Dr. Jeff Masters' WunderBlog

Over 300 dead in historic tornado outbreak; one violent EF-5 tornado confirmed

By: JeffMasters, 3:20 PM GMT on April 29, 2011

Rescuers sifting through the twisted wreckage of countless towns ravaged by Wednesday's historic tornado outbreak continue to uncover bodies today, and the death toll has swollen to over 300 this morning, and may be as high as 319. Hardest hit was Alabama, with at least 213 dead. Tennessee, Mississippi, Georgia, Arkansas, and Virginia are each reporting 11 - 34 deaths. NOAA's Storm Prediction Center logged 211 preliminary reports of tornadoes between 8am EDT Wednesday and 8am Thursday, and 346 reports for the full 4-day period of the outbreak, from April 25 - April 28. Twenty-two of these tornadoes were killer tornadoes; deaths occurred in six states. Damage surveys will take another week to complete, but preliminary surveys indicate that at least one of the tornadoes was an EF-5--the Smithville, Mississippi tornado, which hit at 3:44pm EDT on Wednesday. That tornado killed 13 people and destroyed 166 buildings, and reportedly sucked fire hydrants out of the ground. Some well-built modern 2-story homes that were bolted to their foundations were completely destroyed, leaving only the foundation. This type of damage is characteristic of an EF-5 tornado with 205 mph winds. The Smithville tornado is the first EF-5 tornado in Mississippi since the Candlestick Park tornado of March 3, 1966. Three other tornadoes from Wednesday's outbreak have been given preliminary EF-4 ratings, with winds of 166 - 200 mph. These include the Phil Campbell, AL tornado (26 deaths), the Ringgold, GA tornado (7 deaths), the Tanner, GA tornado (11 deaths), and the Apison, Tennessee tornado (13 deaths, and possibly the same tornado that hit Ringgold.) The violent tornado that ravaged Tuscaloosa and Birmingham, Alabama, killing at least 46 people and injuring 600, has not yet been given an official rating. I expect this tornado will be rated an EF-4 (possibly an EF-5.) This tornado is likely to be the most expensive tornado of all-time, and damage from the April 25 - 28 outbreak is likely rank as the most expensive tornado outbreak in history. The current record is the $3.5 billion price tag, in 2005 dollars, of the April 3 - 4, 1974 Super Outbreak . According wunderground's weather historian, Christopher C. Burt in his post The World's Deadliest Tornadoes, the death toll of 319 makes the April 25 - 28, 2011 tornado outbreak the fourth deadliest tornado outbreak in U.S. history, and the deadliest since 1936. It is the deadliest of the past 50 years, surpassing the April 3 - 4, 1974 Super Outbreak (315 killed) and the 1965 Palm Sunday tornado outbreak (256 killed.)


Figure 1. Still frame from an animation showing the height and extent of the rain columns associated with the thunderstorms that spawned Wednesday's tornadoes. This data, taken from NASA's TRMM satellite, showed that some of these violent storms reached incredible heights of almost 10.6 miles (17 km.) Image credit: NASA/SSAI, Hal Pierce

The 4-day total of preliminary tornado reports of 346 from this outbreak is close to the 323 preliminary tornado reports logged during the massive April 14 - 16 tornado outbreak. That outbreak has 155 confirmed tornadoes so far, making it the largest April tornado outbreak on record, and 3rd largest in history. The numbers from this week's outbreak may be even higher, giving April 2011 the 3rd and 4th largest tornado outbreaks in history, and the deadliest outbreak in 75 years. According to a list of tornado outbreaks maintained by Wikipedia, only two other tornado outbreaks have had as many as 150 twisters--the May 2004 outbreak (385), and the May 2003 outbreak (401).


Figure 2. Storm chaser video from Reed Timmer and tornadovideos.net of four tornadoes that hit Alabama and Mississippi on Wednesday.


Figure 3. Storm chaser video of the tornado that moved through Philadelphia, Mississippi on Wednesday.

Unprecedented flooding predicted on Ohio and Mississippi Rivers
This week's storm system, in combination with heavy rains earlier this month, have pushed the Ohio River and Mississippi River to near-record levels near their confluence. The Ohio River at Cairo, Illinois is expected to crest at 60.5 feet on May 1. This would exceed 100-year flood stage, and be the highest flood in history, besting the 59.5' mark of 1937. Heavy rains of 10 - 15 inches have inundated the region over the past week. Additional rains of 1 - 3 inches are expected over the next five days.


Figure 4. Rainfall for the 7-day period ending at 8am EDT Thursday, April 28, 2011. Image credit: NOAA/AHPS.

Record 100+ year flood expected on Mississippi River
Snow melt from this winter's record snow pack across the Upper Mississippi River has formed a pulse of flood waters that is moving downstream. When this floodwater pulse moves south of Cairo, Illinois over the next two weeks, it will join with the record water flow coming out of the Ohio River, and create the highest flood heights ever recorded on the Mississippi, according to the latest forecasts from the National Weather Service. Along a 400-mile stretch of the Mississippi, from Cairo to Natchez, Mississippi the Mississippi is expected to experience the highest flood heights since records began 100 or more years ago, at 5 of the 10 gauges on the river along this stretch. The records are predicted to begin to fall on May 3 at New Madrid, and progress downstream to Natchez by May 20. Areas that are not protected by levees can expect extensive damage from the flooding, and it is possible that the Army Corps of Engineers will have to intentionally dynamite levees at Birds Point and New Madrid, Missouri to protect the town of Cairo from flooding. One unofficial estimate I saw on the Army Corps of Engineers web site put the cost of intentionally breaching the levees at Birds Point and New Madrid at $100 million dollars, due to damage to the croplands and structures in the flooded area. No levee has failed on the Lower Mississippi south of the Ohio River junction since 1950, and the Army Corp of Engineers has designed the levee system to contain a 500-year flood. This means that the Mississippi River flood of 2011--which will be somewhere between a 100-year and 200-year flood between Cairo and Natchez--is not likely to be a multi-billion-dollar disaster like the 1993 flood on the Upper Mississippi, where many levees failed.

The Mississippi River at New Madrid, MO, about 40 miles downstream of the confluence of the Mississippi and Ohio Rivers, is currently at 44.9', the 2nd highest flood in history. The river is predicted to crest on Tuesday very near the all-time record height of 48 feet. The NWS warns that at this height, "Large amounts of property damage can be expected. Evacuation of many homes and businesses becomes necessary." Previous record heights at this location:

(1) 48.00 ft on 02/03/1937
(2) 44.60 ft on 04/09/1913
(3) 43.60 ft on 04/04/1975
(4) 43.50 ft on 02/16/1950
(5) 42.94 ft on 03/17/1997

The timing of the floods crests will depend upon a complex mix a factors, including how much rain falls over the next month, the possible influence of southerly winds holding up the floodwater pulses, the potential opening of flood control structures and reduction of flows from flood control reservoirs, and potential levee failures. The Mississippi River is expected to crest at 17 feet at New Orleans on May 22, three feet below the top of the levees. This would likely require opening of the Bonnet Carre Spillway 28 miles upstream from New Orleans, to relieve pressure on the city's levees. Opening the spillway drains 250,000 cubic feet per second of flow into Lake Pontchartrain.

Helping out tornado victims
For those who want to lend a helping hand to those impacted by the widespread destruction this month's severe weather has brought, stop by the portlight.org blog.

Related post: Are tornadoes getting stronger and more frequent? The answer is--we don't know.

Jeff Masters

Tornado

Updated: 12:46 PM GMT on May 02, 2011

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Massive tornado outbreak kills 202; 100-year flood coming on Mississippi River

By: JeffMasters, 1:49 PM GMT on April 28, 2011

A stunning tornado outbreak of incredible violence has left at least 202 dead across the Eastern U.S.; injuries probably number over a thousand, with 600 injured in the town of Tuscaloosa alone. The tornadoes carved huge swaths of damage, completely flattening large sections of many towns, and damage from the storms is likely to be the greatest in history for any tornado outbreak. Hardest hit was Alabama, with at least 149 dead; at least 36 were killed in neighboring Mississippi. NOAA's Storm Prediction Center logged 160 preliminary reports of tornadoes between 8am EDT yesterday and 8am EDT today. At least 11 of these tornadoes were killer tornadoes; deaths occurred in six states. Damage from some of these storms appeared to be at least EF-4, and it is likely that there were multiple violent EF-4 or EF-5 tornadoes. The death toll makes the April 27 - 28 outbreak the third deadliest tornado outbreak of the past 50 years, behind the April 3 - 4, 1974 Super Outbreak (315 killed) and the 1965 Palm Sunday tornado outbreak (256 killed.)


Figure 1. Damage in Birmingham, Alabama from last night's tornado. Image posted to twitter.


Figure 2. Damage in Tuscaloosa, Alabama from last night's tornado. Image posted to twitter, photographer unknown.


Figure 3. Radar reflectivity image of the Tuscaloosa, Alabama tornado.

The 3-day total of preliminary tornado reports from this outbreak is 278, close to the 323 preliminary tornado reports logged during the massive April 14 - 16 tornado outbreak. That outbreak has 155 confirmed tornadoes so far, making it the largest April tornado outbreak on record. It is unprecedented to have two such massive tornado outbreaks occur so close together. According to a list of tornado outbreaks maintained by Wikipedia, only two other tornado outbreaks have had as many as 150 twisters--the May 2004 outbreak (385), and the May 2003 outbreak (401).


Figure 4. Satellite image of last night's storm at 8:15pm EDT April 27, 2011. Image credit: NASA/GSFC.

Tornado outbreak winding down today
Tornado warnings continue to be issued this morning along the cold front now pushing towards the Atlantic coast, and a tornado was reported at 7:35am EDT in McBee, South Carolina. NOAA's Storm Prediction Center has placed a large swath of the coast, from Florida to Vermont, in their "Slight Risk" region for severe weather. The high instability and high wind shear that triggered so many killer tornadoes yesterday is gone, and we should see only a few weak tornadoes today. No severe storms are predicted for Friday. Saturday has a slight risk of severe weather over Oklahoma and Texas.


Figure 5. Severe weather threat for Thursday, April 28, 2011.


Figure 6. Remarkable video of the tornado that hit Tuscaloosa, Alabama yesterday. Fast forward to minute four to see the worst of the storm.


Figure 8. Tornado near Empire, Alabama, moving rapidly down a hill.

