NOAA's National Centers for Environmental Information
It should be noted, due to the extreme nature of the tornado activity this month, that it will take several months for the count of tornadoes and tornado-related fatalities/injuries to be finalized. Numbers reported here will likely change in the coming months. A special report on all of the extreme weather and climate conditions of April 2011 will be released by early summer 2011.
Significant April 2011 Tornado Outbreaks:
April 2011 was one of the most active, destructive, and deadly tornado months on record for the United States, and could become the benchmark that future months will be compared to. According to data from the Storm Prediction Center (SPC), there were 875 preliminary tornado reports during the month, and the final tornado count will approach the all-time monthly record of 542 tornadoes after all storm surveys are completed. The previous April record was 267 tornadoes, which occurred in April 1974, and the record for any month was May 2003, when there were 542 confirmed tornadoes. The 30-year average for number of April tornadoes is 135. It should be noted that many of the tornadoes that occurred during April 2011 have been rated weak (EF-0 and EF-1), consistent with improved detection and verification methodologies used by the National Weather Service in recent years.
The tornado-related death toll for April 2011 currently stands at 369 people, with tens of thousands of injury reports. It is likely the count of tornado-related fatalities will rise as more complete storm surveys become available. This is the most monthly tornado fatalties since the Doppler radar network was deployed in the early 1990s. The SPC will continue to provide the most up-to-date tornado numbers, and readers can check their website for updated information. Although the death toll this month was staggering, the average warning lead time on these tornadoes, issued by the National Weather Service, was 24 minutes, which undoubtedly saved many lives in the affected regions. During the month of April, there were several significant, multi-day tornado outbreaks to impact the country, which are discussed below. The hardest hit areas included the Southern Plains, the Southeast, the Ohio River Valley and the Mid-Atlantic. The tornado damage for the month will exceed two billion U.S. dollars, and may potentially reach five billion U.S. dollars.
Significant Events
April 4th
The first major tornado outbreak of the month was on April 4th when a powerful upper level low pressure system moved across the Great Plains and Mississippi River Valley. The storm system was associated with record breaking warm temperatures as it pulled warm, moist air from the Gulf of Mexico into the mid-South, creating unstable atmospheric conditions. A very large and fast moving squall line formed ahead of the low which moved across the southeastern quadrant of the country, bringing severe weather from Texas to Pennsylvania. Many of the storms within the squall line became severe and produced tornadoes. The line of storms traveled more than 800 miles (1,290 km) in about 24 hours with an average speed of 30-40 mph (48-65 km/hr). The storm was associated with 68 preliminary tornado reports, 1318 preliminary severe wind reports, and 90 hail reports. While the outbreak produced a large number of tornadoes, they were not very strong, limiting the amount of damage. More impressive was the number of severe wind reports, which after the local National Weather Service offices investigate, will likely be record breaking. The previous record for one-day severe wind reports was 455 on April 2nd, 2006. See Global Hazards for more information.
April 9th
On April 9th and 10th, a storm system moved from South Dakota to northern Wisconsin, colliding with warm, moist air. As the associated cold front moved into the warm and moist environment over Wisconsin and Iowa, it initiated severe thunderstorms across the two states. During the two day outbreak, there were 56 preliminary tornado reports. In Iowa, a strong EF-3 tornado hit Mapleton, which demolished the western portion of the town and injured 14 people. On the 10th, there were 14 confirmed tornadoes across Wisconsin, with four being classified as strong (EF-2 and EF-3). This marked the first April tornado outbreak in the state in 17 years, and the first strong tornadoes to hit Wisconsin in 27 years during the month of April. This outbreak was the largest April tornado outbreak to ever affect the state, and the sixth largest of any month. The state averages 20 tornadoes annually. The tornadoes impacted relatively rural areas, which limited the amount of damage done, however storm assessments were still being conducted at the time this report was written.
April 14th–16th
On April 14th–16th, a strong upper level low pressure system moved across the central Plains. Ahead of the low pressure system, very warm and very moist air was pulled northward across the southeastern U.S., priming the atmosphere for severe weather. Behind the system, cool Canadian air filtered into the central region of the country. As the associated cold front moved through the region, the collision between the two air masses triggered a massive severe weather outbreak from Oklahoma to the Carolinas in a 3-day violent weather blitz. Over the course of the three days, there were 329 preliminary tornado reports across 16 states. NOAA estimates the final tornado count for the outbreak will be about 155 tornadoes, marking one of the largest on record, especially for April which averages 135 tornadoes for the entire month.
On the first day of the outbreak, April 14th, there were 38 preliminary tornado reports across the Southern Plains, with Oklahoma and Arkansas being the hardest hit. Two people were killed by an EF-3 tornado which tore through Tushka in eastern Oklahoma. Two fatalities were also reported in Pulaski County, Arkansas. As the storm system moved eastward, it trigged another round of severe weather on the 15th across the Gulf Coast states. There were 146 preliminary tornado reports across the region, with Mississippi and Alabama being the hardest hit. Over 100 people were reported injured by the storms which caused tens of millions of dollars worth of damage in the two states. In Greene County, Mississippi an EF-3 tornado caused a fatality when it destroyed a mobile home. The same tornado then moved into Alabama where it killed another three people in Deer Park. The tornado also crossed Interstate Highway 20 tossing numerous cars and forcing the interstate to be closed for hours. Another fatality was reported in Boones Chapel, Alabama where an EF-3 brought winds of 150 mph (241 km/hr), destroying 50 homes. On the 16th, the storm system progressed into the Southeast, where there were 139 preliminary tornado reports across the Mid-Atlantic. In North Carolina, there were at least 30 confirmed tornadoes, which killed 24 people and destroyed hundreds of homes across the state. This marks the largest tornado outbreak to ever hit the state, and the second deadliest outbreak on record for North Carolina. An EF-3 tornado tracked 63 miles (101 km) across the central part of state and hit downtown Raleigh, causing widespread damage to the capital city. Twelve people were killed in Askewville, North Carolina when an EF-3 tornado ripped through the town. Two deaths were reported in southwestern Virginia on the same day as the storms moved off to the northeast.
