2011 Super Outbreak

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Approximate touchdown location of tornadoes from April 25–28, 2011, with violent EF4+ tornadoes highlighted
Interactive map

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• Tornadoes on April 25
• Tornadoes on April 26
• Tornadoes on April 27 (EF0–EF3)
• Tornadoes on April 28
• EF4 tornadoes on April 27
• EF5 tornadoes on April 27

The outbreak was caused by a vigorous upper-level trough that moved into the Southern Plains states on April 25. An extratropical cyclone developed ahead of this upper-level trough between northeastern Oklahoma and western Missouri, and moved northeastward. ^[20] Conditions were similar on April 26, with a predicted likelihood of severe thunderstorms, including an extended threat of strong to violent long-track tornadoes throughout the afternoon and evening hours; mixed-layer CAPE values were forecast to be around 3000–4000 J/kg, around east Texas, Louisiana, and Arkansas. The storm mode on April 26 was predicted to include mostly discrete tornadic supercells during both the afternoon and the early evening, shifting over to a mesoscale convective complex, with more of a threat of damaging winds and hail during the nighttime hours. ^[21]

As the storm system moved eastward toward the Ohio, Mississippi, and Tennessee Valleys on April 27, a very powerful 80–100 knot mid-level jet stream moved into the Ohio and Tennessee Valleys behind the trough and created strong wind shear, along with a low pressure center moving quickly northeastward across those areas on April 27. During the afternoon of April 27, CAPE values were estimated to be in the range of 2000–3000 J/kg across Louisiana and southern Mississippi, with the moderate instability moving northeastward across the southern Tennessee Valley; additionally, temperatures across the southeastern United States ranged from the 70s °F (mid-20s °C) to the lower 90s °F (near 35 °C). Helicity levels ranged from 450 to 600 m²/s², which supported some significant tornadic activity and strong to violent long-track tornadoes. ^[22]

A total of 56 severe weather watches were issued by the Storm Prediction Center (SPC) over those four days in the outbreak area. This included 41 tornado watches—10 of which were particularly dangerous situation (PDS) watches—and 15 severe thunderstorm watches. ^{[23] [24]} The SPC assigns numbers to each severe weather watch issued starting at the beginning of each year; the organization unsuccessfully used two of their allocated watch numbers during this outbreak (numbers 208 and 209). ^[25]

April 25

A large area of possible severe storms for April 25–27 was forecast as the Storm Prediction Center (SPC) issued a moderate risk of severe weather for three consecutive days, centered over Arkansas through Tennessee. At 3:25 p.m. CDT (20:25 UTC), the SPC issued a particularly dangerous situation (PDS) tornado watch for much of Arkansas and parts of Missouri, Oklahoma, Texas, and Louisiana. ^[26] By the evening hours of April 25, tornadoes had been reported across a few states, some of which caused significant damage in Arkansas. An intense supercell thunderstorm tracked near the Little Rock area and a tornado emergency was declared for the city of Vilonia. A large EF2 wedge tornado struck the town, subsequently causing severe damage and killing four people. ^{[27] [28]} A strong EF3 tornado had also struck the Hot Springs Village area earlier that evening; that tornado caused severe damage and resulted in one death. Later that evening, another EF2 tornado caused extensive damage to both a school building and Little Rock Air Force Base as well. ^[29] Severe flooding continued across a large area from the Red River valley to the Great Lakes. ^[30] A total of 42 tornadoes and five tornado-related deaths were confirmed on the 25th.

April 26

This animation of satellite images from April 26 through the morning of April 28 shows the development of the storm system which spawned the tornadoes.