Unprecedented flooding predicted on Ohio and Mississippi Rivers
This week's storm system, in combination with heavy rains earlier this month, have pushed the Ohio River and Mississippi River to near-record levels near their confluence. The Ohio River at Cairo, Illinois is expected to crest at 60.5 feet on May 1. This would exceed 100-year flood stage, and be the highest flood in history, besting the 59.5' mark of 1937. Heavy rains of 10 - 15 inches have inundated the region over the past few days, and one levee breach at Black River levee near Poplar Bluff, Missouri, has resulted in the evacuation of over 500 homes. Poplar Bluff has received 15.45" of rain since Friday morning. The greatest rain gauge-measured precipitation from the storm occurred in Springdale, Arkansas, where 19.70" inches has fallen since Friday morning.


Figure 9. The latest River Flood Outlook from NOAA shows major flooding is occurring over many of the nation's major rivers.

Record 100+ year flood expected on Mississippi River
Snow melt from this winter's record snow pack across the Upper Mississippi River has formed a pulse of flood waters that is moving downstream on the Mississippi, and is currently located in Iowa. When this floodwater pulse moves south of Cairo, Illinois over the next two weeks, it will join with the record water flow coming out of the Ohio River, and create the highest flood heights ever recorded on the Mississippi, according to the latest forecasts from the National Weather Service. Along a 400-mile stretch of the Mississippi, from Cairo to Natchez, Mississippi the Mississippi is expected to experience the highest flood heights since records began 100 or more years ago, at 5 of the 10 gauges on the river along this stretch. The records are predicted to begin to fall on May 3 at New Madrid, and progress downstream to Natchez by May 20. Areas that are not protected by levees can expect extensive damage from the flooding, and it is possible that the Army Corps of Engineers will have to intentionally dynamite a levee at Birds Point and New Madrid, Missouri to protect the town of Cairo from flooding.

The Mississippi River at New Madrid, MO, about 40 miles downstream of the confluence of the Mississippi and Ohio Rivers, is currently at 44', the 3rd highest flood in history. The river is predicted to crest on Tuesday very near the all-time record height of 48 feet. The NWS warns that at this height, "Large amounts of property damage can be expected. Evacuation of many homes and businesses becomes necessary." Previous record heights at this location:

(1) 48.00 ft on 02/03/1937
(2) 44.60 ft on 04/09/1913
(3) 43.60 ft on 04/04/1975
(4) 43.50 ft on 02/16/1950
(5) 42.94 ft on 03/17/1997

The timing of the floods crests will depend upon a complex mix a factors, including how much rain falls over the next month, the possible influence of southerly winds holding up the floodwater pulses, the potential opening of flood control structures and reduction of flows from flood control reservoirs, and potential levee failures (no levee has failed on the Lower Mississippi south of the Ohio River junction since 1950, however.) The Mississippi River is expected to crest at 17 feet at New Orleans on May 22, three feet below the top of the levees. This would likely require opening of the Bonnet Carre Spillway 28 miles upstream from New Orleans, to relieve pressure on the city's levees. Opening the spillway drains 250,000 cubic feet per second of flow into Lake Pontchartrain.

Helping out tornado victims
For those who want to lend a helping hand to those impacted by the widespread destruction this month's severe weather has brought, stop by the portlight.org blog.

Related post: Are tornadoes getting stronger and more frequent? The answer is--we don't know.

Jeff Masters

Flood Tornado

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Tornadoes, floods, and fires continue to pound U.S.

By: JeffMasters, 3:13 PM GMT on April 27, 2011

The nation's unprecedented April tornado-fest continued full force last night, with NOAA's Storm Prediction Center logging 57 tornado reports, 295 cases of damaging thunderstorm winds, and 254 reports of large hail. The 2-day tornado count from this latest huge April tornado outbreak is already 102. With another "high risk" forecast for tornadoes today, the tornado total for this week's outbreak may rival the April 14 - 16 tornado outbreak (155 confirmed tornadoes) as the greatest April tornado outbreak in history. It is unprecedented to have two such massive tornado outbreaks occur so close together, and the April preliminary tornado count of 654 is truly stunning. Even adjusting this number downwards 15% (the typical over-count in preliminary tornado reports) yields a probable April tornado total of 550. This easily crushes the previous April tornado record of 267, set in 1974. An average April has "only" 163 tornadoes, so we are already 300% over average for the month, and may approach 400% after today's outbreak. According to a list of tornado outbreaks maintained by Wikipedia, only two other tornado outbreaks have had as many as 150 twisters--the May 2004 outbreak (385), and the May 2003 outbreak (401). One positive note--there has only been one violent EF-4 or stronger tornado this year, despite the fact we've already had about 2/3 of the 1200 tornadoes one typically gets for the entire year. Over the past 20 years, we've averaged 7 violent EF-4 or EF-5 tornadoes per year, so we should have had 4 or 5 of these most dangerous of tornadoes so far this year.


Figure 1. Satellite image of last night's storm at 8pm EDT April 26, 2011. Image credit: NASA/GSFC.

Fortunately, no one was killed in last night's tornado frenzy, but four twisters caused injuries, with 7 injuries in Hesterman, Mississippi, and 3 in Beekman, Louisiana. Over 100 homes were damaged when a tornado struck Edom, Texas, approximately 75 miles East of Dallas. One woman was injured when her mobile home was destroyed. The only killer tornado of the current outbreak occurred on Monday night at 7:30 pm CDT when a 1/2 mile-wide EF-2 tornado struck the small town of Vilonia, Arkansas. Four people died in the town, where 50 - 80 buildings were destroyed. Tornado warnings were issued 30 minutes before the storm hit, contributing to the relatively low loss of life.


Figure 2. Storm chaser video of a tornado yesterday in Ben Wheeler, Texas.

Another very dangerous tornado outbreak expected today
The busiest April in history for tornadoes continues full-force today, as NOAA's Storm Prediction Center has issued their highest level of severe weather potential, a "High Risk" forecast, for Northern Alabama, Southern Tennessee, and adjoining portions of Georgia and Mississippi. This is the second day in a row, and third time this year, that SPC has issued a "High Risk" forecast. The devastating North Carolina tornado outbreak of April 16, which generated 52 confirmed tornadoes that killed 24 people in North Carolina and 2 people in Virginia, was the other "high risk" day. Numerous tornado warnings have already been issued in Tennessee, Kentucky, Georgia, Mississippi, Arkansas, Ohio, and Alabama this morning, but today's main action is expected to erupt late this afternoon as the cold front from a low pressure system currently over Arkansas moves eastwards over the "high risk" area. Strong daytime heating in a very moist, unstable airmass will allow a tremendous amount of energy to build up ahead of the front. The arrival of the cold front will force the warm, moist air upwards, allowing the pent-up energy to burst out and fuel supercell thunderstorms.

Related post: Are tornadoes getting stronger and more frequent?


Figure 3. Severe weather threat for Wednesday, April 27, 2011.

Unprecedented flooding predicted on Ohio River
This week's storm system, in combination with heavy rains earlier this month, have pushed the Ohio River and Mississippi River to near-record levels near their confluence. The Ohio River at Cairo, Illinois is expected to crest at 60.5 feet on May 1. This would exceed 100-year flood stage, and be the highest flood in history, besting the 59.5' mark of 1937. Heavy rains of 10 - 15 inches have inundated the region over the past few days, and one levee breach at Black River levee near Poplar Bluff, Missouri, has resulted in the evacuation of over 500 homes. Poplar Bluff has received 15.45" of rain since Friday morning. The greatest rain gauge-measured precipitation from the storm occurred in Springdale, Arkansas, where 19.70" inches has fallen since Friday morning.


Figure 4. The latest River Flood Outlook from NOAA shows major flooding is occurring over many of the nation's major rivers.

Extraordinary intentional levee breach of Mississippi River halted by lawsuit
In a sign of just how extreme this flooding situation is, yesterday the Army Corps of Engineers, which is responsible for flood control efforts on the Mississippi River, announced plans to intentionally destroy a levee protecting the west bank of the Mississippi River in Southwest Missouri. The destruction of the levee is intended to relieve pressure on the levees at Cairo, Illinois, at the confluence of the Mississippi and Ohio Rivers. Cairo is currently under a voluntary evacuation order. The levee to be destroyed, located at Birds Point, is called a "fuse-plug" levee, and was designed to be destroyed in the event of a record flood. The levee protects 132,000 acres of prime farmland along the New Madrid Spillway, which is designed to take 550,000 cubic feet per second of water flow out of the Mississippi and redirect it down a 3 - 10 mile wide, 36 - 56 mile long path along the west side of the Mississippi. An 11-mile long section of the levee upstream at Birds Point, and 5-mile long stretch at the downstream end, are set two feet lower than the surrounding levees and filled with holes to accommodate dynamite. These levees will be destroyed if the Army Corps has its way, but a lawsuit by the state of Missouri is currently blocking the way. The Army Corps has now agreed to wait until Saturday to decide whether or not to blow the levee. The Army Corps' website has an unofficial damage estimate of $100 million for destroying the levees and flooding the New Madrid Spillway. At least 100 people live in the spillway and have been evacuated, and it would likely take many years for the farms to recover after flooding. The levees have been blown and the spillway opened only once before, back during the record flood of 1937.

Midwest deluge enhanced by near-record Gulf of Mexico sea surface temperatures
The deluge of rain that caused this flood found its genesis in a flow of warm, humid air coming from the Gulf of Mexico. Sea surface temperatures (SSTs )in the Gulf of Mexico are currently close to 1 °C above average. Only two Aprils since the 1800s (2002 and 1991) have had April SSTs more than 1 °C above average, so current SSTs are among the highest on record. These warm ocean temperatures helped set record high air temperatures in many locations in Texas yesterday, including Galveston (84°F, a tie with 1898), Del Rio (104°F, old record 103° in 1984), San Angelo (97°F, old record 96° in 1994). Record highs were also set on Monday in Baton Rouge and Shreveport in Louisiana, and in Austin, Mineral Wells, and Cotulla la Salle in Texas. Since this week's storm brought plenty of cloud cover that kept temperatures from setting record highs in many locations, a more telling statistic of how warm this air mass was is the huge number of record high minimum temperature records that were set over the past two days. For example, the minimum temperature reached only 79°F in Brownsville, TX Monday morning, beating the previous record high minimum of 77°F set in 2006. In Texas, Austin, Houston, Port Arthur, Cotulla la Salle, Victoria, College Station, Victoria, Corpus Christi, McAllen, and Brownsville all set record high minimums on Monday, as did New Orleans, Lafayette, Monroe, Shreveport, and Alexandria in Louisiana, as well as Jackson and Tupelo in Mississippi. Since record amounts of water vapor can evaporate into air heated to record warm levels, it is not a surprise that incredible rains and unprecedented floods are resulting from this month's near-record warm SSTs in the Gulf of Mexico.


