood walls been higher, but since the water was overtopping the flood walls and spreading out over the city, the river was limited to how high it could rise. By month's end, precipitation in Binghamton for September 2011 totaled 16.58", more than thirteen inches above normal, making it Binghamton's wettest month since records began in 1890.

We can thus see how the record Susquehanna River flood of September 8, 2011 was due to a convergence of rare events, which included moisture from three tropical cyclones:

1) The unusually heavy rains during the first four weeks of August, before the arrival of Hurricane Irene.

2) Hurricane Irene's 3 - 5 inches of rain.

3) The extreme rains from Tropical Storm Lee's remnants.

4) The enhanced rainfall on September 7 - 8 due to a moisture plume from Hurricane Katia.

Had any one of these events not occurred, it is questionable whether the flood walls in Binghamton would have been overtopped. One could also argue that the flood walls would not have been overtopped had there been less development in the Susquehanna's floodplain. Dr. Peter Knuepfer, Associate Professor of Geology and director of the Environmental Studies Program at Binghamton University, and Dr. Burrell Montz, who is now Professor and Chair of Geography at East Carolina University, wrote in a 2007 essay titled, Flooding and Watershed Management, "the 2006 flood might be considered a land use flood, due to the levels of development in floodplains in Conklin and elsewhere in the Binghamton area." They argued that development on the Susquehanna's floodplain has been driven by economics, without enough thought to how development increases flood heights downstream. "It can hardly be argued that we need to reacquaint the river with its floodplain," they concluded. In an email I received from Dr. Knuepfer, he indicated that some positive steps have been taken to reduce flood vulnerability in the Binghamton area before this year's flood: "There's still more development in the floodplain than should be, though there is a little more awareness (but only a little!) about the downstream implications of raising levees and walls (and certainly this seems to be true at the Federal level). From Binghamton downstream--the Susquehanna River had a 200+ year flood (the number one chooses depends on how one treats the historic flood record, but it was clearly an event well beyond the historical record.) Some areas flooded by the river in 2006--houses, specifically--no longer exist due to FEMA buy-outs. Yet there is still development in flood-prone areas, so there is still a degree of floodplain development that contributes significantly to the disaster. On the other hand, this flood overtopped levees and flood walls precisely because it was a bigger natural event than these were designed to withstand. So there's still more exposure than I'd like to see, but this was a natural disaster." To illustrate how development in a flood plain can increase flood height, consider this stat from nrdc.org: a 1-inch rainstorm falling on a 1-acre natural meadow produces about 28 bathtubs full of runoff into local rivers. However, a 1-inch rainstorm falling on a 1-acre parking lot produces sixteen times as much runoff--448 bathtubs full. We obviously can't convert our parking lots into meadows, but we can create permeable pavement, planted swales around parking lots, rain gardens planted along sidewalks, green roofs, and more trees to help absorb rainwater like a sponge. The city of Philadelphia has recently started an ambitious effort to reduce flood through such green infrastructure efforts.


Figure 7. Water vapor satellite image taken at 2:45 pm EDT September 7, 2011, during the height of the heavy rainstorm affecting the Susquehanna River Valley near Binghamton, NY. Moisture came from the remains of Tropical Storm Lee, tropical moisture streaming northwards and lifting over a stalled front, and from Hurricane Katia, located 1,000 miles to the south-southeast, between Florida and Bermuda. White and blue colors show where copious atmospheric moisture lies, while brown colors show dry air. Image credit: NOAA/NESDIS.