A high risk of severe weather was issued for April 26 for portions of Louisiana, Arkansas, Oklahoma, and Texas along and near the Interstate 30 corridor as conditions became even more favorable for extreme weather. ^[31] A large PDS tornado watch with very high possibilities for tornadoes was issued for that same area that afternoon. ^[32] Widespread tornado warnings were then issued in that area later that evening. ^{[33] [34] [35]}

An upper-level negatively-tilted trough with two embedded shortwaves generated two surface lows that propagated generally east. One of the surface lows tracked northeast along the Mississippi River into Wisconsin as it occluded. Tornado watches were issued for the Lower Great Lakes during the afternoon hours as supercell thunderstorms developed along the warm front lifting north across central Michigan. Two tornadoes touched down in Michigan and caused damage to farm structures. Further east, severe thunderstorms caused scattered wind damage and large hail across Pennsylvania and New York. Two-inch-diameter hail was reported in Lock Haven, Pennsylvania. ^[36] An isolated supercell moved across Central New York throughout much of the afternoon, producing golf ball-sized hail in Syracuse and spawning a very brief EF1 tornado in Verona Mills, which primarily caused damage to trees. Another tornado — this one being in Gilbertsville — caused significant damage to a school's athletic field. ^[37]

The second surface low corresponded to an area of strong upper level divergence ahead of the downstream shortwave. As the low formed across Texas and deepened while moving east, a tightening pressure gradient force further strengthened the low-level jet, therefore creating a broad warm sector across the southeastern states. This also generated stronger wind shear, providing better organization for the supercell storms as a result. Numerous tornadoes touched down across several states, including Texas, Louisiana, and Arkansas. Most of those tornadoes were weak, but a few of them caused considerable damage. A long-tracked wedge tornado caused EF2 damage in rural portions of Texas and Louisiana. ^[38] An EF3 tornado destroyed structures and caused severe damage at Fort Campbell, Kentucky, as well. ^[39] A total of 55 tornadoes were confirmed on the 26th, although no fatalities occurred.

April 27

The Storm Prediction Center (SPC)'s forecast for April 27, with a high risk area within the Southern U.S.

Significant severe weather was ongoing early on April 27 (in the overnight hours) and continued for the entire calendar day virtually unbroken. For the second day in a row, the SPC issued a high risk of severe weather for the Southern United States. Later that morning, the SPC even increased the probability for tornadoes to 45 percent along a corridor from Meridian, Mississippi, to Huntsville, Alabama, an extremely rare issuance exceeding the high risk standards. Conditions became increasingly favorable for tornadoes during such an extreme tornado outbreak. ^[40]

Morning squall lines

During the early morning hours, a cold front with several embedded low pressure areas extended from east Texas northeastward into the Ohio River Valley. An upper-level disturbance that had moved across the frontal boundary the previous evening sparked an area of thunderstorms that morphed into a squall line. This line of severe thunderstorms would produce tornadic activity from the evening on April 26 into the late morning of April 27. Early in the morning the squall line, packing straight-line winds and numerous embedded tornadoes, moved through Louisiana and Mississippi before proceeding to affect North and Central Alabama and parts of Middle and East Tennessee. The line strengthened as it moved through Alabama, partially due to a high amount of low-level moisture from the Gulf of Mexico and increasing wind shear. ^[41]

A majority of the tornadoes embedded in this initial squall line were weak, though several were strong and as such caused significant damage. An EF3 tornado caused major damage to homes in Coaling, Alabama, an EF2 and an EF3 tornado produced severe damage and a fatality near Eupora, Mississippi. Another EF3 tornado resulted in heavy damage in downtown Cordova, Alabama, which was struck by a violent EF4 tornado later that afternoon. An EF2 also struck Cahaba Heights near Birmingham. One embedded cell began producing tornadoes just after 5:00 a.m. CDT (10:00 UTC), starting with an EF1 tornado striking Berry, Alabama. This was soon followed by the Cordova EF3 tornado. ^[42] As the line entered Cullman County, Alabama, the cell, a mesoscale convective vortex (MCV), began exhibiting a comma head appearance and produced another long-tracked EF2 tornado that struck the town of Hanceville, killing one person. The MCV would then produce 13 tornadoes (most rated EF1) to the northeast in Marshall County, many of which occurred simultaneously. Two more tornadoes were produced as the comma head-shaped embedded cell continued northeast along the Jackson/DeKalb county line, including a long-track EF1 that resulted in a fatality near Pisgah. The same area was impacted later that day by a high-end EF4 tornado. ^[41] Another EF1 tornado occurred in Dade County, Georgia, with the cell, and six more tornadoes struck Hamilton County, Tennessee, five of which were in the Chattanooga area. The 26th and final tornado produced by the MCV was an EF2 tornado in northern Bradley County, Tennessee, which hit at 9:45 a.m. EDT (13:45 UTC). ^[43] The initial storms caused widespread power and telephone line outages across Alabama and Tennessee. This line of storms also caused some NOAA weather radio transmitter sites to stop functioning for the remainder of the outbreak. Because of this, more than one million customers were without power and had no warning of any approaching tornadoes later that day. ^[41]