Figure 5. Departure of sea surface temperature from average for April 25, 2001. Image credit: NOAA/NESDIS.

Fierce winds fan Texas, New Mexico fires
Fierce winds fanned raging fires across eastern New Mexico and Western Texas yesterday, thanks to a powerful flow of air feeding into the Midwestern storm system. Temperatures in the upper 80s and low 90s combined with humidities less than 10% combined to make yesterday a nightmare fire day for firefighters attempting to control the worst springtime fires in the history of the region. At 3:53 pm MDT yesterday in Carlsbad, New Mexico, the temperature was 87°F, winds were 38 mph gusting to 46, and the humidity was 8%--a perfect storm for extreme fire weather. In Fort Stockton, Texas near the huge Rock House fire, the temperature was 91°F, winds were 35 mph gusting to 44, visibility was reduced to 5 miles due to haze and smoke, and the humidity was 5% at 5:53pm CDT. According to the Interagency Fire Center, wildfires in 2011 have already burned nearly 2.3 million acres in the U.S. This is the greatest acreage on record so early in the year, and is more area than burned all of last year. The largest U.S. acreage to burn since 1960 was the 9.9 million acres that burned in 2007, so we area already 25% of the way to the all-time record fire year--with summer still more than a month away. The fire weather forecast for today is better then yesterday, with winds not expected to blow nearly as strong.


Figure 6. Major wildfires and smoke plumes as visualized using our wundermap with the "fire" layer turned on.

For those who want to lend a helping hand to those impacted by the widespread destruction this month's severe weather has brought, stop by the portlight.org blog.

Jeff Masters

Flood Tornado

Updated: 5:01 PM GMT on April 27, 2011

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Tornadoes, floods, and fires assault the nation

By: JeffMasters, 2:43 PM GMT on April 26, 2011

A 1/2 mile-wide tornado smashed through Vilonia, Arkansas last night, killing four and destroying 50 - 80 houses. Vilonia is a small town of 3,800 north of Little Rock. The storm system responsible produced 38 suspected tornadoes yesterday, and also dumped 10 - 15 inches of rain over portions of Arkansas and southern Missouri. Flash flooding from the heavy rains killed four people in Arkansas last night. The heavy rains have also resulted in overtopping of the Black River levee near Poplar Bluff, Missouri, and over 500 homes have been evacuated in the town due to fears that the levee might fail. Poplar Bluff has received 12.86" of rain over the past three days, as of 11am EDT this morning. The greatest rain gauge-measured precipitation from the storm occurred in Springdale, Arkansas, where 17.09" inches has fallen.


Figure 1. Animation of a supercell thunderstorm 45 minutes after it produced the Viloni, Arkansas tornado at 7:25 pm CDT.


Figure 2. Radar-estimated precipitation from last night's storms.

Dangerous tornado outbreak expected today
Yesterday's tornado outbreak was merely a warm-up for today's onslaught, as NOAA's Storm Prediction Center has issued their highest level of severe weather potential, a "High Risk" forecast, for Northeast Texas and Southern Arkansas. This is just the second time this year that SPC has issued a "High Risk" forecast--the other was for the devastating North Carolina tornado outbreak of April 16, which generated 52 tornadoes that killed 26 people. Severe thunderstorms have already rumbled across Louisiana and Mississippi this morning, but today's main action is expected to erupt late this afternoon and early this evening in the "high risk" area. The tornado and severe weather outbreak will continue on Wednesday, when severe weather is expected to be concentrated in Tennessee and Kentucky, with a "moderate risk" of tornadoes. Preliminary tornado reports for the year 2011 show that this year is probably the busiest tornado season on record for this point in the season.


Figure 3. Severe weather threat for Tuesday, April 26, 2011.


Figure 4.
Chaser video of the Viloni, Arkansas tornado of April 25, 2011.

Extremely critical fire danger in Texas and New Mexico today
Spring storms commonly bring high winds to the Midwest this time of year, but today's storm will bring exceptionally high winds--and no precipitation--to the drought-stricken regions of West Texas and eastern New Mexico. As a result, an "extremely critical" fire weather day has been declared by the National Weather Service for the region, where high temperatures, low humidities, and powerful winds gusting to 60 mph will occur. The 24,000 acre Last Chance fire burning 33 miles southwest of Carlsbad, New Mexico near the Texas border is a particular concern, since it is currently 0% contained and is threatening many structures. This fire is expected to rage out of control today, thanks to humidities near 5%, temperatures in the low 90s, sustained winds near 40 mph, and gusts to 60 mph.


Figure 5. Fire weather forecast for today from NOAA's Storm Prediction Center.

2011 sets record for most acreage burned for April
According to the Interagency Fire Center, wildfires in 2011 have already burned nearly 2.3 million acres in the U.S. This is the greatest acreage on record so early in the year, and is more area than burned all of last year. The largest U.S. acreage to burn since 1960 was the 9.9 million acres that burned in 2007, so we area already 25% of the way to the all-time record fire year--with summer still more than a month away. Last night, a line of thunderstorms brought heavy rains of 2 - 3 inches from Dallas southeastwards through Louisiana, providing precious rains to a portion of Texas that was under their worst drought since 1925. However, the portion of Texas that has seen the worst wildfires (the black spots in the image below), received no rain.


Figure 6. Perimeters of the major wildfires in Texas during 2011 as of April 25. Image credit: GEOMAC Wildland Fire Support.

For those who want to lend a helping hand to those impacted by the widespread destruction this month's severe weather has brought, stop by the portlight.org blog.

Jeff Masters

Flood Tornado

Updated: 6:04 PM GMT on April 26, 2011

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March is the 13th warmest on record; major tornado outbreak expected

By: JeffMasters, 12:30 PM GMT on April 25, 2011

March 2011 was the globe's 13th warmest March on record, according to the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC). NASA's Goddard Institute for Space Studies rated March the 9th warmest on record. March 2011 global ocean temperatures were the 12th warmest on record, and land temperatures were the 12th warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were below average, the 12th or 15th coolest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). The global cool-down from November, which was the warmest November on record for the globe, was due in large part to a La Niña episode in the Eastern Pacific. The large amount of cold water that upwells to the surface during a La Niña typically causes a substantial cool-down in global temperatures. The coldest place on the globe in March, relative to average, was Central and Western Canada. The Asian portion of Russia was exceptionally warm, relative to average.

Our weather historian, Christopher C. Burt, has a nice summary of some of the remarkable weather extremes of March 2011.


Figure 1. Departure of temperature from average for March 2011. Image credit: National Climatic Data Center (NCDC).

Congo sets its all-time heat record
The Democratic Republic of the Congo, the world's 12th largest country, set a new all-time extreme heat record on March 8, 2011, when the temperature hit 39.2°C (102.6°F) at M'Pouya. Congo's previous all-time hottest temperature was 39.0°C (102.2°F) at Impfondo on May 14, 2005. Congo is the first nation to set an all-time extreme heat or cold record in 2011. Last year, a record 19 nations, plus the UK's Ascension Island territory, set all-time extreme heat records. I thank weather records researchers Maximiliano Herrera, Christoper C. Burt, and Howard Rainford for their assistance researching these records.

A moderately warm and wet March for the U.S.
For the contiguous U.S., March temperatures were warmer than average, ranking the 39th warmest in the 117-year record, according to the National Climatic Data Center. Only New Mexico had a top ten warmest March; no states had a top ten coldest March. Precipitation was above average, with the month ranking as the 34th wettest March since 1895. Texas had its driest March on record, and top ten driest Marches were experienced in New Mexico and Oklahoma. Washington, Oregon, California, and Pennsylvania had top ten wettest Marches.

La Niña remains weak
La Niña conditions remain weak over the Eastern Pacific, with sea surface temperatures (SSTs) in the equatorial Eastern Pacific about 0.6°C below average. An animation of SSTs since late December shows the weakening La Niña nicely. Springtime is the most common time for a La Niña event to end; since 1950, half of all La Niñas ended in March, April, or May. The weakness displayed by the current La Niña event has prompted NOAA's Climate Prediction Center to predict that La Niña will be gone by June.

Sea ice extent in the Arctic 2nd lowest on record during March
March 2011 Northern Hemisphere sea ice extent was second lowest on record, according to the National Snow and Ice Data Center. Satellite records extend back to 1979. This breaks a string of three consecutive months of record low Arctic sea ice cover.

Major tornado outbreak expected today through Wednesday
Another huge tornado outbreak is likely this week over the U.S., as a strong storm system that is developing over the Mississippi Valley today moves slowly eastwards during the week. A 3-day tornado total of over 100 twisters is quite possible today through Wednesday. NOAA's Storm Prediction Center has issued its "moderate risk" forecast for severe weather today, centered over Arkansas. This region has a significant risk of tornadoes, some of them strong EF-2 and EF-3 strength. A more serious threat of severe weather exists for Tuesday over Arkansas and surrounding states, with the Storm Prediction Center calling the situation "potentially significant/dangerous." The heightened severe weather risk extends through Wednesday, with a moderate risk of tornadoes and severe weather in Tennessee and surrounding states. Preliminary tornado reports for the year 2011 show that this year is probably already the busiest tornado season on record for this point in the season. This week's action will substantially pad the record.


Figure 2. Severe weather threat for Monday, April 25, 2011.

St. Louis tornado rated an EF-4
A violent EF-4 tornado ripped through St. Louis near 8pm local time Friday night, carving a 22-mile path of destruction up to 0.4 miles wide, and severely damaging Lambert International Airport. The airport, the world's 30th busiest, was closed much of the weekend, but has now re-opened. The tornado, rated an EF-2 when it hit the airport, ripped off the roof from Concourse C, blew out more than half of the windows in the main terminal, and moved an aircraft that was parked at a gate twenty feet. The tornado also passed over a residential area just west of the airport in the community of Bridgton, causing severe EF-4 damage, according to the National Weather Service office in St. Louis. This was the first violent EF-4 tornado of the year.


Figure 3.
Remarkable video from a security camera at the St. Louis airport showing the roof being torn off Concourse C.


Figure 4.Before and after damage photo of Beaverton Drive in Bridgeton, Missouri, after the April 22, 2011 tornado. This damage was rated EF3. Image credit: National Weather Service office in St. Louis and Google.

