Jonathan Erdman
The April 25-28, 2011, Super Outbreak remains one of the worst tornado outbreaks in United States history.
This single outbreak claimed over 300 lives, injured 2,775 and was responsible for $12 billion in total damage, making it the costliest tornado outbreak in U.S. history.
Ten years later, there are jaw-dropping facets of this massive outbreak that remain burned in the memory of the meteorologists and journalists on our team – here's a list of them.
1. A Swarm of Tornadoes
An incredible 349 tornadoes were spawned in just over 72 hours April 25-28, 2011, according to NOAA.
While the Deep South – Alabama, Mississippi, Georgia and Tennessee – bore the brunt of it, tornadoes tore through parts of 21 states from Texas to central New York.
According to the Iowa Environmental Mesonet, 929 tornado warnings were issued by 44 different National Weather Service offices from April 25 through 28.
Map of tornado tracks from the April 25-28, 2011, Super Outbreak, color-coded by intensity (EF0: aqua; EF1: light green; EF2: yellow; EF3: orange; EF4: red; EF5: pink). Notes: 1) Tornadoes are rated based on the worst damage along its track, which is almost always not representative of all the damage along its path. 2) These are general tracks.2. Almost 200 in One Day
Officially, 199 tornadoes in 15 states were tallied on April 27, 2011, a record for any calendar day in the U.S. This topped the number of tornadoes witnessed on April 3, 1974 (148), considered the other Super Outbreak.
That's basically an entire April's worth of tornadoes in one day; April averaged 194 tornadoes over a 20-year period from 2000 through 2019.
The NWS-Huntsville, Alabama, office issued 92 tornado warnings that day. A pair of additional tornado warnings for the NWS-Huntsville area of responsibility were issued by the NWS office in Jackson, Mississippi, while Huntsville employees themselves took shelter.
Tornado tracks, Enhanced Fujita scale ratings and county fatalities on Apr. 27, 2011. Note: The final Apr. 27 tornado count differs from that shown in map above.3. Tornado Paths Total Thousands of Miles
The individual tornado paths from the April 25-28, 2011, Super Outbreak added up to an almost unfathomable 3,200 miles, by far the most of any U.S. outbreak, according to Greg Forbes, the former severe weather expert at The Weather Channel.
This total path was over 600 miles longer than the April 3-4, 1974, Super Outbreak.
If one could place these tornado paths end to end, it would be roughly equal to the driving distance from Portland, Maine, to San Francisco.
Infrared satellite loop from April 27-28, 2011, showing the tornado outbreak across the South and East.4. Deadliest Since the Great Depression
This siege of tornadoes claimed 324 lives, 319 of those on April 27, the deadliest day of tornadoes in the U.S. since March 21, 1932, according to the definitive April 27 outbreak study from Knupp, et al.
Of the 199 tornadoes on April 27, 15 were rated violent tornadoes, either EF4 or EF5 on the Enhanced Fujita scale. The Centers for Disease Control and the Red Cross found 89.5 percent of the deaths in this outbreak were from these violent tornadoes.
According to the NWS, the average path length of the 15 violent tornadoes was 66 miles. The Hackleburg/Phil Campbell, Alabama, EF5 tornado was on the ground for 132 miles.
Adding to the danger, these storms moved fast – generally from 45 to 70 mph – which left much less time to take action.
Tracks of 15 violent - EF4 or EF5 - tornadoes on April 27, 2011.5. Off-the-Chart Parameters
The combination of instability – warm, humid air near the surface overlaid by cold, dry air aloft – and wind shear in the atmosphere, particularly at low levels crucial for the spawning of tornadoes, was quite simply in another realm on April 27, 2011.
Meteorologist and researcher Jon Davies blogged about the rarity of seeing such extreme values of shear and unstable air. Typically, any high values of one are at least somewhat tempered by lower values of another. Not on April 27.
"I've looked through my own databases of tornado cases over the past decade, and can't find any tornado environment that even approaches this one," Davies wrote.
The significant tornado parameter (STP) uses a combination of both wind shear and instability in the atmosphere's lowest levels to diagnose the tornado risk. A value of 1 is considered an environment capable of at least F/EF2 tornadoes.
On April 27, STP values reached values from 10-12 in eastern Mississippi and Alabama in the afternoon (see Fig. 2 in the definitive April 27 outbreak BAMS paper from Knupp, et al.)