From the late morning to the early afternoon, another squall line moved through northern parts of Mississippi and Alabama as high wind shear and low-level moisture persisted. However, this time several discrete supercells developed along and in front of the line, spawning seven weak tornadoes across Morgan, Limestone, and Madison Counties in northern Alabama around noon that day. ^[41]

Afternoon supercells

Extremely deep ground scouring near Philadelphia, Mississippi, caused by a fast-moving EF5 tornado that killed three people.

The most intense supercells of the outbreak developed around midday in central Mississippi and began tracking eastward. With the extreme instability and wind shear, they quickly intensified and eventually became tornadic, shortly thereafter resulting in strong to violent tornadoes. Responding to the high risk issued by the SPC and the already unstable atmosphere expected to become even more unstable throughout the afternoon hours, a PDS tornado watch was issued at 1:45 p.m. CDT (18:45 UTC) for much of Alabama and portions of Mississippi, Tennessee, and Georgia. A widespread complex of supercell storms overspread the states of Mississippi and Alabama and violent tornadoes began rapidly touching down as the afternoon progressed. ^[41]

By mid-afternoon, as wind shear and low-level moisture continued to dramatically increase, a tornado emergency was declared for Neshoba County, Mississippi, as a large tornado was reported on the ground by both storm spotters and a camera atop a television tower from ABC affiliate WTOK-TV (channel 11) in Meridian, Mississippi. This powerful EF5 tornado caused incredible damage northeast of Philadelphia, Mississippi, where pavement was torn off from roads, vehicles were thrown, and the ground was scoured out to a depth of 2 feet (0.61 m) by the tornado. Three people died when a mobile home was thrown 300 yards (270 m) into a wooded area, obliterating it in the process. ^[44] Another very long-tracked EF4 tornado passed near the town of Enterprise, Mississippi, killing seven people before crossing into Alabama and eventually dissipating. Four tornadoes were officially rated EF5 on the Enhanced Fujita scale that day. One of those EF5 tornadoes struck the town of Smithville, Mississippi, where many well-built brick homes were reduced to bare slabs, numerous hardwood trees were completely debarked, and an SUV was hurled half a mile into the top of the town's water tower, subsequently leaving behind a visible dent. Another long-tracked EF5 wedge tornado passed through rural portions of Alabama and Tennessee, becoming the deadliest tornado of the outbreak as it completely devastated the towns of Hackleburg, Phil Campbell, Mount Hope, Tanner, and Harvest, killing 72 people. This marks only the second day in history (after April 3, 1974) that there were more than two F5/EF5 tornadoes reported. ^[45]