The global warming connection
Finally, I'll add one more "straw that broke the camel's back" that contributed to the overtopping of the flood walls in Binghamton: global warming. Had the flood of September 8, 2011 occurred in the atmosphere of the 1970s or earlier, the flood walls would have been less likely to be overtopped. There is a well-established relationship in atmospheric physics called the Clausius-Clapeyron equation, which says that atmospheric moisture will increase by 6% - 7% for every degree Centigrade increase in Earth's temperature. Global sea surface temperatures in the regions where hurricanes form, between 30°S and 30°N latitude, warmed 0.9°F (0.5°C) between 1970 - 2004, due to global warming (Trenberth et. al, 2007.) Satellite observations show that atmospheric moisture over the oceans increased by 1.3% per decade between 1988 - 2003 (Trenberth, 2006), so we can expect that the amount of moisture storms have to work with has increased by 4% since 1970 and 5% since 1900 (IPCC, 2007.) The amount of rainfall a hurricane can now drop as a result of this increase in moisture can be much more than 4 - 5%, though. The extra moisture in the atmosphere helps intensify storms by releasing "latent heat" energy when it condenses into rain. Latent heat is the extra energy that is required to convert liquid water to gaseous water vapor, and this energy is liberated when the vapor condenses back to rain. The released latent heat energy invigorates the updrafts in a storm, allowing it to draw in moisture from an area greater than usual (a typical storm draws in moisture from an area 3 - 5 times the radius of the precipitating region, according to Trenberth et.al, 2003.) This effect is thought to be the main reason why heavy precipitation events--the ones most likely to cause floods--have been increasing over the past 50 years, in general agreement with the predictions of climate models (Figure 8.) A 2008 study in the Netherlands by Lenderink and Meijgaard called "Increase in hourly precipitation extremes beyond expectations from temperature changes," found that "one-hour precipitation extremes increase twice as fast with rising temperatures as expected from the Clausius–Clapeyron relation when daily mean temperatures exceed 12°C. In addition, simulations with a high-resolution regional climate model show that one-hour precipitation extremes increase at a rate close to 14% per degree of warming in large parts of Europe." A 2007 study led by Dr. Kevin Trenberth of the National Center for Atmospheric Research, "Water and energy budgets of hurricanes: Case studies of Ivan and Katrina", looked at how much additional rainfall hurricanes might be dropping as a result of global warming. The researchers found that global warming likely increased the amount of rain dropped Hurricane Ivan and Hurricane Katrina by 6 - 8%. The authors wrote, "We conclude that the environmental changes related to human influences on climate have very likely changed the odds in favor of heavier rainfalls and here we suggest that this can be quantified to date to be of order 6 to 8% since 1970. It probably also results in more intense storms. The key point is that the value is not negligible, and nor is it large enough to dominate over the natural processes already in place. In the case of Katrina and New Orleans, where rainfalls locally exceeded 12 inches (305 mm), this would mean an enhancement of about 0.75 to 1 inch (19 to 25 mm). Although incremental, such changes can cause thresholds to be exceeded (the straw that breaks the camel's back.) Small differences of a few percent in rainfall can matter a great deal when that extra water is concentrated by a river drainage system to create a flood. For example, observations of flooding events in the Pennsylvania's 7.2 square km Mahantango Creek watershed (Troch et al., 1993) showed one case where two rainfall events with the same maximum precipitation rate generated flow rates in the creek a factor of seven different, even though the difference in total precipitation between the two events was about a factor of two. A modeling study by Jha et al. (2004) predicted that climate change would cause a 21% annual increase in precipitation over the Upper Mississippi River basin by 2040. However, their model predicted that streamflow would increase much more than this--51%. This occurred as a result of rain falling on saturated soils, which creates disproportionately large runoff. Much of the rain falling on dry soils takes time to infilrate the soil, and the arrival of this water into a river is delayed. But if soils are saturated, a greater percentage of the rain runs off immediately into the river, resulting in higher stream flows and higher flood potential. The largest increases in streamflow in their model occurred in spring and summer, when flood danger is at its highest.


Figure 8. Percent increase in the amount falling in heavy precipitation events (defined as the heaviest 1% of all daily events) from 1958 to 2007, for each region of the U.S. There are clear trends toward more very heavy precipitation events for the nation as a whole, and particularly in the Northeast and Midwest. Climate models predict that precipitation will increasingly fall in very heavy events in coming decades. Image credit: United States Global Change Research Program. Figure updated from Groisman, P.Ya., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004: Contemporary changes of the hydro-logical cycle over the contiguous United States, trends derived from in situ observations. Journal of Hydrometeorology, 5(1), 64-85.