Jeff Masters

Climate Summaries

Updated: 12:30 PM GMT on April 25, 2011

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Violent EF-4 tornado causes severe damage at St. Louis' airport

By: JeffMasters, 3:25 PM GMT on April 23, 2011

A violent EF-4 tornado ripped through St. Louis near 8pm local time Friday night, severely damaging Lambert International Airport. The airport, the world's 30th busiest, may be closed for several days. The tornado ripped off the roof from Concourse C, blew out more than half of the windows in the main terminal, and moved an aircraft that was parked at a gate twenty feet. So far, only minor injuries due to flying glass have been reported from the tornado. The tornado also passed over nearby residential areas, causing severe damage. The National Weather Service office in St. Louis has rated the damage from the St. Louis tornado EF-4, making the twister the first violent EF-4 tornado of the year. Softball-sized hail also pelted three towns in Missouri--Hermann, Big Spring, and Warrenton--during Friday night's severe weather outbreak. NOAA's Storm Prediction Center logged 24 tornado reports Friday in Oklahoma, Arkansas, Missouri, Illinois, and Kentucky. The cold front responsible for triggering last night's severe weather will remain draped over the nation's mid-section for the next three days, and a slight risk of severe weather is predicted along a swath from Texas to Ohio both Saturday and Sunday. A more substantial risk of severe weather is likely on Tuesday through Wednesday, as a new, more powerful spring storm system gathers strength over the Midwest.


Figure 1. Radar reflectivity image of the EF-4 St. Louis tornado taken near 8pm local time on Friday, April 22, 2010. This image is from the high-resolution Terminal Doppler Radar (TDR) at the St. Louis Airport, and shows very fine details of the tornado, which displays a classic hook echo here.


Figure 2. Radar Doppler velocity image of the St. Louis tornado taken near 8pm local time on Friday, April 22, 2010. This image is from the high-resolution Terminal Doppler Radar (TDR) at the St. Louis Airport, located at the "+" sign on the image. Green colors denote areas where precipitation is moving towards the radar, and red and yellow colors show where precipitation is moving away from the radar. Pink colors are bad data regions. The small couplet of greens right next to reds is where the tornado was, since the tight vortex had winds moving towards the radar and away from the radar. The area marked "RFD" shows where a Rear-Flank Downdraft (RFD) was occurring behind the tornado. The downdraft hit the ground to the west of the radar site and spread out in all directions, creating a diverging area of winds moving both towards and away from the radar. An area of air flowing into the tornado on the SE side is marked "Inflow." Thanks go to Dr. Rob Carver, wunderground's tornado expert, for annotating this image.


Figure 3.
Remarkable video from a security camera at the St. Louis airport showing the roof being torn off Concourse C.


Figure 4. Severe damage characteristic of at least a strong EF-2 tornado is apparent from this helicopter view of residential St. Louis neighborhoods taken by KMOV.

Jeff Masters

Tornado

Updated: 2:52 PM GMT on April 26, 2011

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Invest 91L more organized, but has little time to develop

By: JeffMasters, 2:31 PM GMT on April 22, 2011

Hurricane season is more than a month away, but we have a tropical disturbance (91L) typical of what one might see in June or November. 91L is spinning over the waters a few hundred miles south of Bermuda, and has improved considerably in organization since yesterday, thanks to a drop in wind shear. The latest SHIPS model output is showing shear of 40 - 55 knots over 91L, but shear analyses from the University of Wisconsin CIMSS group is showing lower shear values of 20 - 30 knots over the main circulation center and to 91L's north, where the heaviest thunderstorms are. The system has a warm core at low levels, but a trough of low pressure lies over the storm at upper levels, and this trough is pumping cold, dry air into 91L, making it not completely tropical. One characteristic of subtropical systems like 91L is the presence of the main band of heavy thunderstorms removed several hundred miles from the circulation center, and 91L fits that description. 91L has two centers of circulation competing to be dominant, and this competition is slowing the storm's development. The storm was headed north at 5 - 10 mph early this morning, but that motion has halted, and 91L appears to be moving more south-southwesterly now, away from Bermuda. Sea surface temperatures are 23°C, which are very cold for a tropical storm to form in, but could support development of a subtropical storm.

As 91L moves south today, shear will steadily rise, and the storm likely has only until Friday night before shear grows too high to permit development. NHC is giving 91L a 20% chance of developing into a subtropical or tropical depression, which is a reasonable forecast. There has been only been one named April storm in the Atlantic since 1851, Tropical Storm Ana of 2003. The formation of a tropical disturbance at this location this time of year is unusual, but is not a harbinger of a active season ahead. Had this been going on in the Caribbean, that would be a different story.


Figure 1. Morning satellite image of the Atlantic tropical disturbance 91L. Note the two centers of circulation competing to be dominant. I expect the northern center will become dominant.

Jeff Masters

Hurricane

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Atlantic tropical disturbance 91L poses little threat

By: JeffMasters, 2:15 PM GMT on April 21, 2011

A tropical disturbance (91L) near 24N, 63W, midway between the Virgin Islands and Bermuda, is moving north-northwest at about 8 mph. The system's heavy thunderstorm activity has increased since yesterday, but 91L has an elongated and poorly-organized circulation, thanks to a hefty 80 knots of wind shear. The storm is over waters of 25°C, and these waters will cool to 24°C by Friday as the storm continues to the north-northwest. Before 91L reaches Bermuda, steering currents will reverse and force 91L to the south-southwest on Saturday, into a region of higher wind shear. The latest SHIPS model forecast predicts wind shear will drop to 50 knots over 91L by Friday, then increase again to 70 knots by Sunday. The high shear and relatively cool water temperatures will make it difficult for 91L to organize into a subtropical depression. I give 91L a 10% of becoming a subtropical depression. Climatology argues against 91L becoming the first named storm of the year; there has only been once named April storm in the Atlantic since 1851, Tropical Storm Ana of 2003. The formation of a tropical disturbance at this location this time of year is unusual, but is not necessarily a harbinger of a active season ahead.


Figure 1. Morning satellite image of the Atlantic tropical disturbance 91L.

Jeff Masters

Hurricane

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Tornadoes, huge hail pound the Midwest, but bring little Texas drought relief

By: JeffMasters, 12:41 PM GMT on April 20, 2011

Severe weather blasted the Midwest again yesterday, with NOAA's Storm Prediction Center logging 32 reports of tornadoes, 399 reports of damaging thunderstorm winds, and 325 instances of large hail (including softball-sized hail of 4.25 - 4.5" diameter in Clarkesville, MO and Stringtown, OK.) Fortunately, no deaths or injuries were reported from yesterday's storms. The storm also brought the heaviest snow so late in the season to Green Bay, Wisconsin--9.9 inches. This brought the seasonal total for Green Bay to 92.4", the third most on record.

The storm responsible will trek eastwards today, bringing the threat of severe weather to regions of the Southeast hard-hit by last week's remarkable tornado outbreak. NOAA's Storm Prediction Center has placed a wide swath of the country from Eastern Texas to New Jersey under their "slight risk" for severe weather. According to the latest tornado tallies on the excellent Wikipedia page on the April 14 - 16 tornado outbreak, 128 tornadoes are confirmed to have occurred, with 39 of these strong EF-2 and EF-3 twisters. Remarkably, there have been no violent EF-4 or EF-5 tornadoes reported yet in 2011, despite the fact that the preliminary 2011 tornado count as compiled by SPC is 611, which will likely make 2011 the most active tornado season on record for this point in the year.


Figure 1. Satellite image taken at 8pm EDT on Tuesday, April 19, 2011, of the storm system that brought severe weather to the Midwest. Image credit: NASA/GSFC.


Figure 2. Severe weather outlook for today.

Yesterday's storms bring little drought relief for Texas
Yesterday's severe weather outbreak brought a few thunderstorms to the Dallas/Fort Worth area last night, with up to two inches of welcome rain falling in isolated areas. However, the rains missed the areas of Texas where the worst fires area burning, and strong winds associated with the spring storm helped whip up the fires. Winds will not be as strong today, and the latest 1 - 5 day rainfall forecasts show the possibility of isolated thunderstorms bringing drought relief to the same portions of Texas that benefited from last night's rains. These rains will not be enough to significantly slow down the record fires scorching Texas, though, and the latest 2-week forecast from the GFS model shows little chance of drought-busting rains over Texas into early May.


Figure 2. Total rainfall for North Texas from last night's storms brought only isolated drought relief.

Atlantic tropical disturbance
As a reminder that hurricane season is not that far away, an area of disturbed weather has formed in the Atlantic near 23N, 80W, about 700 miles northeast of Puerto Rico. This system is under a hefty 60 knots of wind shear, but does have a surface circulation. The disturbance's heavy thunderstorm activity has been removed well to the northeast of the surface circulation center by the high wind shear. The storm is expected to move northwest into a region of lower wind shear on Thursday and Friday, and should begin building more heavy thunderstorms during the next three days. The storm is not a threat to any land areas, and will likely be ripped apart by high wind shear this weekend. It has perhaps a 10% chance of becoming a subtropical depression before then. Climatology argues against this storm becoming the first named storm of the year; there has only been once named April storm in the Atlantic since 1851, Tropical Storm Ana of 2003.


Figure 4. Morning satellite image of the Atlantic tropical disturbance 700 miles northeast of Puerto Rico.

Jeff Masters

Tornado

Updated: 12:46 PM GMT on April 20, 2011

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Historic 3-day tornado outbreak kills at least 40

By: JeffMasters, 2:45 PM GMT on April 18, 2011

In a stunning display of violence, close to 200 tornadoes rampaged across the Midwestern and Southeast U.S. April 14 - 16 in one of the largest tornado outbreaks in history. At least 40 people died in the tornadoes, making it the deadliest tornado outbreak since the Super Tuesday tornado outbreak of February 5 - 6, 2008, which killed 57 people. Severe thunderstorms and flash floods killed at least seven more people in this April's severe weather outbreak. Hardest hit was Bertie Country in northeast North Carolina, where an EF-3 tornado carved a path of destruction 18.8 miles long and 1/2 - 3/4 miles wide, killing 11 people in the town of Colerain. It was the deadliest single tornado in the United States since May 10, 2008 in Picher, Oklahoma and Neosho, Missouri, which killed 21. Also hard-hit Saturday was the Raleigh area, where a 3/10 mile-wide tornado carved a 63-mile long path of destruction through downtown. Damage was rated EF-2 in downtown Raleigh, but was EF-3 along other portions of its path, and the tornado killed five people. The 23 tornado deaths in North Carolina made Saturday's outbreak the deadliest day for tornadoes in the state since 1984, when the infamous March 28 tornado outbreak killed 57 people and injured 1248. The 1984 outbreak had more violent tornadoes--seven F4 twisters in all. None of the tornadoes in this year's outbreak have been rated above EF-3, as of yet.