The tornadoes continued tracking through central Alabama that afternoon and into the early evening hours. A dangerous and destructive tornado struck the city of Cullman, Alabama, at around 3:00 p.m. CDT (20:00 UTC). This large, multiple-vortex tornado was captured on several tower cameras from television stations, such as Fox affiliate WBRC (channel 6) and ABC affiliate WBMA-LD/WCFT-TV/WJSU-TV (channels 58, 33, and 40) both out of Birmingham. The tornado caused extensive destruction in the city's downtown area; it was ultimately rated EF4. The final damage count was 867 residences and 94 businesses in Cullman; six people died as well. ^[46] The town of Cordova, Alabama, which had already been damaged by an EF3 tornado from the initial round of storms, was struck by an EF4 tornado that killed 13 people. Two violent EF4 tornadoes also ripped through Jackson County, Alabama, one of which caused a fatality near Bridgeport while the other passed near Pisgah and into Georgia where it caused major damage in Trenton and killed 14 people. At around 5:10 p.m. CDT (22:10 UTC), a very large and exceptionally destructive tornado struck Tuscaloosa, Alabama, and about 40 minutes later, that same tornado struck the northern suburbs of nearby Birmingham. ^[47] A tornado emergency was issued for both cities, along with many other cities that day. Many local television stations, including WBRC and WBMA-LD/WCFT/WJSU, as well as CBS affiliate WIAT (channel 42), broadcast live footage of this long-tracked tornado in both Tuscaloosa and Birmingham. A debris ball was observed by the Birmingham NEXRAD, indicating that the tornado was causing extreme damage. ^[48] This tornado killed 64 people and caused extensive devastation in densely populated areas, and the tornado struck several of the same small communities as the April 1956 F4, the April 1977 F5 and the April 1998 F5 tornadoes that hit portions of the Birmingham area. The supercell that produced the Tuscaloosa/Birmingham EF4 tornado originated in Newton County, Mississippi. The same supercell produced another EF4 tornado later that evening that killed 22 people and struck the Ohatchee, Alabama, area and eventually crossed into Georgia, causing additional damage near Cave Spring before dissipating. Further to the south, a mile-wide EF3 tornado killed 7 people in mostly rural areas and caused major damage in the small town of Eoline. The final EF5 tornado of the day caused remarkable damage in and around the town of Rainsville, Alabama, killing 25 people before crossing into Georgia and dissipating. Tornadoes continued touching down further to the northeast as the sun set, particularly in Georgia. This included a long-tracked EF4 tornado that caused major damage in Ringgold, Georgia, Apison, Tennessee, and Cleveland, Tennessee, killing 20 people along the path. After dark, violent tornadoes continued to touch down, and a nighttime EF4 tornado destroyed many lakeside homes at Lake Martin in eastern Alabama, killing seven people. Additional strong nighttime tornadoes occurred in Georgia, including an EF3 that killed two people in Barnesville, and another EF3 that destroyed homes and killed one person at Lake Burton. ^{[42] [49]}

Continued activity farther east

Powerful tornadoes touched down across Tennessee as well that evening. A violent EF4 struck the community of New Harmony, Tennessee, where homes were leveled, vehicles were tossed, and four people were killed. ^[50] Two EF3 tornadoes crossed paths in Greene and Washington counties (coming a couple hours apart), resulting in eight fatalities. The rural communities of Horse Creek and Camp Creek suffered major damage from those tornadoes late that evening. ^{[51] [52]} A very large EF4 wedge tornado leveled a mile-wide swath of forest through 14 miles (23 km) of Great Smoky Mountains National Park, resulting in many trails being closed. ^{[53] [54]} At Chilhowee Lake, large metal power line truss towers were torn and thrown from their concrete supports that they were anchored to. ^[55]

A secondary area of severe weather also developed that afternoon and evening along a corridor extending from central and northern Virginia northward through Maryland, Pennsylvania, and New York, continuing into early April 28. Many tornadoes touched down in this area as well. ^{[56] [57]} Most of these tornadoes were weak, though an EF2 tornado touched down near the town of Halifax, Virginia, and caused severe damage to homes in the area, resulting in one death. ^[58] Tornado alerts were issued for Southern Ontario as far north as Ottawa as well; one tornado was later confirmed in Fergus, Ontario. ^[59]

Overview

SPC Storm Reports for April 27

A statewide review by emergency management officials recorded 249 fatalities in Alabama as of the morning of April 30, 23 of which were not tornado-related. ^[11] Eventually, a total of 238 tornado-related deaths would be confirmed in the state. Damage and power outages in the Huntsville area were so widespread that at one point over 650,000 people were out of power in the Tennessee Valley Authority system. The EF5 tornado that struck Hackleburg and Phil Campbell damaged main high-transmission power lines coming from Browns Ferry Nuclear Plant near Tanner. These towers were the main supply of electrical power to much of North Alabama, and some were without power for two weeks. The tornado just missed the Limestone Correctional Facility, which less than a year later would be struck by another tornado. ^{[60] [61]}

The Storm Prediction Center received 292 reports of tornadoes in the preceding 24 hours. ^[17] In addition to setting the record for most tornadoes in a calendar day (223; midnight to midnight CDT (05:00 – 05:00 UTC)), it also broke the record for the most tornado touchdowns in any 24-hour period with 226 from 12:40 a.m. to 12:40 a.m. CDT (05:40 – 05:40 UTC) April 27–28, breaking the old 24-hour record of 148 set by the 1974 Super Outbreak. Of those 226 tornadoes, 59 touched down in Alabama and 83 began in Tennessee, accounting for 62.8 percent of the tornadoes that touched down on April 27. ^[62] On April 27 alone, the National Weather Service in Huntsville, Alabama, issued 92 tornado warnings, 31 severe thunderstorm warnings, and seven flash flood warnings. ^[63]