Conclusion
There is strong evidence that the extra moisture that global warming has added to the atmosphere over the past 40 years could have been "the straw that broke the camel's back" in the case of the Susquehanna River floods of June 2006 and September 8, 2011, which overtopped the flood walls in Binghamton, New York, causing tens of millions of dollars in damages. During September 8, 2011 flood, the Susquehanna River rose twenty feet in 24 hours and topped the flood walls in Binghamton by 8.5 inches, so just a 6% reduction in the flood height would have led to no overtopping of the flood walls and a huge decrease in damage. Extra moisture in the air due to global warming could have easily contributed this 6% of extra flood height. It is possible that detailed computer modeling studies of the event may conclude that global warming was not a significant factor in this particular case, but we will see an increasing number of these back-breaking extreme flooding events in the future as the climate continues to warm and we increasingly load the dice in favor of greater extreme rainfall events. It is wildly improbable that two 1-in-200 to 1-in-500 year floods could have occurred on the same river within five years of each other naturally. Increased moisture in the atmosphere due to global warming and increased flood plain development are shifting the odds in favor of more extreme floods occurring more often. Our flood control system, which is designed for the climate of the 20th century and a lesser degree of flood plain development, is bound to be increasingly overwhelmed if we continue to put more structures into flood plains and continue to pump more heat-trapping carbon dioxide into the atmosphere. Unfortunately, we are not dealing well with the "new normal" for extreme floods. The National Flood Insurance Program, which charges unrealistically low insurance premiums, is $18 billion in debt. A government shut-down was narrowly avoided in September over disputes on how to pay for the damages from this year's 1-in-100 to 1-in-500 year floods on the Mississippi, Missouri, Ohio, Souris, Susquehanna, and hundreds of smaller rivers. Federal funding to operate 321 USGS stream gauges critical for issuing accurate and timely flood warnings was eliminated this year, and funding for an additional 69 gauges is threatened, including gauges on the Susquehanna River where this year's extreme flooding occurred. Eliminating funding for stream gauges in an era of increasing floods is like being too cheap to replace your cracked windshield that's hard to see out of, when you're about to drive the most difficult and dangerous road your car has ever attempted, at night, in a heavy rainstorm. You'll be unaware of the coming danger until it's too late to avoid it. Flood damages are going to grow much worse and potentially cause serious harm to the American economy in the coming decades, and our politicians need to adopt intelligent policies that don't cater to special interests in order to deal with the increasingly frequent and larger extreme floods that a warmer climate will bring.

References
IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Jha, M., Z. Pan, E. S. Takle, and R. Gu (2004), Impacts of climate change on streamflow in the Upper Mississippi River Basin: A regional climate model perspective, J. Geophys. Res., 109, D09105, doi:10.1029/2003JD003686.

Lenderink, G., and E. van Meijgaard (2008), Increase in hourly precipitation extremes beyond expectations from temperature changes,, Nature Geoscience 1, 511 - 514 (2008)
Published online: 20 July 2008 | doi:10.1038/ngeo262

Suro, T.P., G.D. Firda, and C.O. Szabo, 2009, Flood of June 26 - 29, 2006, Mohawk, Delaware, and Susquehanna River Basins, New York, USGS Open-File Report 2009-94-1063.

Trenberth, K. E., A. Dai, R. M. Rasmussen and D. B. Parsons, 2003: The changing character of precipitation", Bull. Amer. Meteor. Soc., 84, 1205-1217.

Trenberth, K. E., C. A. Davis and J. Fasullo, 2007: "Water and energy budgets of hurricanes: Case studies of Ivan and Katrina," J. Geophys. Res., 112, D23106, doi:10.1029/2006JD008303.

Trenberth, K.E., J. Fasullo, and L. Smith. 2005. "Trends and variability in column-integrated atmospheric water vapor," Climate Dynamics 24:741-758.

Trenberth, K. E., 2011: Changes in precipitation with climate change. Climate Research, 47, 123-138,
doi:10.3354/cr00953.

Troch, P.A., J.A. Smith, E.F. Wood, and F.P. de Troch, "Hydrologic Controls of Large Floods in a Small Basin: Central Appalachian Case Study", Journal of Hydrology, 156:285-309, 1994.