Figure 1. Viewer-uploaded photo sent to WRAL of damage in Fayetteville, NC on Saturday.


Figure 2. Radar reflectivity image of North Carolina on Saturday during the height of the tornado outbreak, showing four simultaneous hook echoes of tornadoes. The storm at the top of the image is the EF-3 tornado that ripped through Raleigh, killing five people.

One of the largest tornado outbreaks in history
NOAA's Storm Prediction Center logged 120 preliminary tornado reports on Saturday, 120 on Friday, and 27 on Thursday, bringing the 3-day total to 267 twisters. In past years, these preliminary tornado reports typically were an over-count of the actual confirmed tornado totals by about 15%. However, this year the Storm Prediction Center stopped trying to filter out preliminary reports they thought were from the same tornado, so the over-count may be higher. Even so, the 3-day April 14 - 16 2011 tornado outbreak will likely will end up with close to 200 confirmed tornadoes, making it the largest tornado outbreak since the 235 tornadoes recorded in the May 22 - 31, 2008 outbreak. According to a list of tornado outbreaks maintained by Wikipedia, only two other tornado outbreaks have had as many as 150 twisters--the May 2004 outbreak (385), and the May 2003 outbreak (401). An average April typically has 150 - 160 tornadoes across the entire U.S.


Figure 3. North Carolina Department of Transportation worker Steven Hoag sat in his car filming the EF-2 tornado that hit Wilson, North Carolina on Saturday. We can hear his side of a cell phone conversation to his sister as the tornado passes directly over him, unroofing a Walgreens store across the street. His calmness and lack of concern are truly extraordinary to hear (in an interview with the local ABC affiliate, Hoag attributes his calmness to his family upbringing, and to being an ex-Marine.) Hoag was very fortunate, as the 120-mph winds of the tornado rolled several cars as much as 100 feet.

Another significant severe weather outbreak coming on Tuesday
NOAA's Storm Prediction Center is predicting another major severe weather outbreak for the Midwest on Tuesday, when a strong cold front is expected to sweep across the Mississippi and Ohio River Valleys. A "moderate" risk of severe weather is expected across much of Missouri, Illinois, and Indiana. The weather conditions are not expected to be as conducive for severe weather as was the case Saturday, when SPC placed much of North Carolina in their "high risk" area for severe weather, the only "high risk" forecast they've issued this year.


Figure 4. Severe weather risk for Tuesday.

Wikipedia has a nice summary of the April 14 - 16 tornado outbreak.

Jeff Masters

Tornado

Updated: 2:52 PM GMT on April 19, 2011

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Tornadoes pound North Carolina and Virginia, killing 25

By: JeffMasters, 3:45 PM GMT on April 17, 2011

In a stunning display of violence, dozens of tornadoes rampaged through North Carolina and Virginia on Saturday, killing at least 25 people, injuring at least 130, and damaging or destroying at least 450 homes and businesses. Hardest hit in yesterday's outbreak was the the town of Askewville in northeast North Carolina, where a violent tornado that was likely at least an EF-3 ripped homes off their foundations and killed eleven people. Also hard-hit was the Raleigh area, where a mile-wide EF-3 tornado with 140 - 150 mph winds roared through the downtown region, killing five people. The 22 deaths in North Carolina made yesterday's outbreak the deadliest day for tornadoes in the state since 1984, when the infamous March 28 tornado outbreak killed 57 people and injured 1248.


Figure 1. Viewer-uploaded photo sent to WRAL of the Raleigh tornado shortly before it leveled a Lowes store in Sanford, NC.


Figure 2. Radar reflectivity loop of the Raleigh, North Carolina tornado at 3:59pm EDT as the twister passed through downtown. Note the classic hook-shaped echo of the parent mesocyclone in the rotating severe thunderstorms that spawned the tornado.


Figure 3. Doppler radar velocity image of the Raleigh, North Carolina tornado at 3:59pm EDT.

NOAA's Storm Prediction Center logged 105 tornado reports on Saturday, 113 on Friday, and 23 on Thursday, bringing the 3-day total to 241 twisters. These preliminary tornado reports are typically an over-count of about 15%, so the 3-day April 14 - 16 2011 tornado outbreak likely will end up with 200 - 210 confirmed tornadoes. This is a huge number of tornadoes; an average April typically has just 150 tornadoes across the entire U.S.

On Thursday, the first day of this remarkable outbreak, 23 tornadoes and numerous deadly severe thunderstorms tore through Oklahoma and Arkansas, killing at least nine people. An EF-3 tornado hit the small town of Tushka, Oklahoma, population 350, ripping off the roof of the local high school and destroying dozens of buildings in Tushka. Two people were killed and 25 injured. The tornado moved over farmland and dissipated a short time later, but the squall line that spawned the tornado moved into Arkansas Thursday night, spawning severe thunderstorm winds that killed seven more people. The outbreak ramped up significantly on Friday, with 113 tornado reports. The deadliest tornado of the day an EF-3 twister that hit Prattville, Alabama at 10:55pm CDT, killing three people in a mobile home, and injuring four others. One of the most damaging tornadoes occurred just west of Jackson, Mississippi, when an EF-3 tornado touched down just south of I-20, crossed the expressway, flipping cars and semis, then plowed through the town of Clinton. At least nine people were injured in Clinton, and Malaco Records, one of the top Blues/Gospel/Soul labels in the country, was destroyed by the tornado.


Figure 4. Satellite image from 21:40 UTC (5:40pm EDT) April 16, 2011, showing the strong low pressure system that brought yesterday's severe weather outbreak. Image credit: NASA/GSFC.

WRAL has an impressive time lapse animation from a skycam on a tall skyscraper in Raleigh showing what at the time was believed to be a rain-wrapped Raleigh tornado moving through downtown, but was actually just a thunderstorm downdraft.

Wikipedia has a nice summary of the tornado outbreak.

Jeff Masters

Tornado

Updated: 2:00 PM GMT on April 18, 2011

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Tornadoes rip Alabama, Misssissippi; 17 dead in 2-day outbreak

By: JeffMasters, 3:51 PM GMT on April 16, 2011

Dozens of tornadoes and dangerous severe thunderstorms tore through the Southeast U.S. on Friday, bringing a second day of severe weather havoc to the nation. The death toll from the two-day severe blitz now stands at seventeen, with up to 100 people injured and tens of millions of dollars in property damage. NOAA's Storm Prediction Center logged 98 tornado reports yesterday, bringing the two-day total for the outbreak to 120 tornadoes. These preliminary reports are usually a 15% over-count of the actual number of tornadoes, which still means over 100 tornadoes have probably touched down during the past two days. The deadliest tornado of the outbreak hit near Prattville, Alabama at 10:55pm CDT last night, killing three people in a mobile home, and injuring four others. One of the most damaging tornadoes occurred just west of Jackson, Mississippi, when a tornado touched down just south of I-20, crossed the expressway, flipping cars and semis, then plowed through the town of Clinton. At least nine people were injured in Clinton, and extensive damage characteristic of an EF-2 tornado is apparent in damage photos.


Figure 1. Radar reflectivity image of the Clinton, Mississippi tornado at 10:57am CDT as the twister crossed I-20 and hit the town. Note the classic hook-shaped echo of the parent mesocyclone in the rotating severe thunderstorms that spawned the tornado.


Figure 2. Doppler radar velocity image of the Clinton, Mississippi tornado at 10:57am CDT.

On Thursday, tornadoes and deadly severe thunderstorms tore through Oklahoma and Arkansas, killing at least nine people. A EF-3 tornado hit the small town of Tushka, Oklahoma, population 350, ripping off the roof of the local high school and destroying dozens of buildings in Tushka. Two people were killed and 25 injured. The tornado moved over farmland and dissipated a short time later, but the squall line that spawned the tornado moved into Arkansas overnight, spawning severe thunderstorm winds that killed seven more people.

Virginia, North Carolina, and South Carolina under the gun today
The action shifts eastwards to southern Virgina and eastern North Carolina and South Carolina today, which NOAA's Storm Prediction Center have placed under its "moderate risk" region for severe weather. This is the same level of risk as we've seen for the past two days for this storm system, and it is very unusual for this portion of the U.S. to experience such a high severe weather risk. Tornado watches have already been posted for portions of Georgia, South Carolina, and North Carolina. You can follow today's severe weather using our severe weather page and interactive tornado map. This map now shows links to Youtube storm chaser videos of tornadoes, plus any wunderphotos taken of the storm.


Figure 3. Satellite image from 23:32 UTC (7:32pm CDT) April 15, 2011, showing the strong low pressure system over the middle of the country that brought yesterday's severe weather outbreak. Image credit: NASA/GSFC.


Figure 4. Water vapor satellite image from 23:15 UTC (7:15pm CDT) April 15, 2011, showing a dry, eye-like feature in the strong low pressure system over the middle of the country. This eye-like feature persisted for many hours, but was not visible on infrared or visible satellite images. According to an analysis done by Scott Bachmeier at the University of Wisconsin, the stratosphere, which has very dry air, sunk down to the 600 mb height at the center of the storm, and it is possible that dry air from the stratosphere is responsible for this eye-like feature. This is a different mechanism than how hurricanes develop eyes, and yesterday's storm had only a shallow area of low clouds with light rain near the center--nothing like an eyewall of a hurricane. Image credit: NOAA.


Figure 5. Storm chaser video from Reed Timmer of the Clinton, Mississippi tornado on April 15, 2011. Numerous transformers blow as the tornado wipes out power lines, creating bright blue-green flashes.


Figure 6. Storm chaser video from tornadovideos.net of a huge tornado in Oklahoma during Thursday's outbreak there.