April 28

Tornado watches were issued for the Atlantic coast from Pennsylvania to Florida at the start of the day and continued through the morning and early afternoon, but tornadoes were forecasted to generally be weaker and more isolated. ^[64] Despite this, the secondary portion of the outbreak that had begun producing scattered tornadoes throughout the Mid-Atlantic and East Coast regions the previous evening intensified during the early hours of the morning, producing numerous tornadoes. A particularly active region, in which there were some strong tornadoes, ^[65] was the Interstate 81 corridor extending from southwest Virginia, ^[66] northward through the Shenandoah Valley ^[67] and into Pennsylvania, ^[68] and New York. This included the deadly EF3 tornado that struck the town of Glade Spring, Virginia, very early in the morning, where three people died. ^[69] Tornadoes were also reported in Florida, ^[70] Georgia, South Carolina, ^[71] North Carolina, ^[72] and Maryland. Most of these tornadoes were weak. Although tornado watches were issued, no tornadoes were spotted in New Jersey ^[73] or Washington, D.C. ^[66] In the wake of the tornadoes and severe thunderstorms, widespread flooding hit the Midwest, South, and Eastern Seaboard, with extensive flood and flash flood warnings issued. ^[74] The last tornadoes of the outbreak touched down that afternoon in eastern North Carolina, which was hard hit in the April 16 outbreak, though the tornadoes that impacted the area this time around were weak. ^[75] The system moved out into the Atlantic Ocean that evening, with the exception of isolated thunderstorms over central Florida that night into April 29, although no more tornadoes were produced. ^[76]

Confirmed tornadoes

See also: List of tornadoes in the 2011 Super Outbreak

2011 Super Outbreak

The storm system responsible for the historic tornado outbreak across the Southern United States on April 27

Daily statistics ^[77]

Date	Total	EF0	EF1	EF2	EF3	EF4	EF5	Deaths	Injuries
April 25	42	17	20	4	1	0	0	5	59
April 26	55	31	19	4	1	0	0	0	4
April 27	223	72*	81	36	19	11	4	316	2,986+
April 28	47	18	23	5	1	0	0	3	51
Total	367	138*	143	49	22	11	4	324	3,100+

* One tornado touched down in Ontario, Canada, on April 27 and was rated as an F0. It is counted as an EF0 in this table.

A record 367 tornadoes touched down over the span of four days, 37 of which were EF3+ tornadoes. Four tornadoes were rated EF5 – behind only the 1974 Super Outbreak (7 F5s). Several of the strong to violent tornadoes that formed were exceptionally long-tracked, with six tornadoes on April 27 tracking over 60 miles (97 km). Many tornadoes on the afternoon of April 27 were spawned from a collection of supercells that moved across Mississippi, Alabama, Tennessee, and Georgia.

Vilonia, Arkansas

1⁄2-mile (0.80 km). ^{[88] [89]} The tornado killed three people, injured eight others, and caused $1.1 million in damage across its path. ^{[89] [90]}

The supercell thunderstorm that produced this tornado formed around 1:00 p.m. CDT south of Jackson, Mississippi. ^[91] Traveling briskly to the northeast, it warranted a severe thunderstorm warning within 25 minutes and was deemed potentially tornadic by 1:36 p.m. CDT. ^{[91] [92]} A tornado finally touched down at 2:30 p.m. CDT just east of the Philadelphia Municipal Airport. It quickly intensified and began producing EF5 damage by 2:38 p.m. CDT; extreme ground scouring, up to 2 feet (0.61 m) deep in places, occurred in northeastern Neshoba County. After crossing into Kemper County, the tornado obliterated a mobile home, killing all three inside. ^[89] It reached EF5 strength a second time near the Kemper–Winston county line where extreme ground scouring again took place and pavement was scoured. ^{[89] [91]} Extreme tree damage took place along the track and it ultimately dissipated at 3:00 p.m. CDT about 6 miles (9.7 km) north of Mashulaville. ^[89]