Other posts looking back at the remarkable weather events of 2011
Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.
Hurricane Irene: New York City dodges a potential storm surge mega-disaster

Jeff Masters

Climate Change Flood

Updated: 2:41 PM GMT on March 09, 2012

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Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.

By: JeffMasters, 3:00 PM GMT on December 12, 2011

This year is now the wettest year in nearly 200 years of record keeping in Philadelphia, Pennsylvania. A large, wet low pressure system soaked the Northeast U.S. on Wednesday and early Thursday, bringing 2.31 inches of rain to the City of Brotherly Love, bringing this year's precipitation total in Philly to 62.26 inches. This breaks the old yearly precipitation record of 61.20 inches, set in 1867. In a normal year, Philadelphia receives about 40 inches. According to wunderground's weather historian Christopher C. Burt, this is one of the most difficult U.S. city records to break, since rainfall records in Philadelphia go back to 1820. The only other sites with a longer continuous precipitation record in the U.S. are Charleston, SC (1738 -) and New Bedford, MA (1816 -).


Figure 1. Departure of precipitation from average for 2011, as of December 6, 2011. Image credit: NOAA/HPC.

20+ inches above average precipitation in Ohio Valley, Northeast
Philadelphia is not alone in setting a wettest year in recorded history mark in 2011. Over a dozen major cities in the Ohio Valley and Northeast have set a new wettest year record, or are close to doing so. Thanks to rains associated with this year's tremendous tornado outbreaks in April in May, plus exceptionally heavy summer thunderstorm rains, combined with rains from Tropical Storm Lee and Hurricane Irene, portions of at least twelve states have seen rains more than twenty inches above average during 2011.



The fraction of the country covered by extremely wet conditions (top 10% historically) was 32% during the period January through November, ranking as the 2nd highest such coverage in the past 100 years. And if you weren't washing away in a flood, you were baking in a drought in 2011--portions of sixteen states had precipitation more than twenty inches below average (Figure 1.) The fraction of the country covered by extremely dry conditions (top 10% historically) was 22% during the period January through November, ranking as the 8th highest in the past 100 years. The combined fraction of the country experiencing either severe drought or extremely wet conditions was 56% averaged over the January - November period--the highest in a century of record keeping. Climate change science predicts that if the Earth continues to warm as expected, wet areas will tend to get wetter, and dry areas will tend to get drier--so this year's side-by-side extremes of very wet and very dry conditions should grow increasingly common in the coming decades.


Figure 2. Percentage of the contiguous U.S. either in severe or greater drought (top 10% dryness) or extremely wet (top 10% wetness) during the period January - November, as computed using NOAA's Climate Extremes Index. Remarkably, more than half of the country (56%) experienced either a top-ten driest or top-ten wettest year, a new record. Image credit: NOAA/NCDC.

Unofficial state yearly precipitation record set in Ohio
The Wilmington, Ohio NWS office announced last week that three stations in Southwest Ohio had unofficially broken the 140-year old state yearly precipitation record. Cheviot, Miamitown, and Fernbank have recorded 73.81", 71.89", and 70.85", respectively so far in 2011, beating the old record of 70.82" set at Little Mountain in 1870. According to wunderground's weather historian Christopher C. Burt, the old record should be 72.08” at Mt. Healthy, Ohio in 1880.

Wunderground's weather historian Christopher C. Burt summarizes the global weather extremes in November in his latest post.

Jeff Masters

Extreme Weather Drought Flood

Updated: 3:10 PM GMT on December 12, 2011

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Watch out for the bugs

By: JeffMasters, 12:56 AM GMT on December 10, 2011

I'm wrapping up my stay in San Francisco for the annual Fall Meeting of the American Geophysical Union (AGU), the world's largest gathering of Earth Scientists. Over eighteen thousand scientists from all over the world, including most of the world's top climate scientists, were in town this week to exchange ideas to advance the cause of Earth Science. It's been a great opportunity to learn about climate change topics I don't know much about, and I attended a fascinating (and somewhat unnerving) lecture on how global warming is expected to affect insects, titled "The Impact of Global Warming on global crop yields due to changes in pest pressure". Global warming is expected to bring a variety of impacts to agriculture, both positive and negative. Extra CO2 in the atmosphere will tend to increase crop yields, but crop losses due to insect pests are expected to double by 2100, according to a insect pest/crop model designed by David Battisti of the University of Washington. These losses will occur in addition to the expected 35 - 40% decrease in crop yields due to higher temperatures by the end of the century.