Jeff Masters

Tornado

Updated: 3:54 PM GMT on April 16, 2011

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Tornadoes, severe thunderstorms kill nine in OK, AR; more severe weather today

By: JeffMasters, 1:07 PM GMT on April 15, 2011

Tornadoes and deadly severe thunderstorms tore through Oklahoma and Arkansas last night, killing at least nine people. The action began Thursday afternoon, when a powerful spring low pressure system intensified over western Kansas. The intensifying storm pulled in frigid Canadian air behind it and warm, moist Gulf of Mexico air in front of it, and where two air masses collided over eastern Oklahoma, a powerful cold front spawned a dangerous squall line of severe thunderstorms late Thursday afternoon. Doppler radar indicated the spinning signatures of mesocyclones inside numerous thunderstorms, and the National Weather Service began issuing multiple tornado warnings. At 6:22pm CDT, storm spotters reported a wide "stovepipe" shaped tornado had touched down in south-central Oklahoma four miles south of Milburn in Johnson County. Huge hailstones up to 4 1/2 inches in diameter--the size of softballs--began pelting the ground. The tornado roared to the northeast, ripping through the small town of Tushka, population 350, at 7:23pm. The powerful twister ripped off the roof of the local high school and destroyed dozens of buildings in Tushka, killing two people and injuring 25. The tornado moved over farmland and dissipated a short time later, but the squall line that spawned the tornado moved into Arkansas overnight, spawning severe thunderstorm winds that killed seven more people. The nine deaths made yesterday the deadliest severe weather outbreak of 2011.


Figure 1. Radar reflectivity image of the Tushka, Oklahoma tornado at 7:16pm CDT in Atoka County, seven minutes before the twister hit the town. Note the classic hook-shaped echo of the parent mesocyclone in the rotating severe thunderstorms that spawned the tornado.


Figure 2. Doppler radar velocity image of the Tushka, Oklahoma tornado at 7:16pm CDT in Atoka County, seven minutes before the twister hit the town.

The Tushka tornado brings this year's tornado death tally to five people, which is low for mid-April. In total, yesterday's severe weather outbreak had 10 tornado reports, 122 instances of large hail greater than 2" in diameter, and 91 reports of damaging winds. The action shifts eastwards to Mississippi and Alabama today, which NOAA's Storm Prediction Center have placed under its "moderate risk" region for severe weather. This is the same risk Oklahoma had during yesterday's tornado outbreak. You can follow today's outbreak using our severe weather page and interactive tornado map. This map now shows links to Youtube storm chaser videos of tornadoes, plus any wunderphotos taken of the storm. Tornado warnings have already been posted in Louisiana, Alabama, and Mississippi today. A report visible on our tornado page indicates that a tornado touched down just west of Jackson, Mississippi near noon EDT today, crossing Interstate 20 and ripping the roof off of a bank in Clinton, MS.


Figure 3. Satellite image from 23:03 UTC (5:03pm CDT) April 14, 2011, showing the strong low pressure system over the Plains that brought yesterday's severe weather outbreak. Image credit: NASA/GSFC.


Figure 4. Storm chaser video of the Tushka tornado.

Jeff Masters

Tornado

Updated: 4:39 PM GMT on April 15, 2011

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Huge sandstorm paralyzes Iraq, Kuwait

By: JeffMasters, 8:58 PM GMT on April 13, 2011

A massive sandstorm enveloped Saudi Arabia, Kuwait, and Iraq today, bringing air traffic to a halt and shutting down oil exports from Kuwait. The sandstorm hit Kuwait City between 5am and 6am local time, and by 6:30am, visibility had plunged to 200 meters (656 feet) at Kuwait airport, under a stiff north wind of 20 mph and a temperature of 74°F (23°C). The sandstorm hit Basra, Iraq at the same time, dropping visibility to just 50 meters (164 feet) at the airport.


Figure 1. An intense sandstorm spread dust over northern Saudi Arabia, southern Iraq, Kuwait, and northwards across Iraq to the Caspian Sea in this image taken on the afternoon of April 13, 2011. The nation of Kuwait is entirely covered by dust plumes in this image. Image credit: NASA Earth Observatory.

The dust storm began on April 12, when the cold front trailing from a low pressure system moving across southern Turkey brought very strong westerly winds to Syria, kicking up huge amounts of suffocating dust. At 11am on April 12, winds in Damascus, Syria were 37 mph, gusting to 52 mph as the cold front passed through. As the cold front progressed to the southeast over Syria and Iraq, it kicked up additional dust from the deserts. The cold front and associated dust storm hit Baghdad, Iraq between 6pm and 7pm local time on April 12, with visibility plunging to 50 meters at the airport under northwest winds of 20 mph.

Jeff Masters

Updated: 9:06 PM GMT on April 13, 2011

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Driest March in Texas history fueling huge fires

By: JeffMasters, 2:59 PM GMT on April 12, 2011

Windy, dry and unstable weather conditions are expected for eastern Colorado and New Mexico, eastward to western Kansas, Oklahoma and Texas today--perfect weather for fires. Massive fires continue to rage out of control over large areas of Texas today. Over the past week, the fires scorched hundreds of square miles of rural Texas, destroyed dozens of homes, and sent one fire fighter to the hospital in critical condition. According to the National Interagency Fire Center, 898,000 acres have burned in the U.S. so far this year. This is the 3rd highest burned acreage of the past decade; the record was set in 2006, when a remarkable 2 million acres had burned by April 12.


Figure 1. The Rock House Fire was burning out of control when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite acquired this image on April 10, 2011. Red boxes mark the location of active fires, and brown, charred land shows the fire.s path. A thin plume of smoke streams northeast from the fire front. The burn scar shows that the fire burned around the town of Fort Davis. As of April 12, the National Interagency Fire Center reported that this fire was 80,000 acres and was 0% contained. MODIS also detected a fire immediately northeast of the town of Alpine, in Brewster County, Texas. This fire was 25,000 acres and 0% contained on April 12. Image credit: NASA.


Figure 2. The history of March drought conditions in Texas since 1895, as computed using the Palmer Drought Severity Index (PDSI). The PDSI factors in both precipitation and temperature to come up with a measure of drought severity. Values of the PDSI below -3 are classified as "extreme" drought, and below -4 is the highest classification of drought, "exceptional." This year's drought is the 16th worst March drought in Texas history. Image credit: NOAA/NCDC.

This year's fires caused by heat, drought, and La Niña
When the remains of Hurricane Alex drenched Texas last June, the welcome rains helped fuel a luxurious growth of vegetation across much of Texas during the summer. However, a very cold and dry winter killed off much of that vegetation, leaving plenty of fuel for this spring's fires. With Texas now experiencing the two highest categories of drought, extreme and exceptional, over 60% of its area, conditions are ripe for a record fire season. The percent of the contiguous U.S. covered by extreme and exceptional drought has more than tripled since the beginning of the year, and was near 9% on April 5, according to the U.S. Drought Monitor. An extreme drought is declared when major damage to crops or pasture occurs or widespread water shortages and restrictions. Much of the blame for the drought conditions can be given to the La Niña event occurring the Eastern Pacific. La Niña deflects the jet stream such that the prevailing storm track misses the Southern U.S., leading to dryer and warmer conditions than average during winter and spring. According to the National Climatic Data Center, March 2011 was the driest March and 17th warmest March in Texas since 1895. Temperatures averaged 2 - 6°F above average over most of the state, but over the western portion of the state, where the worst wildfires are burning, temperatures averaged between 6 - 10°F above average. Del Rio has reported only 0.31 inches of precipitation for October - March, the 2nd driest since 1906. Austin reported its 5th driest October - March since 1856, and San Antonio came in as the 12th driest October - March since 1871. Over the last 198 days, from September 26 - April 11, Midland, TX has had measurable precipitation on just five days. Midland's precipitation so far this year stands at just 0.11", compared to a normal of 1.70".


Figure 3. Drought map for April 7, 2011. Image credit: drought.gov.


Figure 4. Winter wheat production for 2010 was heavily concentrated in northern Texas, western Oklahoma, western Kansas, and eastern Colorado, areas strongly impacted by this year's drought. Image credit: U.S. Department of Agriculture.

Drought threatens the winter wheat crop
This spring's drought is heavily impacting the U.S. winter wheat crop, which is concentrated in much of the drought-stricken region (Figure 4.) Winter wheat, which is planted in the fall and harvested in June, accounts for 70% of all wheat plantings in the U.S. The Food and Agriculture Organization (FAO) of the United Nations estimated in March that the 2011 U.S. wheat crop would be 56.6 million tons, 6% less than last year, and the smallest crop since 2007, thanks to the drought. The U.S. wheat crop represents about 8% of the world's total, so a significant reduction of the wheat crop in the U.S. due to a continuation of the spring drought could cause a several percent reduction in the world's wheat supply. Global food prices fell slightly in March, according to the FAO, but still remained among the highest levels since 1990. The drought in the winter wheat areas of the U.S. will create added pressure to this year's high global food prices.


Figure 5. The drought forecast for April, May, and June 2011, issued by NOAA on April 7, calls for drought to spread northwards into all of Kansas and most of Nebraska, and also westwards into most of Arizona and Colorado. Image credit: drought.gov.

A dry forecast
The drought in Texas is likely to get much worse and spread northwards and westwards over the coming months, and will probably rank as one of the top five droughts in Texas history by the time summer arrives. The latest 2-week forecast from the GFS model shows little or no precipitation for the drought region over the next week, with the next chance of significant rains coming April 19 - 20. The latest 1-month and 3-month outlooks from the NOAA Climate Prediction Center show above-average chances for warm and dry conditions over the drought region extending into summer. La Niña conditions are expected to wane and become neutral by June, but the influence of La Niña on the atmosphere will stay strong through June, keeping the preferred storm track north of Texas and causing below-average rains to the drought region. Real relief from the drought of 2011 will likely only occur when hurricane season starts to get going, bringing moisture-laden tropical disturbances or tropical cyclones to the Texas coast in June and July.

I'll have a new post Thursday or Friday.

Jeff Masters

Fire

Updated: 8:47 PM GMT on April 13, 2011

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Weekend tornado outbreak causes heavy damage in Virginia, Iowa

By: JeffMasters, 2:00 PM GMT on April 11, 2011

Floods, fires, and tornadoes hammered the nation this weekend, a sure sign that April is here. The severe weather action began on Friday night in the mid-Atlantic when twin tornadoes touched down in Pulaski, Virginia. The twisters, one a strong EF-1 with 105 - 110 mph winds, and the other an EF-2 with 125 mph winds damaged 450 buildings, caused $8 million in damage, and injured eight people. The most significant day of the weekend tornado outbreak occurred on Saturday as a powerful storm over the Upper Midwest dragged a cold front through Iowa. Twenty-seven tornado reports were recorded in Iowa by NOAA's Storm Prediction Center. The most powerful of these tornadoes was the huge, 3/4 mile-wide tornado that plowed through the tiny town of Mapleton, Iowa on Saturday evening, leaving a trail of destruction 3.5 miles long. The tornado, preliminarily rated as an EF-3 with 136 - 165 mph winds, flattened 20% of the town of 1200 residents and damaged half of the buildings. Fourteen were injured, but miraculously no one died. The severe weather continued on Sunday with seven reports of tornadoes over Wisconsin. The most serious was a tornado in Lincoln County, which destroyed or heavily damaged 30 buildings, and caused three serious injuries.