This was the first tornado to cause F5/EF5 damage in Mississippi since the Candlestick Park tornado on March 3, 1966. Additionally, the formation of the Smithville tornado later that day marked the first time since statistics have been kept that two EF5 tornadoes have been recorded in Mississippi on the same day. Prior to this, the last confirmed EF5 tornado was the Parkersburg, Iowa tornado on May 25, 2008. ^[89]

Cullman/Arab, Alabama

Main article: 2011 Cullman–Arab tornado

Vilonia, Arkansas

Cullman/Arab, Alabama

Outbreak death toll

State/Province	Fatalities
Alabama	238
Arkansas	5
Georgia	14
Mississippi	31
Tennessee	32
Virginia	4
Totals	324
Only tornado-related deaths are included (24 deaths were not caused by tornadoes)

Alabama Governor Robert J. Bentley declared a state of emergency in the state of Alabama on April 27, due to storm damage from severe thunderstorms earlier that day as well as forthcoming severe weather later that day. States of emergency were also declared in Arkansas, Kentucky, Mississippi, Missouri, Tennessee, and Oklahoma because of the flooding and tornadoes. ^[176] Following the tornado outbreak on the evening of April 27, President Barack Obama granted a federal emergency declaration for the state of Alabama, giving federal assistance, including search and rescue assets, to the affected region. ^[177]

More than 2,000 National Guard troops were deployed to Alabama, assisting local and state first responders in search and rescue efforts. ^[178] President Obama visited the affected areas of Alabama on April 29. ^[179] Also on April 29, he approved a federal disaster declaration for seven Mississippi counties: Clarke, Greene, Hinds, Jasper, Kemper, Lafayette, and Monroe. ^[180]

Electricity outage

Storms through the area severely damaged Tennessee Valley Authority (TVA)'s power grid for transmitting electricity throughout the region. More than 300 power transmission towers, 120 to 150 feet (37 to 46 m) tall, were destroyed in the storms, some "twisted like bow ties" according to National Weather Service meteorologist Eric Holweg. The towers supported some 90 transmission lines, a mixture of 500kV and 161kV lines. Those lines provided power from TVA to 128 regional distributors. ^{[181] [182]}

Transmission tower bent near Huntsville, Alabama.

TVA lost the ability to transmit power from both Browns Ferry Nuclear Power Plant and Widows Creek Fossil Plant after the storms on April 27, requiring both to be shut down. The nuclear plant's cold shutdown was supported by diesel generators for four days until a second 161kV line could be restored to the plant. The loss of redundant off-site power required a "notification of unusual event", the lowest of four levels of concern dictated by the NRC. Some 60 percent of the sirens for warning residents of worse problems around Browns Ferry were disabled by the storms, and the plant had to arrange plans to use cars with loudspeakers to warn residents in case of another problem. ^{[99] [182]} The Nuclear Regulatory Commission stated at a press conference: "The plants' conditions are stable and are being placed in a cooled-down condition." ^{[183] [184]}

Huntsville was the largest city with no electricity from TVA. ^[182] All the traffic lights were off, a dusk-to-dawn curfew was imposed, students were sent home from United States Space Camp, and the Panoply Arts Festival was canceled. ^{[185] [186] [187]} Power was restored gradually to Huntsville, beginning with 3 percent on the morning of May 1. ^[188] Only localized outages remained eight days after the storm. ^[189] In addition to traffic and safety issues, the outage caused difficulties with water treatment and distribution and retail of all kinds, including gasoline and food purchases. ^{[188] [190]}

Ontario electricity outages were minor, mostly caused by the windstorms of April 28. Although they affected thousands of people at different times throughout the day, all power was restored by the end of the day. ^{[171] [172] [173] [174] [175]}