When temperature increases, the metabolic rate of insects goes up, requiring that they eat more to survive. In the mid-latitudes, the predicted 2 - 4°C temperature increase by 2100 will require insects to eat double what they do now, in order to survive. The increase in temperature is also expected to enable insect populations to rise by 20%. However, insect populations will fall by 20% in the tropics, where insects have evolved to tolerate a much narrower range of temperatures. Let's look at the world's three most important crops: rice, wheat, and corn. In the four largest rice producing countries--China, India, Bangladesh, and Thailand--Insects currently cause a loss of 10- 20% of the crop, and this is expected to double to 20 - 30% by 2100. These nations have 40% of the world's population, and make 60% of the world's rice. For corn, the world's four largest producers--the U.S., China, France, and Argentina--are expected to see insect pest losses double from 6% to 12%. The story is similar for wheat; pest losses are expected to double from 10% to 20% by 2100. The total increased damage to global agriculture is predicted to be $30 - $50 billion per year by 2100. This will likely contribute greatly to food costs and potential food shortages. The model made a number of simplifications that could greatly change this outcome, though. The model assumed that there would be no change to the number of insects that survive winter, and this number is likely to increase in a warmer climate. Precipitation was not changed to reflect what is expected to happen in a changed climate, and this will cause increases in crop yields in some areas, and decreases in others. Farmers are likely to change growing practices and utilize new pesticides to combat the expected increase in pests, and this was not considered, either. It is interesting to note that during the great natural global warming event of 55 million years ago--the Palecene-Eocene Thermal Maximum (PETM)--fossil records of plant leaves show greatly increased levels of damage from insects, supporting the idea that a warmer climate will drive an explosion in the insect population.

Jeff Masters

Climate Change

Updated: 12:59 AM GMT on December 10, 2011

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Twelve U.S. billion-dollar weather disasters in 2011 so far: NOAA

By: JeffMasters, 6:11 PM GMT on December 08, 2011

The official tally of billion-dollar U.S. weather disasters in 2011 is now twelve, announced NOAA administrator Jane Lubchenco in a speech given yesterday at the American Geophysical Union meeting in San Francisco. This is the greatest number of billion-dollar weather disasters in U.S. history, besting the record of nine set in 2008. Dr. Lubchenco said that at least two additional disasters, the October 29 snowstorm in the Northeast, and the flooding from Tropical Storm Lee in early September, may surpass the $1 billion mark, by the time all damage estimates are tabulated. This would bring the 2011 tally to fourteen billion-dollar weather disasters, a truly astonishing level of destruction for one year. The damages from the twelve official billion-dollars disasters is $52 billion, making the 2011 the 4th most expensive year for billion-dollar weather disasters in history. Damage estimates from natural disasters are fraught with uncertainty, and it is not usual for different insurance companies to give damage estimates a factor of two different for the same disaster. Insurance broker AON Benfield estimates that there have been at least sixteen billion-dollar weather disasters in the U.S. so far in 2011, according to their November Catastrophe Recap report. Included in their tally, but not in NOAA's, are severe weather outbreaks on July 10 - 14 and August 18 -19 in the Plains that caused $1.25 billion and $1.1 billion in damage, respectively, plus $1 billion in damage from Tropical Storm Lee's floods, and $3 billion in damage from the October 28 - 30 snowstorm in the Northeast.


Figure 1. Billion-dollar U.S. weather disasters in 2011 as officially recognized by NOAA's National Climatic Data Center in early December, 2011. Image credit: NOAA/NCDC.