It's no wonder there were so many long-track, violent tornadoes.
0-3 km significant tornado parameter (STP) at 10 p.m. EDT on April 27, 2011. Values of this parameter were virtually off the chart, compared to a more typical severe weather scenario.6. Three Separate Rounds of Tornadoes in One Day
It not uncommon for a morning cluster of severe thunderstorms to be followed by a more dangerous round of afternoon supercells. The morning thunderstorm cluster typically produces damaging winds, flooding rain and perhaps a few tornadoes.
An early-morning squall line in the Tennessee Valley on April 27, 2011, produced an incredible 76 tornadoes in Mississippi, Alabama, east Tennessee, and north Georgia, according to the Knupp et al. 2014 paper. This included some long-track EF3 tornadoes, an intensity somewhat rare for early-morning squall lines.
That would be an impressive outbreak alone.
Just hours later, a second line of thunderstorms in the late-morning hours spawned another seven mainly weak EF0 or EF1 tornadoes in northern Alabama.
Finally, the most destructive and deadly supercells roared across Mississippi, Alabama, north Georgia, east Tennessee and far southwest Virginia that afternoon and evening.
Radar loop from 7:01 a.m. to 11:03 p.m. CT, April 27, 2011, illustrating the three rounds of severe t-storms in the Deep South and Tennessee Valley.7. The Town Hit Twice
Because of these three rounds of severe thunderstorms, some locations were hit multiple times on April 27.
Cordova, Alabama, northwest of Birmingham, was just one unfortunate example.
Around 5:20 a.m. CDT, a tornado intensified quickly as it tracked into the city of just over 2,000 residents. Damage there was rated EF3 on the Enhanced Fujita scale.
Less than 12 hours later, another long-track tornado approached the city. After weakening west of town, the tornado strengthened quickly as it moved into Cordova, carving a half-mile-wide path of damage rated EF3 in the downtown area.
Incredibly, Marshall County, Alabama, was affected 15 separate times by a tornado on April 27, 2011.
Aerial photo of Long Memorial United Methodist Church in Cordova, Alabama, after a pair of tornadoes tore through the town on April 27, 2011.8. Watching the Tuscaloosa Tornado Live
Perhaps the most indelible live coverage of this Super Outbreak was the split-screen shown on ABC 33/40 in Birmingham, Alabama, showing both a live-cam shot of a wedge tornado roaring through Tuscaloosa, Alabama, as meteorologist James Spann was showing the classic hook echo and debris ball (indicating tornado-lofted debris) on radar.
In roughly 90 minutes, the EF4 tornado claimed 65 lives along an 80-mile path from Greene County, Alabama, through Tuscaloosa into the northern suburbs of Birmingham.
Despite the deadly toll, we'll never truly know how many lives were saved by timely NWS warnings, and the considerable effort of the media to communicate those warnings.
A clip from an ABC 33/40 broadcast on April 27, 2011, showed a live cam of a large tornado tearing through Tuscaloosa, Alabama (lower left), while meteorologist James Spann showed the tornado on radar (upper right). This clip was shown during an episode of Weather Geeks on The Weather Channel.9. A Supercell's Long Journey
The term supercell refers to a rotating thunderstorm that is persistent, on a time scale much longer than a single, ordinary thunderstorm you may see, for instance, in the summer over the Southeast.
The Knupp et al. study documented three prolific long-track supercells on April 27.
One supercell tracked over 500 miles in nine hours and spawned the Cordova, Alabama, afternoon tornado mentioned earlier.
The parent supercell that spawned the Tuscaloosa and west Birmingham EF4 tornadoes was tracked on radar for over seven hours from its formation in Newton County, Mississippi, to Macon County, North Carolina, after which it finally fizzled. One supercell, 450 miles, four states.
Radar composite from 3:40 p.m. to 11:40 p.m. EDT of the supercell responsible for the Tuscaloosa and west Birmingham tornadoes on Apr. 27, 2011.Now, let's cover the mind-boggling damage left in the wake of these intense tornadoes.
10. Tornado Plows a Field
The first of four EF5 tornadoes on April 27, 2011, raked through east-central Mississippi, leaving some incredible damage in its wake.
Northeast of Philadelphia, Mississippi, a swath of ground was scoured out to a depth of two feet, in some places. The tornado even ripped sections of asphalt from a road.
(MORE: NWS Summary, With Photos)
11. Mobile Home Thrown 300 Yards, Obliterated
The same EF5 tornado that scoured the ground near Philadelphia, Mississippi, claimed its three lives in an unfathomable way.
The NWS-Jackson, Mississippi, storm survey report tells the story.
The three fatalities occurred in northwest Kemper County when a strapped down doublewide mobile home was thrown a distance of approximately 300 yards into a treeline, and then obliterated with the debris and framing scattered many hundreds of yards down the path. There was no indication of ground impacts between the original site of the mobile home and where it ended up to indicate that the mobile home bounced extensively as it traveled.
12. Appliances Shredded or Missing
One of the four EF5 tornadoes on April 27, raked through Smithville, Mississippi, with peak winds estimated at 205 mph.
These NWS survey results speak for themselves:
-Appliances and plumbing fixtures were found shredded or missing.
-A home's concrete slab was pulled out of the ground, with a large part missing in the center.
-An SUV was tossed a half-mile into the town's water tower, then blown another quarter-mile.
-Another pickup truck parked in front of a destroyed home hadn't been found.
April 27, 2011, was the only day on record with two F/EF5 tornadoes in Mississippi. They were the first 5-rated tornadoes there since March 3, 1966.
The remains of a Ford Explorer in Smithville, Mississippi, after an April 27, 2011, tornado.13. One 'Powerful' Outbreak
The Tennessee Valley Authority's electrical generation and distribution took a massive hit from the 2011 Super Outbreak.
Over 300 transmission towers were mangled on April 27. Two power plants were forced to shut down, including the TVA's Browns Ferry Nuclear Power Plant near Decatur, Alabama.
Power outages lasted for days in Huntsville, Alabama, affecting everything from gas stations to traffic signals.
The Knupp et al. study concluded power outages caused by the morning pair of squall lines, including non-functioning outdoor sirens and NOAA weather radio transmitter outages, reduced the ability to get warnings out to the public during the deadliest afternoon and evening supercells in central and northern Alabama.
These power lines west of Huntsville, Alabama, were destroyed by an EF5 tornado on April 27, 2011.14. Radar That 'Oversampled' a Tornado
Doppler radar led the way to improved severe weather nowcasting, including increasing lead times for tornadoes. On April 27, a Doppler radar succumbed to a massive tornado.
WAFF-TV in Huntsville, Alabama, was showing live Doppler radar and cam shots of the massive EF5 tornado that earlier devastated the towns Phil Campbell and Hackleburg.
The radar was directly in the path of this wedge tornado as it tracked into Limestone County. Both the radar and radome encasing the radar were blown off and destroyed, leaving just the tower standing.
The radar was replaced later in 2011 and the church reopened in a new location.
The radome and radar from WAFF-TV was ripped from its tower, and the nearby Bethel Church of Christ was destroyed on Apr. 27, 2011.15. Debris 220 Miles Away
A comprehensive study of lofted tornado debris in 2012 from the April 2011 Super Outbreak was the first such study to utilize social media.
A team led by John Knox at the University of Georgia pored through hundreds of pictures of debris transported downstream by the outbreak's massive tornadoes to map out start and end points of individual pieces of debris.
A photograph from Phil Campbell, Alabama, leveled by an EF5 tornado, landed in Lenoir City, Tennessee, some 220 miles away.
A photograph from Phil Campbell, Alabama, leveled by an EF5 tornado on April 27, 2011, was later found in Lenoir City, Tennessee, some 220 miles away.It's quite common for violent (EF4 or EF5) tornadoes to transport debris tens of miles downstream, mainly paper such as canceled checks and photos.
A jacket from Hackleburg, Alabama, was found 68 miles away.
16. A Monthly Tornado Record
The Super Outbreak and several other tornado outbreaks pushed April 2011's U.S. tornado count to a monthly record of 758, smashing the previous record in any month from May 2003 (542) by over 200 tornadoes.
This was almost four times the April average (194), and also greater than the combined average of the three most active months, April through June (671).
April U.S. tornado counts from 2011 through 2019. The 20-year average U.S. tornado total from 1999-2018 (189 tornadoes) is shown by the horizontal thin white line.The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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