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NOAA releases statistics highlighting devastating April tornado outbreak

Monday, May 16th, 2011 7:17pm MDT
Tornado Tracks: April 24th through the 29th, 2011. (NOAA)

Tornado Tracks: April 24th through the 29th, 2011. (NOAA) Click the image for a larger view.

The devastating tornado outbreak that struck across the southern United States last month continues to be analyzed by the National Weather Service.  At latest county 326 people were killed and as many as 305 tornadoes resulted in in the outbreak.

What follows is NOAA’s latest update on the events:

From NOAA:

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 preliminary 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 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.
Preliminary Tornado Data Table
Date Eyewitness Reports NOAA’s Estimate Tornadoes Surveyed by WFOs (to date)
25-26 55 40 25
26-27 111 75 42
27-28 268 190 134
Total: 434 305 201

  • 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.
  • The largest previous number of tornadoes on record in one event occurred from April 3-4, 1974, with 148 tornadoes.
  • NOAA will conduct a detailed analysis of tornado numbers using all available data to make any final determinations about records.  This typically takes months to complete.

There were approximately 326 fatalities during the entire outbreak from April 25 to April 28.

There were approximately 309 fatalities during the 24-hour-period from 8:00 a.m. April 27 to 8:00 a.m. April 28. This is currently the fifth deadliest day of tornadoes on record.

  • 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.

According to National Weather Service Weather Forecast Office Storm Survey teams, there were 24+ killer tornadoes in six states–Arkansas, Mississippi, Alabama, Georgia, Tennessee and Virginia–that caused an estimated 326 fatalities.

The National Weather Service Storm Survey teams have upgraded to EF-5 the tornado that hit Neshoba, Kemper, Winston, Noxubee Counties in Mississippi.  The Weather Service has documented three (3) EF-5 tornadoes in this outbreak.

EF-5 Tornado Locations

  • Northern Mississippi/Eastern Arkansas
    • Smithville in Monroe County
  • Mississippi (NEWLY UPGRADED TO EF-5 FROM E-4)
  • Northern/Central Alabama (WFO Birmingham Warning Area):
    • Hackleburg in Marion County

The following are the tornado fatality breakdowns by state:

  • 4 – Arkansas
  • 35 – Mississippi
  • 236 – Alabama
  • 31 – Tennessee
  • 5 – Virginia
  • 15 – Georgia

Note:  All numbers are based on combined NOAA and historical research records and current fatality estimates. The historical research records extend back to 1680.

Ongoing (preliminary) List of Tornadoes by EF Rating (EF0 to EF5):
EF-5 3
EF-4 11
EF-3 21
EF-2 47
EF-1 62
EF-0 57
Total: 201

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