Jeff Masters

Extreme Weather

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CSU and TSR predict above average 2012 Atlantic hurricane season

By: JeffMasters, 5:17 PM GMT on December 07, 2011

Above-average Atlantic hurricane activity is likely for 2012, but there is a 40% chance of an El Niño event that will keep hurricane activity below average, according to the latest seasonal forecast issued today by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). For the first time in twenty years, the CSU team is not issuing a December forecast with a specific number of tropical storms and hurricanes. Instead, they have issued a more qualitative forecast, which I think is a great idea, since their quantitative December forecasts have shown no skill. Their outlook for the 2012 Atlantic hurricane season:

15% chance: Very active season with 14-17 named storms, 9-11 hurricanes, 4-5 major hurricanes
45% chance: Active season with 12-15 named storms, 7-9 hurricanes, 3-4 major hurricanes
30% chance: Inactive season with 8-11 named storms, 3-5 hurricanes, 1-2 major hurricanes
10% chance: Very inactive season with 5-7 named storms, 2-3 hurricanes, 0-1 major hurricanes

An average season has 11 named storms, 6 hurricanes, and 2 intense hurricanes. The main reason that CSU's December forecasts have shown no skill is because we have no skill predicting El Niño events nine months or more into the future. When an El Niño event occurs, bringing much above average wind shear over the tropical Atlantic, hurricane activity is substantially reduced. Making successful seasonal hurricane forecasts requires that one make a successful El Niño forecast.


Figure 1. Forecasts of El Niño conditions by 20 computer models, made in November 2011. The longest range forecasts for July-August-September (JAS) at the right side of the image show that 3 models predict weak El Niño conditions, 8 predict neutral conditions, and 1 predicts a weak La Niña. El Niño conditions are defined as occurring when sea surface temperatures in the Equatorial Pacific off the coast of South America (the "Niño 3.4 region) rise to 0.5°C above average (top red line). La Niña conditions occur when SSTs in this region fall to 0.5°C below average (blue line.) Image credit: Columbia University.

What will El Niño do in 2012?
We currently have a borderline weak to moderate La Niña episode in the Eastern Pacific, characterized by cooler than average waters off the equatorial coast of South America. While we can say with good confidence that La Niña will continue through the winter and into spring, it is highly uncertain what might happen next summer and fall to La Niña. In April and May, we typically see La Niña fade to neutral, and in many cases, a full-blown El Niño will develop by the fall. As the CSU team notes, there have been fourteen years since 1950 which had La Niña conditions that were similar to what we are experiencing this December. During the following years' hurricane season, an El Niño event developed 36% of the time, in those fourteen years. In 2012, the odds of a fall El Niño may be higher than this, since we have gone three years since the last El Niño, and these events typically occur every 3 - 7 years. Of the 12 El Niño/La Niña computer models that made November predictions for the July-August-September 2012 portion of hurricane season (Figure 1), only 3 (20%) predicted that El Niño would arrive. However, these models have no skill predicting El Niño so far in advance.

2012 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issued their 2012 Atlantic hurricane season forecast today. TSR is calling for an above-average year, with 14.1 named storms, 6.7 hurricanes, and 3.3 intense hurricanes. TSR predicts a 49% chance of an above-average hurricane season, 30% chance of a near-normal season, and a 21% chance of a below normal season. TSR bases their December forecast on predictions that sea surface temperatures next fall in the tropical Atlantic will be above about 0.1°C above average, and trade wind speeds will be about 0.2 m/s slower than average. The trade wind speed prediction is based on a forecast for neutral El Niño conditions in August - September 2012.

I like how TSR puts their skill level right next to the forecast numbers: 3% skill above chance at forecasting the number of named storms, 0% skill for hurricanes, and 7% skill for intense hurricanes. That's not much skill, and really, we have to wait until the June 1 forecasts by CSU, NOAA, and TSR to get a forecast with reasonable skill.


Figure 2. Forecast skill of the TSR, NOAA (National Oceanic and Atmospheric Administration) and CSU (Colorado State University) seasonal hurricane outlooks 2002-2011 as a function of lead time. NOAA does not release seasonal outlooks before late May. It is clear there is little skill in forecasting the upcoming number of Atlantic hurricanes from the prior December. Skill climbs slowly as the hurricane season approaches. Moderate skill levels are reached by early June and good skill levels are achieved from early August. Image credit: Tropical Storm Risk, Inc (TSR).