In all, this tornado outbreak was one of the most significant outbreaks to ever affect the country to-date. States of emergencies were declared in Alabama, Mississippi, Oklahoma, and North Carolina, allowing federal funds to be used in rebuilding the affected communities. The total fatality count for the entire outbreak reached 38, marking the deadliest tornado outbreak for the country since February 2008. Once the number of tornadoes is confirmed, it is likely that the outbreak will be one of the largest April outbreaks on record, and one of the largest to occur during any month.
April 19th
On April 19th, severe thunderstorms formed ahead of a strong cold front moving through the Midwest and Ohio River Valley, causing a significant tornado outbreak across the region. The storms were associated with 77 preliminary tornado reports, mostly in Illinois, Indiana, Ohio, and Kentucky. The storms were also associated with 357 hail reports and 575 severe wind reports. Straight line winds associated with downbursts caused significant damage in southwestern Indiana. Several of the tornadoes were rated EF-2 and EF-3, and caused damage to homes and businesses in the region. Fortunately there were few reports of injuries, and no reports of fatalities associated with the tornadoes.
April 22nd
On April 22nd, Good Friday, two supercell thunderstorms crossed the St. Louis Metropolitan area bringing large hail, strong winds, and an EF-4 tornado to the city. The EF-4 tornado ripped a 21 mile (34 km) path across St. Louis County, Missouri and jumped the Mississippi River into Madison County, Illinois where it dissipated. The worst damage occurred in the northwestern parts of St. Louis, when the tornado hit the Lambert St. Louis International Airport, the world’s 30th busiest airport. Many windows were blown out of the airport, and large pieces of the roof were blown off. Due to tornado warnings issued by the National Weather Service, many portions of the airport had been evacuated, limiting the number injuries and preventing loss of life. Due to structural damages, the airport was forced to close for several hours, but was fully operational again by April 26th.
April 25th–28th
Between April 25th and 28th, one of the largest, deadliest, and most destructive tornado outbreaks in U.S. history struck the eastern third of the nation. A strong upper level low pressure system moved across the northern Plains and the associated cold front tapped into a very moist and unstable atmosphere, producing an extraordinary tornado outbreak across the southeastern United States. NOAA’s preliminary estimate is that there were 305 tornadoes that hit from Texas to New York, with an estimated 190 tornadoes touching down over a 24-hour period on the 27th and 28th. At the time this report was released in early May, storm surveys continued to be conducted and the final tornado counts as well as fatalities/injuries continued to be unresolved. However, the current count of strong tornadoes was three EF-5s, 12 EF-4s, and 21 EF3s. In comparison, the April 1974 Super Outbreak had six F-5s, 23 F-4s, and 35 F-3s.
Preliminary analysis places the death toll near 350 people for the entire outbreak, mostly across the state of Alabama. This surpasses the death toll and tornado counts of the April 1974 super outbreak, which had 148 tornadoes and 315 deaths associated with it. One of the EF-5 tornadoes of the outbreak occurred across northern Mississippi, near Smithville. The tornado had estimated winds of 205 mph (330 km/hr), destroyed 18 homes, and killed 14 people. This was the first EF-5 tornado since the tornado that struck Parkersburg, Iowa in February 2008. The second EF-5 tornado of the outbreak occurred across northern Alabama and southeastern Tennessee. The tornado had a continuous path length of 132 miles (212 km) and was up to 1.25 miles (2 km) wide at certain points. Thousands of homes and other structures were destroyed or heavily damaged. The number of fatalities and injuries were unknown. The most destructive tornado of the outbreak occurred across central Alabama, hitting the cities of Tuscaloosa and Birmingham, and was deemed a strong EF-4. The violent tornado had winds of up to 190 mph (306 km/hr), a maximum path width of 1.5 miles (2.4 km), and was on the ground for approximately 80.3 miles (129 km). Preliminary estimates report there were over a thousand injuries and 65 fatalities with this single tornado. In Tuscaloosa alone, it is estimated that it will cost up to 100 million US dollars just to remove debris from the city. These numbers will likely be revised upwards, once the final surveys are completed. This tornado could potentially surpass the F-5 tornado which hit Moore, Oklahoma in May 1999 as the most expensive tornado to ever hit the United States. The supercell thunderstorm that spawned this tornado tracked over 380 miles (612 km) from Mississippi to North Carolina, spawning several tornadoes along its way. According to analysis by NOAA, this tornado was the deadliest tornado since May 25, 1955 when 80 people were killed by a tornado in Kansas.
The outbreak has a whole also produced staggering fatality statistics. The April 26-28, 2011 period had the most people killed during a single tornado outbreak since 454 people were killed in the April 5-6, 1936 tornado outbreak. April 27, 2011 marks the deadliest tornado day since March 18, 1925 when 747 people were killed by tornadoes. Additional information on individual tornadoes and the outbreak can be found through the following links: