April's tornado outbreaks the two largest in history

The largest tornado outbreak and greatest one-day total for tornadoes in history occurred during last week's historic super tornado outbreak, said NOAA in a press release on Wednesday. They estimate 190 tornadoes touched down during the 24-hour period from 8:00 a.m. EDT April 27 to 8:00 a.m. EDT April 28 (132 tornadoes have already been confirmed, with several weeks of damage surveys still to come.) NOAA's estimate for the number of tornadoes during the three-day April 25 - 28, 2011 Super Outbreak, is 305. This is nearly double the previous record for a multi-day tornado outbreak of 155 tornadoes, set just two weeks previously during the April 14 - 16, 2011 outbreak. There were tornado outbreaks in May 2004 (385 tornadoes) and May 2003 (401 tornadoes) that had more tornadoes, but these outbreaks occurred over an eight-day and eleven-day period, respectively, and were not due to a single storm system. Prior to April 2011, the most tornadoes in a 24-hour period, and in an outbreak lasting less than four days, was the 148 tornadoes in the Super Outbreak of April 3 - 4, 1974.



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



Figure 2. Preliminary tornado tracks from NWS survets for the April 27, 2011 tornado outbreak. Image credit: NWS Southern Region.

The death toll for the epic outbreak continues to fluctuate, and has decreased substantially to 318. The count decreased in Alabama from 250 to 236 due to some of the victims being counted twice. There are still hundreds of people missing from the tornado, and search teams have not yet made it to all of the towns ravaged by the tornadoes. The estimated 318 deaths makes this is the 4th or 5th deadliest tornado outbreak on record. Only the great Tri-State tornado outbreak of 1925 (747 killed), the 1936 Tupelo-Gainsville tornado outbreak (454 killed), and a 1932 outbreak (332 killed) had more deaths.

Other notable facts from the great April 25 -28, 2011 tornado outbreak
The Tuscaloosa-Birmingham tornado is likely to be the most expensive tornado of all-time, and damage from the April 25 - 28 outbreak is the most expensive tornado outbreak in history. Insured damages have been rated at $2 - $5 billion, and uninsured losses will be several billion more. The previous most expensive tornado outbreak in history was the $3.5 billion price tag, in 2005 dollars, of the April 3 - 4, 1974 Super Outbreak .

The Tuscaloosa-Birmingham tornado caused at least 65 fatalities. This tornado had a maximum width of 1.5 miles and a track 80 miles long. These are the most fatalities from a single tornado in the United States since May 25, 1955, when 80 people were killed in a tornado in southern Kansas with 75 of those deaths in Udall, Kansas.

NOAA estimates there were more than 600 tornadoes during the month of April 2011, shattering previous records. The previous April tornado record was 267, set in 1974. April has averaged just 161 tornadoes over the past decade. The previous record number of tornadoes during any month was 542, set in May 2003. So far there have been an estimated 881 tornadoes in 2011. The annual tornado record is 1,817, set in 2004. May is historically the most active month for tornadoes.

So far, 2011 is the 13th deadliest year for tornadoes on record with 369, and the deadliest year since the advent of Doppler radar in late 1980s and 1990s. The deadliest year on record is 1925 with 794.

The outbreak had fourteen violent tornadoes--two EF-5s (the Smithville, MS tornado, and the Hackleburg, AL tornado), and twelve EF-4s. The Super Outbreak of 1974 had far more violent tornadoes, with an unprecedented seven F5s and 23 F4s.

National Weather Service forecast offices provided plenty of warning for the tornadoes, issuing life-saving tornado warnings with an average lead-time of 24 minutes. Warnings were in effect for more than 90 percent of the tornadoes.


Figure 3. Youtube video of the Tuscaloosa-Birmingham tornado of April 27, 2011, as it hit Birmingham.

The most violent tornado of the outbreak: the 210-mph Hackleburg tornado
The most violent and longest-lived tornado of the great April 26 - 28, 2011 outbreak was the Hackleburg tornado. This tornado initially touched down in Northwest Alabama near the Mississippi border, then roared to the northeast for 132.1 miles into Tennessee, causing EF-5 damage at many locations along its path. The most significant damage occurred in the town of Phil Campbell, wind in excess of 200 mph sucked up a 25-foot section of pavement and scattered it up to 1/3 mile away. Tornadoes that can suck up pavement are a rare breed, earning this twister its EF-5 rating. The tornado intensified even further as it hit the town of Oak Grove, where winds estimated at 210 mph over a swath more than one mile wide completely destroyed many buildings, tossed a Corvette 641 feet, and tossed another large car so far that it has not yet been found.

A list of the pages at each National Weather Service forecast office on the tornadoes from the April 25 - 28 outbreak that affected their area (posted by wunderground member beell, thanks!):

Birmingham, AL
Huntsville, AL
Mobile, AL
Little Rock, AR
Tallahasse, FL
Atlanta, GA
Louisville, KY
Paducah, KY
Shreveport, LA
Jackson, MS
Albany, NY
Binghamton, NY
Wilmington, OH
State College, PA
Columbia, SC
Greenville, SC
Memphis, TN
Morristown, TN
Nashville, TN
Dallas, TX
Blacksburg, VA
Sterling, VA
Wakefield, VA

All-time Mississippi River flood records fall
This week, for the first time in 74 years, the Army Corps of Engineers was forced to intentionally destroy the Birds Point levee on the west bank of the Mississippi River, just downstream from the river's confluence with the Ohio River at Cairo, Illinois. The Ohio River at Cairo, Illinois continues to fall this morning, thanks to this emergency operation, with a level two feet below the all-time peak of 61.8' set on Monday night. The destruction of the Birds Point levee also helped slow the rise of the Mississippi River just south of its confluence with the Ohio River, but the river is still rising slowly, and has now set all-time records at New Madrid, Missouri, Tiptonville, Tennessee, and Caruthersville, Missouri--a 70-mile stretch of river downstream from Cairo. The massive pulse of flood waters will continue downstream for the next 2 - 3 weeks, setting all-time flood records at many locations. The National Weather Service in Jackson, Mississippi has created a nice "May 2011 Mississippi River Flood" web page that details the current stages, expected crests, and previous record crests along the river's path. Currently, the Mississippi is expected to reach its 2nd highest level on record at Memphis on May 11, beat the all-time record at Vicksburg, Mississippi by 1.3' on May 20, and smash the all-time record at Natchez, Mississippi by six feet on May 22. I'll be saying much more about this unprecedented Mississippi flood on Friday, and throughout the month of May.


Figure 4. The Portlight relief trailer being loaded in Summerville, SC, in preparation for a journey to the tornado disaster zone.

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. They have been very active in this disaster, bringing aid to many of the victims of this great tragedy.

Jeff Masters