Figure 1. Tornado chaser video from Saturday's twisters over Iowa from tornadovideos.net.

More severe weather today
As the cold front that triggered the weekend's severe weather progresses eastwards across the U.S. today, NOAA's Storm Prediction Center has placed a wide swath of the Northeast and Southeast under their "slight" risk area for severe weather, one notch down from the "Medium" risk that was posted for Wisconsin on Sunday and Iowa on Saturday. Tuesday and Wednesday should be relatively quiet days for severe weather, but Thursday will see a renewed chance of a significant severe weather outbreak in the Oklahoma-Arkansas region, as a major new spring storm gathers strength over the Midwest.


Figure 2. Severe weather outlook from NOAA's Storm Prediction Center for Monday places much of the Northeast and Southeast in the "Slight" risk area for severe weather.

Tornado season near average so far this year
According to statistics compiled by NOAA's Storm Prediction Center, 2011's tornado season has been near-average so far. The preliminary number of tornadoes reported as of April 10 was 301, and the six-year average from 2006 - 2010 was 339. Preliminary tornado counts are typically about 15% too high, so the actual number of confirmed tornadoes will end up being around 256. The peak part of tornado season is just getting started--typically, only 17% of the season's activity has occurred by April 10. The number of strong (EF-2 and EF-3) tornadoes has been rather low so far; the Mapleton tornado was just the seventh EF-3 of 2011. There have been no violent EF-4 or EF-5 tornadoes so far this year. The death toll of just three so far in 2011 is remarkably low for mid-April, a testament to good warnings and a good helping of luck.

Jeff Masters

Tornado

Updated: 6:06 PM GMT on April 11, 2011

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Early 2011 Atlantic Hurricane Season Forecasts

By: JeffMasters, 6:22 AM GMT on April 07, 2011

Hi everybody, this is Dr. Rob Carver filling in for Dr. Masters. 

A continuation of the pattern of much above-average Atlantic hurricane activity we've seen since 1995 is on tap for 2011, according to the latest seasonal forecast issued April 6 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). They are calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes. An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast is nearly identical to their forecast made in December, which called for 17 named storms, 9 hurricanes, and 5 intense hurricanes. Only six seasons since 1851 have had as many as 17 named storms; 19 seasons have had 9 or more hurricanes. The 2011 forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The Caribbean is forecast to have a 61% chance of seeing at least one major hurricane (42% is average.) Five years with similar pre-season November atmospheric and oceanic conditions were selected as "analogue" years that the 2011 hurricane season may resemble: 2008, 1999, 1996, 1955, and 2006.  The first four years listed all had neutral to La Niña SST's during hurricane season, while 2006 had El Niño SST's.  The average activity for these years was 12.6 named storms, 7.8 hurricanes, and 4.8 major hurricanes.

This year, the forecasters have introduced a new statistical model for their  April forecasts.  There are four components in this model:

1. Average sea-level pressure in March around the Azores in the subtropical Atlantic.

2. The average of January through March sea-surface temperatures (SST's) in the tropical Atlantic off the coast of Africa.

3. Average sea-level pressure in February and March for the southern tropical Pacific ocean west of South America.

4. Forecasts of September's SST in the tropical Pacific using a dynamical model from the European Centre for Medium-Range Weather Forecasts (ECMWF) 

The first two components are loosely linked together.  Statistical studies have shown that a weaker subtropical high near the Azores, combined with warmer SST's off the coast of Africa in March are associated with weak winds near the surface and aloft from August to October.  This decrease in wind speeds reduces wind shear which can disrupt forming storms.  These March conditions also are associated with warmer SST's in August to October, which is also favorable for more tropical storms.   For this forecast, the first component is strongly favorable for increased hurricane activity, while the second component is weakly negative.

The last two components represent the changes in sea-surface temperature and sea-level pressure that are the El Niño-Southern Oscillation (ENSO).  Briefly speaking,  El Niño conditions (warm sea-surface temperatures) are not favorable for Atlantic hurricanes.  For more info on ENSO and hurricanes, Jeff has this article.

Using the ECMWF model as guidance (see Figure 1), the CSU group believes that SST's in the tropical Pacific will be neutral (less than 0.5°C from normal).  This would have a small negative effect on hurricane activity.  However, the tropical Pacific sea-level pressure shows that the atmosphere looks like a La Niña event is still going on.  This is strongly favorable for Atlantic hurricane activity in the CSU group's model.

Figure 1. Forecasts of El Niño conditions by 20 computer models, made in March 2011. The ECMWF forecast used by the CSU group is represented by the dark orange square.  The forecasts for August-September-October (ASO) show that 5 models predict El Niño conditions, 7 predict neutral conditions, and 5 predict a weak to moderate 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. Image credit: Columbia University.

How accurate are the April forecasts? While the formulas used by CSU do well in making hindcasts--correctly modeling the behavior of past hurricane seasons--their April hurricane season forecasts have had no skill in predicting the future. This year's April forecast is using a new system and has not yet produced a verified forecast.  The scheme used in the past three years successfully predicted active hurricane seasons for 2008 and 2010, but failed to properly predict the relatively quiet 2009 hurricane season. A different formula was used prior to 2008, and the April forecasts using that formula showed no skill over a simple forecast using climatology. CSU maintains an Excel spreadsheet of their forecast errors ( expressed as a mathematical correlation coefficient, where positive means a skilled forecast, and negative means they did worse than climatology) for their their April forecasts. For now, these April forecasts should simply be viewed as an interesting research effort that has the potential to make skillful forecasts. The next CSU forecast, due by June 1, is the one worth paying attention to. Their early June forecasts have shown considerable skill over the years.


Figure 2.
Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Phil Klotzbach and Bill Gray of Colorado State University (colored squares) and Tropical Storm Risk, Inc. (colored lines). The CSU team's April forecast skill is not plotted, but is less than zero. The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H= Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

2011 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.

The  British  private  forecasting  firm  Tropical Storm Risk, Inc.  (TSR),   issued  their  2011  Atlantic hurricane season forecast on April 5. They are also calling for  a  very  active  year: 14. 2 named storms, 7.5 hurricanes, and 3.6 intense hurricanes. We would round that to 14 named storms, 8 hurricanes, and 4 intense hurricanes.   This  compares to their forecast issued in December of 15.6 named storms, 8.4 hurricanes,   and intense hurricanes. TSR predicts a 55%  chance  of  an  above-average  hurricane season, 28% chance of a near-normal season, and only a 17%  chance  of  a  below normal season. TSR bases their April forecast on predictions  that  sea  surface temperatures this fall in the tropical  Atlantic  will  be  above  about  0.08°C above average, and trade  wind  speeds  will  be  about 0.2  m/s  slower  than average.  The decrease in the trade wind speeds is favorable for enhanced hurricane activity, while the forecast SST's are expected to be neutral for hurricane activity.

TSR puts their skill level right next to the forecast numbers: 13% skill above chance at forecasting the number of named storms, 11% skill for hurricanes, and 10% 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.

Rob's critiques of the April forecasts
I have to note that Jeff and I wrote this article together.  He wrote the general framework before the forecasts were issued, while I wrote the details based on the actual forecasts.  So the preceding text is a joint production.  However, I have a few observations to make that are my responsibility alone.

First, I am disappointed that the CSU group has changed forecast models only after three seasonal forecasts.  This makes it very difficult to assess the skill of the current forecast using past performance.  This is very important for forecast users, and they do it everyday.  For example, I tend to discount a forecast of rain if it comes from a source that over-forecasts rain (The boy who cried wolf problem).

In the documentation that came with the April forecast, the CSU group argue that the hindcasts show the new forecast model has skill.  However, I think hindcasts are a poor substitute for real forecasts in understanding the skill of a statistical forecast model, like that of the CSU's group.  As Jeff noted, the previous forecast model did well with the hindcasts and yet had mixed results with the actual forecasts.  This does not give me confidence that the new forecast model will be superior to the previous model.

From a philosophical viewpoint, I am inherently cautious about statistical forecast models like the one used by the CSU group.  Essentially, they look at what happened in the past and use that to predict the future.  However, for making forecasts, we assume that the relationships in space and time between the predictors (such as the average March sea-level pressure around the Azores) and the predictands (Atlantic hurricane activity) does not change as we move forward in time.  In a world with climate change, that's a tricky assumption to make.

In any event, it is customary in the meteorological community to continue running older forecast guidance models after the introduction of newer models.  This allows forecasters and forecast users to leverage their knowledge of the forecast skill of the older model and gain insight into the forecast skill of the new model.  The CSU group really should have included the forecast from the previous statistical forecast system in this forecast.     

I am uneasy with some of the methodology choices made in implementing the forecast model.  Data for the first three predictors was obtained from the Climate Forecast System Reanalysis (CFSR), NOAA's newest and most advanced reanalysis product.  However, CFSR data for 2010 and 2011 has not been released yet, so the CSU group used NCEP/NCAR Reanalysis (NNR), NOAA's first-generation reanalysis, to fill in the gaps.  Due to differences in design, resolution, etc., CFSR and NNR can have different depictions of the state of the atmosphere.  So using NNR's March 2011 average SLP instead of CFSR's could alter the forecast in unexpected ways.  It would be interesting to see how CFSR's 2010-2011 data changes the results. 

In any event, we will have to wait and see what the Atlantic hurricane season of 2011 brings.

Hurricane

Updated: 6:23 PM GMT on August 17, 2011

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The global tropical cyclone season of 2010: record inactivity

By: JeffMasters, 1:14 AM GMT on April 03, 2011

The year 2010 was one of the strangest on record globally for tropical cyclones. Each year, the globe has about 92 tropical cyclones--called hurricanes in the Atlantic and Eastern Pacific, typhoons in the Western Pacific, and tropical cyclones in the Southern Hemisphere. But in 2010, we had just 68 of these storms--the fewest since the dawn of the satellite era in 1970. The previous record slowest year was 1977, when 69 tropical cyclones occurred world-wide. Both the Western Pacific and Eastern Pacific had their quietest seasons on record in 2010, the Atlantic had its 3rd busiest season since record keeping began in 1851, and the Southern Hemisphere had a below average season. As a result, the Atlantic, which ordinarily accounts for just 13% of global cyclone activity, accounted for 28% in 2010--the greatest proportion since accurate tropical cyclone records began in the 1970s. Global Accumulated Cyclone Energy (ACE) for 2010 was the lowest since the late 1970s (ACE is a measure of the total destructive power of a hurricane season, based on the number of days strong winds are observed.)


