The April 27-28, 2011 tornado outbreak (part of the larger 2011 Super Outbreak) was one of the most devastating and deadly severe weather events in Georgia history. It produced dozens of tornadoes across north and central Georgia on April 27 and 28, 2011, killing at least 20 people in the state, injuring hundreds, and causing widespread destruction. This was the deadliest tornado outbreak in Georgia since the 1936 Tupelo–Gainesville outbreak and remains the benchmark for spring severe weather in the region. The outbreak was driven by a powerful spring storm system with extreme instability, strong shear, and abundant moisture.

Meteorological Setup

A deep upper-level trough dug into the central/eastern U.S., with a strong surface low tracking from the Southern Plains through the Mississippi Valley. A warm, moist air mass from the Gulf of Mexico surged northward ahead of a cold front, creating extreme instability (CAPE values 2000–4000 J/kg) and strong wind shear (deep-layer shear 50–70+ knots). The setup was classic for a major tornado outbreak: high CAPE + strong directional shear + dryline/cold front forcing. The most intense tornadoes occurred on April 27 afternoon/evening as discrete supercells formed along the dryline and cold front, then evolved into a squall line overnight into April 28.

Tornado Summary for Georgia

Major Tornadoes and Tracks in Georgia

Impacts in North Georgia

Legacy and Significance

This tornado outbreak is now the 2nd deadliest in U.S. history.

This is a link to the CDC report: Tornado-Related Fatalities — Five States, Southeastern United States, April 25–28, 2011

 

April 27-28, 2011, Tornado Outbreak Statistics

• NOAA's preliminary estimate is that there were 362 tornadoes during the entire outbreak from 8:00 a.m. EDT April 26 to 8:00 a.m. April 28, 2011.
• During the 24-hour period from 8:00 a.m. EDT April 27 to 8:00 a.m. EDT April 28, The National Weather Service (NWS) estimates there were a total of 305 tornadoes.
• The largest previous number of tornadoes on record in one event occurred from April 3-4, 1974, with 148 tornadoes.
• NWS issued outlooks five days in advance, watches hours in advance, and tornado warnings with an average lead time of 24 minutes.
• By 10:17pm on the 27th, more than 337 tornado warnings had been issued that day with more than 80 by the Huntsville NWS office alone. Both the Huntsville and Birmingham offices of the NWS had to evacuate their offices during the day.
• NWS issued warnings for more than 90 percent of these tornadoes.
• Expert NOAA analysis of the fatality information indicates that at least 326 people were killed during the entire outbreak from 8:00 a.m. EDT April 25 to 8:00 a.m. April 28. There were 309 fatalities during the 24-hour-period from 8:00 a.m. April 27 to 8:00 a.m. April 28. This makes the event the second deadliest tornado outbreak on record and the 5th deadliest tornado day on record. The April 27-28, 2011, tornado outbreak is now deadlier than the March 21, 1932, tornado outbreak that had 332 fatalities, which ironically occurred in Alabama also.
• This is the most people killed by tornadoes in a two-day period since April 5-6, 1936, when 454 people were killed, mostly in Tupelo, Mississippi and Gainesville, Georgia.
• Based on combined NOAA, historical research records and current fatality estimates, the April 27-28, 2011, tornado outbreak ranks 5th in single day total fatalities in the United States history. The historic research records extend back to 1680.
• 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 timeframebeginning the week before. 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 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 was the Tri-State Tornado (Mo., Ill., Ind.) on March 18, 1925, when 695 died. Based on combined NOAA and historical research records, the deadliest single day for tornadoes was March 18, 1925, with 747 fatalities across 7 states (including the Tri State Tornado).
• The current count is:
• EF5: 3
• EF4: 11
• EF3: 21
• EF2: 47
• EF1: 62
• EF0: 57

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

In addition to the violence of these tornadoes, the long-track nature of these tornadoes indicates just how powerful and steady-state some of these mesocyclones were. The Raleigh/Snell, MS track just got extended into BMX's territory - that tornado was on the ground for 123 miles, the third such >100 mi path length tornado during the outbreak. Hackleburg/Phil Campbell/Tanner measures in at 132 mi, and Cordova at least 104 mi. Other notable long path lengths: Calhoun-St. Clair 98 mi (AL+GA combined), BHM 80 mi, Eoline 71 mi. Together these five tornadoes traveled a total of 608 mi on the ground.

Month of April 2011 (and record monthly) tornado statistics

NWS’s now estimates there were 875 tornadoes during the month of April 2011 which is now an all time record for any month.

• The previous record number of tornadoes during the month of April was 267 tornadoes set in April 1974.
• The previous record number of tornadoes during any month was 542 tornadoes set in May 2003.
• The average number of tornadoes for the month of April during the past decade is 161.
• The overall monthly average number of tornadoes for the past decade is 106.

2011 Year-to-Date (and record annual) statistics

• NWS’s preliminary estimate is that there have been 835 tornadoes so far this year.
• The previous yearly record number of tornadoes was set in 2004 with 1,817.
• May is historically the most active month for tornadoes.
• The overall yearly average number of tornadoes for the past decade is 1274.

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Storm Survey Results from SE NWS Offices

This is a listing from the various NWS offices around the southeast.

• Huntsville AL (HUN)
• Jackson MS (JAN)
• Raleigh NC (RAH)
• Birmingham AL (BMX)

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Synopsis

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On April 27th, 2011 a strong cold front with several areas of embedded low pressure was pushing into central Arkansas and Eastern Texas. Warm moist air was evident due to strong southerly flow ahead of this front over Mississippi, Alabama, Georgia, and Tennessee. This can be seen on the surface map below with the 62 to 66 degree dewpoints over these areas. A disturbance extending southeast from the one of these lows over southern Illinois pushing east was enhancing the lift and producing a line of severe thunderstorms across Mississippi. This disturbance provided strong wind energy and wind shear, as winds at 850 mb increased to between 50 and 55 knots and became more southerly. This combination of high low level moisture and increasing shear provided the potential for damaging winds, large hail and tornadoes. In fact, as this line pushed into northern Alabama, 0 to 6 km shear increased drastically to between 500 and 1000 m2/s2. This line pushed further east into northwestern Alabama quickly after 4:00 AM. Surface conditions can be seen in the image below over the south at this time.

High Shear and moist surface conditions continued throughout the day and into the evening ahead of the strong approaching cold front. This combination of strong instability and high shear continued through the evening hours ahead of the cold front before it pushed east of the area into Georgia during the late evening hours. Below is an image of the 0 to 6 km shear values at 7 pm.

As the evening progressed a Tornado watch was issued with the designation of PDS or Particulary Dangerous Situation, indicating a high potential for strong and long lived tornadoes. Although data is still being gathered, preliminary data suggests significant tornado damage from a storm that moved out of Alabama into Dade, Walker, and especially Catoosa county Wednesday evening. Other tornado tracks were across Floyd and Bartow counties as well as Meriwether through Spaulding and damage from Harris, Lamar and Monroe counties.In total, 14 tornadoes tracked across the Peachtree City forecast area, which includes most of north and central Georgia. Another tornado tracked through Rabun County (Greenville-Spartanburg Forecast Office), which would bring the total number of tornadoes across north and central Georgia to 15. It should be stressed that this is all preliminary data and more counties will be included in damage summary updates to be refined later today. More detailed preliminary information can be found in the Local Storm Reports.

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This is an image of the tracks of all the storm rotations for April 27-28th. You can mouse-over and click on the image for a larger view.

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This is an image of the tracks of tornadoes on April 27-28th. Click on the image for a larger view.

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This is a time-lapse snapshot of the supercell the hit Tuscaloosa and Birmingham. This cell lasted more than 8 hours and traveled over 380 miles. Click on the image for a larger view and more information.