See also

• Tornadoes portal
• Weather portal
• United States portal

• Tornadoes of 2011
• List of North American tornadoes and tornado outbreaks
• List of F5 and EF5 tornadoes
• List of F4 and EF4 tornadoes
  • List of F4 and EF4 tornadoes (2010–2019)
• List of disasters in the United States by death toll
• Tornado records
• Tri-State Tornado – Deadliest tornado in North America, and made March 18, 1925, the deadliest tornado day recorded in United States.
• 1932 Deep South tornado outbreak – Deadliest tornado outbreak in Alabama history, including an F4 tornado that tracked through Tuscaloosa.
• 1936 Tupelo–Gainesville tornado outbreak – Infamous tornado outbreak occurring on April 5–6, 1936. Deadliest U.S. tornado outbreak since the March 1925 (Tri-State Tornado) outbreak, thus surpassing the March 1932, April 1974, and April 2011 outbreaks in total fatalities.
• April 1956 Birmingham tornado – F4 tornado that hit the northern Birmingham suburbs on April 15, 1956.
• 1974 Super Outbreak – Infamous tornado outbreak that occurred on April 3–4, 1974, similar in severity to the 2011 Super Outbreak; though the 2011 event surpassed the 1974 Super Outbreak as the largest recorded outbreak.
• Tornado outbreak of April 25–28, 2024, a devastating tornado outbreak that occurred exactly 13 years later
• April 1977 Birmingham tornado – F5 tornado that hit the northern Birmingham suburbs on April 4, 1977.
• 1994 Palm Sunday tornado outbreak – March 27, 1994, outbreak that produced an F4 tornado in St. Clair, Calhoun and Cherokee Counties in north-central Alabama.
• April 1998 Birmingham tornado – F5 tornado that struck western parts of Birmingham on April 8, 1998.
• December 2000 Tuscaloosa tornado – F4 tornado that hit southeast suburbs of Tuscaloosa on December 16, 2000.

Notes

1. The 170 miles per hour (270 km/h) wind speed is based on the finalized information published by the NOAA National Climatic Data Center (NCDC), which is now maintained by the NOAA National Centers for Environmental Information (NCEI) as well as a web page made by the National Weather Service (NWS) Birmingham, Alabama. ^[104] However, NWS Birmingham noted the tornado caused damage which was rated EF4 with winds of 180 miles per hour (290 km/h) on the Damage Assessment Toolkit. ^[105] Due to this published wind speed difference, the winds for this tornado are set as 170–180 miles per hour (270–290 km/h).

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Further reading

• Chiu, Samantha (2013). Mesoscale and Stormscale Ingredients of Tornadic Supercells Producing Long-track Tornadoes in the 2011 Alabama Super Outbreak. M.S. Thesis (Thesis). Urbana-Champaign: University of Illinois. hdl:2142/45431.
• The Influence of Terrain during the 27 April 2011 Super Tornado Outbreak and 5 July 2012 Derecho around the Great Smoky Mountains National Park Archived February 4, 2020, at the Wayback Machine
• Thompson, Richard L.; M.D. Vescio (1998). "The Destruction Potential Index – a method for comparing tornado days (DPI)". 19th Conference on Severe Local Storms. Minneapolis, MN: American Meteorological Society. Archived from the original on March 6, 2023. Retrieved April 14, 2022.

External links

• NWS Service Assessment Archived June 1, 2020, at the Wayback Machine
• Hook–Echo.com Tornado Outbreak Overview Archived May 3, 2011, at the Wayback Machine
• Time lapse visualization of the April 25–28 tornado outbreak Archived April 22, 2013, at the Wayback Machine
• Interactive map of all the tornado paths during the April 25–28 outbreak Archived March 4, 2016, at the Wayback Machine
• Videotaped presentations on the 27 April 2011 Super Tornado Outbreak in east Tennessee and southwest Virginia Archived April 10, 2020, at the Wayback Machine (NWS Morristown, TN)

Emergency Tornado Aid

• National Red Cross
• Tuscaloosa News People Finder Archived April 30, 2011, at the Wayback Machine – Set up by local newspaper to aid in finding loved ones and friends missing in the tornado.

Memorials

• University of Alabama Holds Memorial Ceremony Honoring Students who Died in Disaster as well as First Responders

Pictures from Tuscaloosa, Alabama

• Tornado Damage in Tuscaloosa, Alabama

Video

• Overhead view of Cullman, Alabama damage Archived January 11, 2017, at the Wayback Machine
• Detailed Radar loop of Northern Alabama, Eastern Mississippi, and Southern Tennessee Archived April 13, 2016, at the Wayback Machine

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