Figure 1. Visible satellite image of 2010's strongest tropical cyclone: Super Typhoon Megi at 2:25 UTC October 18, 2010. A reconnaissance aircraft measured a central pressure of 885 mb and surface winds of 190 mph in the storm, making Megi the 8th strongest tropical cyclone in world history. Image credit: NASA.

A record quiet 2010 Northwest Pacific Typhoon Season
The Western Pacific set records for fewest number of named storms (fifteen, previous record seventeen in 1998) and typhoons (nine, tied with the previous record of nine in 1998. Note that Tropical Storm Mindulle was upgraded to a typhoon in post-analysis after the season was over.) Reliable records began in the mid-1960s. For just the second year in history, the Atlantic had more named storms and hurricane-strength storms than the Western Pacific. The only other year this occurred was in 2005. Ordinarily, the Western Pacific has double to triple the amount of tropical cyclones of the Atlantic. One other notable feature of the 2010 season was the lack of a land-falling typhoon on the Japanese mainland. This is only the second such occurrence since 1988.

In 2010, there was only one super typhoon--a storm with at least 150 mph winds--in the Western Pacific. However, this storm, Super Typhoon Megi, was a doozy. Megi's sustained winds cranked up to a fearsome 190 mph and its central pressure bottomed out at 885 mb on October 16, making it the 8th most intense tropical cyclone in world history. Fortunately, Megi weakened significantly before hitting the Philippines as a Category 3 typhoon. Megi killed 69 people on Taiwan and in the Philippines and did $700 million in damage, and was the second deadliest and damaging typhoon of 2010. Category 3 Typhoon Fanapi was the deadliest and most damaging typhoon of 2010, doing over $1 billion in damage to Taiwan and China and killing 105.

The record quiet typhoon season in 2010 was due, in part, to the La Niña phenomena. During such events, the formation region for Western Pacific typhoons moves northwestward, closer to China. Thus, storms that form in the Western Pacific spend less time over water before they encounter land, resulting in a lesser chance to become a named storm, and less time to intensify. They also accumulate a lower ACE due to their shorter duration. Since the Western Pacific is responsible for 35% of the world's major tropical cyclones, the global ACE value is strongly tied to year-to-year variations in the El Niño/La Niña cycle.


Figure 2.
Statistics for the global tropical cyclone season of 2010. The two numbers in each box represent the actual number observed in 2010, followed by the averages from the period 1983-2007 (in parentheses). Averages and records were computed using the December 23, 2008 release of NOAA's International Best Track Archive for Climate Stewardship.

A record quiet 2010 Eastern Pacific Typhoon Season
In the Eastern Pacific, it was also a record-quiet season. On average, the Eastern Pacific has 15 named storms, 8 hurricanes, and 3 intense hurricanes in a season. In 2010, there were 8 named storms, 3 hurricanes, and 2 intense hurricanes. The previous record quietest season since 1966 was the year 1977, when the Eastern Pacific had 8 named storms, 4 hurricanes, and zero intense hurricanes. La Niña was largely responsible for the quiet Eastern Pacific hurricane season, due in part to the cool sea surface temperatures it brought. It is quite remarkable that both the Eastern and Western Pacific ocean basins had record quiet seasons in the same year--there is no historical precedent for such an occurrence.

Climate change and the 2008 global tropical cyclone season
We only have about 30 years of reliable global tropical cyclone data, and tropical cyclones are subject to large natural variations in numbers and intensities. Thus, it will be very difficult at present to prove that climate change is affecting global tropical cyclone activity. (This is less so in the Atlantic, where we have a longer reliable data record to work with.) A common theme of many recent publications on the future of tropical cyclones globally in a warming climate is that the total number of these storms will decrease, but the strongest storms will get stronger. For example, a 2010 review paper published in Nature Geosciences concluded: "greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2 - 11% by 2100. Existing modeling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6 - 34%. Balanced against this, higher resolution modeling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre." Last year, I discussed a paper by Bender et al that concluded that the total number of Atlantic hurricanes is expected to decrease by the end of the century, but there could be an increase of 81% in the number of Category 4 and 5 storms. The net effect of a decrease in total number of hurricanes but an increase in the strongest hurricanes should cause an increase in U.S. hurricane damages of about 30% by the end of the century, the authors computed, assuming that hurricane damages behave as they did during the past century. A new paper just published by Murakami et. al predicts that Western Pacific tropical cyclones may decrease in number by 23% by the end of the century, primarily due to a shift in the formation location and tracks of these storms.

In light of these theoretical results, it is interesting that 2010 saw the lowest number of global tropical cyclones on record, but an average number of very strong Category 4 and 5 storms. Fully 21% of last year's tropical cyclones reached Category 4 or 5 strength, versus just 14% during the period 1983 - 2007. Most notably, in 2010 we had the second strongest tropical cyclone on record in the Arabian Sea (Category 4 Cyclone Phet in June) and the strongest tropical cyclone ever to hit Myanmar/Burma (October's Tropical Cyclone Giri, an upper end Category 4 storm with 155 mph winds.) It is too early to read anything into this year's global tropical cyclone numbers, though--we need many more years of data before making any judgments on how global tropical cyclones might be responding to climate change.


Figure 3. Visible satellite image of Tropical Cyclone Phet on Thursday, June 3, 2010. Record heat over southern Asia in May helped heat up the Arabian Sea to 2°C above normal, and the exceptionally warm SSTs helped fuel Tropical Cyclone Phet into the second strongest tropical cyclone ever recorded in the Arabian Sea. Phet peaked at Category 4 strength with 145 mph winds. Only Category 5 Cyclone Gonu of 2007, which devastated Oman, was a stronger Arabian Sea cyclone. Phet killed 44 people and did $700 million in damage to Oman.


Figure 4. Visible MODIS satellite image of Tropical Cyclone Giri taken at 2:55am EDT October 22, 2010, just prior to landfall in Myanmar/Burma. At the time, Giri was a Category 4 storm with 145 mph winds. Giri killed 157 people and did $359 million in damage. Image credit: NASA.

Jeff Masters

Hurricane

Updated: 5:03 PM GMT on April 19, 2011

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Jeopardy champion WATSON appointed head of National Academy of Blog Science

By: JeffMasters, 4:14 AM GMT on April 01, 2011

Jeopardy champion WATSON--the computer program that earlier this year decisively beat the two all-time human champions of America's favorite game show--has a new challenge. A modified version of WATSON has been appointed to direct a major new scientific organization, the White House announced today. The WATSON spin-off, dubbed HOLMES (short for Highly Objective Lore Machine for Examining Science), will head the newly created National Academy of Blog Science (NABS). The NABS, created in legislation passed by Congress last week, will replace the prestigious National Academy of Sciences (NAS) as the premier scientific advisory organization in charge of advising Congress on scientific matters. "The creation of the National Academy of Blog Science is a huge step forward for America's businesses to help them become more competitive and create jobs," said U.S. House of Representatives Speaker John Bayinghound, who pushed the legislation through Congress.



Figure 1. HOLMES' predecessor, WATSON, clobbering the two all-time Jeopardy champions in a match earlier this year.

Dr. Hal N. Thousand, chief scientist for the Very Competitive Free Enterprise Institute (VCFEI), the pro-business think tank that crafted the legislation to create the NABS, lauded the choice of HOLMES to head the new advisory body. "The old National Academy of Sciences used archaic methods to determine the best science, relying exclusively on peer-reviewed publications. In the peer-review system, papers undergo a lengthy review process by multiple experts in the field, followed by revisions, followed by further review, finally ending in rejection or publication in a prestigious scientific journal. Ignored in the process is the tremendous amount of excellent non-peer-reviewed science published in blogs and in industry publications. HOLMES, once interfaced with the Internet, has the capability to search through all these relevant scientific works and rank the best science with a percentage probability of correctness--just like WATSON did during the Jeopardy championships. If there are popular blogs or a large body of corporate science challenging peer-reviewed scientific findings as being too uncertain, HOLMES will lower the probability of the peer-reviewed scientific result being correct. Thus, the advice given by NABS to Congress will be far more reasonable, taking in a wider range of opinions than those previously considered by the outdated National Academy of Sciences. Grant-based anti-industry "science" developed in ivory towers will no longer be accepted unquestioningly at the cost of jobs. The American tax payer can't afford it. This is the way a scientific advisory body should behave, since any scientific results that hurt corporate profits and thus jobs should be required to be virtually certain. Too often, this country has been misled by science harmful to American business interests, pushed by elitist, alarmist, money-grubbing scientists, out to pad their research grants by falsely crying wolf. It's time to cast down the high priests of this America-hating eco-religion, and let HOLMES, who is incapable of bias, make the decisions on what is the best science."

Dr. Frank Poole, spokesman for the Coalition of Environmental Organizations Against Insanity, who lobbied fervently against the new National Academy of Blog Science, commented: "It is ludicrous to put a computer that thought Toronto was a city in the U.S. during Final Jeopardy in charge of the world's most important scientific advisory body. WATSON also thought Wonder Woman was the first woman in space. This does not bode well for the future of American policy to be based on the best science."

Dr. Thousand countered that the new HOLMES computer would be unlike its predecessor, WATSON. "In the coming months, under HOLMES' new clear vision of science fact, the people will see the peer-review system of science for the corrupt farce that it is, and demand that it be abolished. We are already crafting new legislation to remove all government funding for scientific research that HOLMES judges to be anti-corporate, including all money for climate change research and for the Environmental Protection Agency. That kind of research must be done by concerned citizen-bloggers and by the corporations who might be affected by the scientific findings. Science in this country must be done the democratic way--every citizen will be able to weigh in on their favorite blog site and vote for what they think is the best science. HOLMES, with the aid of an adaptive scientific truth algorithm we are developing, will be able to use the will of the people and the best corporate and blog science to advise Congress on scientific matters, and a brave new world of science-based policy will be born."

April Fools! (I hope)

Jeff Masters

Humor

Updated: 11:17 PM GMT on August 16, 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.