NOAA’s preliminary estimate is that there were 305 tornadoes during the entire outbreak from 8:00 a.m. EDT April 25 to 8:00 a.m. April 28, 2011. NWS created a table to provide clearer insight into the number of tornadoes. Each of the three categories in the table below has different levels of confidence/accuracy.
- Eyewitness Reports are the least accurate/reliable because with long-lived tornadoes like those in this outbreak tend to be reported multiple times. This artificially increases the number of tornadoes.
- NOAA’s Estimate is based on expert analysis of the Eyewitness Reports compared with the details coming out of the Tornadoes Surveyed by NWS Weather Forecast Offices (WFO). It is the statistic NWS uses in public announcements since it is the best estimate at the time. The numbers will change (typically down) as WFOs complete their storm surveys.
- Tornadoes Surveyed by WFOs is the latest confirmed number of tornadoes surveyed by the National Weather Service. When all storm surveys are complete this is the number that will go into the permanent record as the actual number.
|Preliminary Tornado Data Table|
|Date||Eyewitness Reports||NOAA’s Estimate||Tornadoes Surveyed by WFOs (to date)|
- The NWS Storm Prediction Center issued severe weather outlooks five days in advance and tornado watches hours in advance.
- NWS Weather Forecast Offices issued life-saving tornado warnings, with an average lead-time of 24 minutes. NWS issued warnings for more than 90 percent of these tornadoes.
- NWS decision support for this event has been extensive. NWS Weather Forecast Offices in the affected areas of Arkansas, Tennessee, Mississippi, Alabama and Georgia advertised the potential for severe weather in the Tuesday through Wednesday timeframe since late last week. Local offices provided direct decision support services to meet the specific needs of local emergency manager partners and the general public. NWS Weather Forecast Offices issued Hazardous Weather Outlooks up to six days in advance noting the greater threat of strong, long-track tornadoes was expected.
Data is preliminary and subject to revision
The largest previous number of tornadoes on record in one event occurred from April 3-4, 1974, with 148 tornadoes.
There were 340 fatalities during the 24-hour-period from 8:00 a.m. April 27 to 8:00 a.m. April 28.
- The Tuscaloosa-Birmingham tornado during the April 2011 event 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.
- The deadliest single tornado on record in the United States was the Tri-State tornado (Mo., Ill., Ind.) on March 18, 1925, when 695 died.
Ongoing (preliminary) List of Tornadoes by EF Rating (EF3 to EF5):
- EF5: 2
- EF4: 11
- EF3: 21
Note: All numbers are based on combined NOAA and historical research records and current fatality estimates. The historical research records extend back to 1860.