Jeff Masters

Hurricane

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Climate change education in zoos

By: JeffMasters, 5:20 PM GMT on December 05, 2011

I'm in San Francisco this week for the annual Fall Meeting of the American Geophysical Union (AGU), the world's largest gathering of Earth Scientists. Over ten thousand scientists from all over the world, including most of the world's top climate scientists, are in town this week to exchange ideas to advance the cause of Earth Science. This year, there is much attention being given to communication of science to the public, and the first talk I attended today on the subject was given by Dr. Michael Mann of Penn State University. Dr. Mann has been at the center of much recent controversy over climate science, and has an op-ed in today's Wall Street Journal titled, "Climate Contrarians Ignore Overwhelming Evidence". His "hockey stick" graphs showing the unprecedented increase in global temperatures over the past 1,000 years has been the subject of heated attack, much of it orchestrated by the public relations wings of powerful industries whose profits are threatened by by possibility of regulatory action to reduce global warming. He has a book coming out in January titled, The Hockey Stick and the Climate Wars: Dispatches from the Front Lines. Dr. Mann reaffirmed his stance on human-caused climate change in his talk this morning, calling attention to a paper that appeared in Nature Geoscience last week, finding that most of the observed warming of Earth's climate in recent decades—at least 74 percent—is almost certainly due to human activity. Dr. Mann said that this study did not go far enough, and that more than 100% of the warming in the past 30 years was due to humans. Without humans, the climate would have cooled over the past 30 years.


Figure 1. An example of educational material on polar bears that has been developed by CliZEN for use at nine U.S. zoos.

Dr. Mann also introduced a new pilot program he is involved with to advance climate change education through U.S. zoos. The National Science Foundation-funded project is called CliZEN, The Climate Literacy Zoo Education Network. Zoos represent a unique way for people to connect to the natural world, and over 50 million people in the U.S. go to the zoo each year--double that, if one includes aquariums. Thus, zoos thus offer a unique opportunity to communicate how climate change threatens the natural world. People who go to zoos are approximately 50% more likely to be alarmed or concerned about climate change than the general population, Dr. Mann showed. The initial eduction effort has a polar theme, and is being brought to nine zoos: the Chicago Zoological Society of Brookfield, IL; Columbus Zoo & Aquarium, OH; Como Zoo & Conservatory, St. Paul, MN; Indianapolis Zoo, IN; Louisville Zoological Garden, KY; Oregon Zoo, Portland, OR; Pittsburgh Zoo & PPG Aquarium, PA; Roger Williams Park Zoo, Providence, RI; and the Toledo Zoological Gardens, OH. The organization Polar Bears International is helping develop the educational material.

Jeff Masters

Climate Change

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The City That Plans to be Flooded

By: Douglas Hill , 2:22 PM GMT on December 02, 2011

A guest post by Douglas Hill, a consulting engineer and an adjunct lecturer at the School of Marine and Atmospheric Sciences at Stony Brook University in New York.

Hurricane Irene, remember? Irene, diminished to a mere tropical storm when it struck New York City, came and went, soon disappearing from the news. But think back to August 26 when Irene, a Category 3 hurricane with winds of more than 110 miles per hour, was approaching the North Carolina coast and headed directly for New York City. Mayor Michael R. Bloomberg called a news conference to order 370,000 people to evacuate their homes. Then he stepped aside, and MTA chairman Jay Walder stepped to the microphone and announced that public transportation--buses as well as trains--was being shut down.


Figure 1. GOES-East visible satellite image of Irene taken at 7:45 am EDT on Sunday, August 28, 2011. At the time, Irene was a tropical storm with 65 mph winds, making landfall on Long Island, New York. Image credit: NOAA Environmental Visualization laboratory.

Evacuation without transportation: a novel concept that the mayor described as "preparing for the worst and hoping for the best." Fortunately, hoping for the best worked.

Unfortunately, the City is still hoping for the best, and it is not preparing for the worst. The coastal storm plan of the Office of Emergency Management (OEM) includes strategies for storm tracking, public information, evacuation procedures, people with special needs, recovery, and restoration, but nothing to prevent flooding.

In other words, New York City is planning to be flooded--and according to the National Hurricane Center, it will be. Based on the historical record, hurricanes of Categories 1, 2 and 3 will strike the New York region on an average of every 17, 39 and 68 years, respectively. The City has been overdue for a Category 1 hurricane--Irene should have been no surprise--and we may expect hurricanes of Categories 2 and 3 within the next decade or two. In testimony to a U.S. Senate committee, Max Mayfield, the former director of the National Hurricane Center, said, "It is not a question of if a major hurricane will strike the New York area, but when" (his emphasis.)

The greatest potential for loss of life from a hurricane has historically been from the storm surge. If the eye of a Category 3 hurricane crossed the New Jersey shore, the surge could reach 24 feet--compared with 4.5 feet in Hurricane Irene's--flooding the World Trade Center site and Wall Street, with City Hall resting on a separate island south of the rest of Manhattan. The ripples from a crippled financial district in lower Manhattan would be felt worldwide. In a severe hurricane, the OEM has estimated that up to three million people would have to evacuate, if that can be imagined.



Figure 2. The height above ground that a mid-strength Category 2 hurricane with 100 mph winds would push a storm surge into New York City in a worst-case scenario. The image was generated using the primary computer model used by the National Hurricane Center (NHC) to forecast storm surge--the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model. The accuracy of the SLOSH model is advertised as plus or minus 20%. This "Maximum Water Depth" image shows the water depth at each grid cell of the SLOSH domain. Thus, if you are inland at an elevation of ten feet above mean sea level, and the combined storm surge and tide (the "storm tide") is fifteen feet at your location, the water depth image will show five feet of inundation. This Maximum of the "Maximum Envelope of Waters" (MOM) image was generated for high tide and is a composite of the maximum storm surge found for dozens of individual runs of different Category 2 storms with different tracks. Thus, no single storm will be able to cause the level of flooding depicted in this SLOSH storm surge image. Consult wunderground's Storm Surge Inundation Maps page for more storm surge images of the U.S. coast.

Other major ports have taken measures to prevent being flooded. After the 1938 hurricane, storm surge barriers were built in New England to protect New Bedford, Providence and Stamford. After a disastrous storm in the North Sea in 1953, the Thames Barrier was built to protect London, and the Delta Plan was started in the Netherlands which includes three such barriers, one protecting Rotterdam, Europe's busiest port. Following Hurricane Katrina, a long-disputed barrier was constructed at the entrance to Lake Pontchartrain along with several others, which are now considered to make New Orleans hurricane-proof to Category 3 storms. Barriers are being completed to protect St. Petersburg, Russia, and Venice, Italy.

The heart of New York City could be protected in the same way. Moveable barriers, closed only when the city is threatened with major coastal flooding, could be placed at the upper end of the East River, across the Narrows and at the mouth of the Arthur Kill. Possibly, the latter two could be replaced with a single, longer barrier extending from Sandy Hook to the Rockaway peninsula. Modeling studies have demonstrated that the barriers would work. Four major engineering firms have presented conceptual designs and cost estimates for barriers at these locations. The estimated costs for these individual barriers range from $1 billion to $4.6 billion, with the total of the two or three needed less than $10 billion, comparable to other major infrastructure projects planned or underway.


Figure 3. Proposed hurricane storm surge barrier for New York City near the Verrazano Narrows Bridge. Image credit: Arcadis, Inc.

But unlike the original, the 2010 revision of plaNYC, the City's principal planning document, makes no reference to storm surge barriers. The City's latest plans are seen in the March 2011 Vision 2020: NYC Comprehensive Waterfront Plan, which calls not for protecting the waterfront, but for climate "resilience," the ability to withstand and recover from the disaster. Unfortunately, this may be the best that can be done for those living in the coastal sections of the boroughs that face the Atlantic Ocean.

So the Great Evacuation of August 2011 is a test. In its postmortem on the storm on September 5, the New York Times concluded that "by almost any measure, the evacuation was a success," but it did not report on the principal measure. How many people were left behind? Unlike New Orleans after Katrina, we won't know by counting the bodies. Not this time, anyway.

Douglas Hill, EngScD, P.E., Stony Brook University

Other posts in this series
Storm surge barriers: the New England Experience
Hurricane Irene: New York City's close call

Hurricane

Updated: 2:23 PM GMT on December 02, 2011

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About

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