Tornado outbreak of April 14–16, 2011

From April 14–16, 2011, a tornado outbreak, among the largest recorded tornado outbreaks in U.S. history, produced 178 confirmed tornadoes across 16 states, resulting in severe destruction on all three days of the outbreak. A total of 38 people were killed from tornadoes and an additional five people were killed as a result of straight-line winds associated with the storm system. The outbreak of severe weather and tornadoes led to 43 deaths in the Southern United States. This was the largest number of fatalities in an outbreak in the United States since the 2008 Super Tuesday tornado outbreak. However, this outbreak was soon surpassed no more than two weeks later by the 2011 Super Outbreak, which killed 324 people.

Meteorological synopsis

April 14

On April 14, a strong storm system in the southern section of the Rocky Mountains moved east to the central and southern Great Plains region during the afternoon and to the mid and lower Mississippi River Valley during the overnight hours. The system was accompanied by strong winds in the middle and high levels of the atmosphere along with cold upper air temperatures. With these elements coming together with moisture moving north from the Gulf of Mexico, it resulted in conditions favorable for severe weather. A moderate risk of severe weather was issued for that day by the Storm Prediction Center as a result across eastern Oklahoma and neighboring parts of Arkansas, Kansas, Missouri and Texas. With a dryline extending from southern Kansas to Texas, thunderstorms began developing along the dryline across north and south central areas of Oklahoma by 3:10 pm CDT (2010  UTC). These storms would form into supercells and move into eastern Oklahoma by 4:00 pm CDT (2100 UTC).

Storm chasers in the region reported multiple funnel clouds and two touchdowns, neither of which resulted in damage. Several tornadoes were confirmed through storm chaser video and local emergency management services. A large, intense tornado later caused severe damage in and around the towns of Atoka and Tushka. Many houses were destroyed or flattened from what was at times a double tornado with two well-defined vortices. Numerous injuries were reported in the latter of these areas. Two died and 43 more were injured in Tushka. In Arkansas, strong winds produced by thunderstorms killed at least seven people. Of those deaths, five were confirmed to have been from straight-line winds and two were as a result of a weak tornado embedded in an overnight squall line that tracked across the state.

April 15

A moderate risk of severe weather also existed for April 15 across much of Alabama and Mississippi. During the pre-dawn hours into the morning of April 15, tornadic activity temporarily waned with only isolated activity. However, by late that morning, supercell thunderstorms developed again over parts of Mississippi, and tornadoes began to touch down again. A tornado emergency was declared for the northern Jackson metropolitan area shortly after 11:00 am CDT (1600 UTC), as a result of a widely photographed tornado that moved through parts of the city and the adjoining city of Clinton. The destructive tornado moved across the area producing severe damage and numerous injuries according to WLBT coverage. That afternoon, Mississippi State University spotters confirmed another large tornado in east-central Mississippi and west-central Alabama and the second tornado emergency of the outbreak was issued. ABC 33/40 coverage reported that the tornado was 3/4 mile (1.2 km) in width.

Two additional tornado emergencies were also issued that afternoon for other storms in Attala County, Mississippi, and Choctaw County, Alabama, and a fifth such issuance occurred near Leakesville, Mississippi, that evening, where a large EF3 wedge tornado produced severe damage and 4 fatalities. Local storm reports report at least 7 fatalities from the storms on April 15.

April 16

The next day, a moderate risk of severe weather was issued for April 16 for the Carolinas and southern Virginia as the cold front tracked eastward and a mesolow developed across the Appalachians. As storms began moving into areas of strong atmospheric instability, a PDS Tornado Watch was issued shortly after noon and a high risk, the first of 2011, was issued shortly thereafter at 12:30 pm EDT (1630 UTC) for central and eastern North Carolina and immediate adjacent areas in South Carolina and Virginia. A squall line descended the Blue Ridge, and rapidly intensified along the Interstate 77 corridor.

As this line tracked eastward, wind damage was reported in Salisbury and Lexington, where tree and roof damage was widespread. The Salisbury storm - an EF1 - became the first confirmed tornado from the outbreak in North Carolina, followed shortly thereafter by tornadoes near Monroe (EF0) and north of Burlington (EF1). The Burlington area storm would mature into the first of multiple long-tracked, multi-tornado tornadic supercells, producing additional tornadoes near Roxboro and South Hill, Virginia.

Moving rapidly to the east, the squall line entered areas that had experienced sunnier weather earlier in the day, and the squall line began to rapidly fragment into powerful discrete supercells by early afternoon. Explosive wind shear also made the atmosphere extremely prime for tornadic development. At about 3:15 pm EDT (1915 UTC), a tornado emergency - the sixth of the outbreak - was issued for an especially intense tornado in the Raleigh-Durham metropolitan area. This cell had developed in Moore County, and had at one point been a very strong tornado - a high-end EF3 twister - in the city of Sanford. A very prominent hook echo was easily visible on local radar returns, with a hail core and debris aloft also reflected in radar imagery.

This storm, which may have been a mile wide, tracked through the southeast edge of downtown Raleigh, on a southwest-to-northeast trajectory that passed through miles of suburbs surrounding the city. While damage in Wake County fluctuated between EF0 and EF2, it was accompanied by debris fallout from the Sanford area, when the storm was far more violent. Tracking through Raleigh, the tornado crossed three interstate highways, and narrowly missed a nuclear power plant as it moved from southwest to northeast through the densely populated (900,000+ population) county. The campus of Shaw University in downtown Raleigh was so severely damaged that classes were suspended for the remainder of the semester.

Soon afterwards, two additional tornado emergencies were issued farther south and east, as radar images of the developing supercells indicated very prominent hook echoes. Of the larger cities in eastern North Carolina, Fayetteville, Jacksonville, and Wilson all endured direct hits from EF2 or EF3 tornadoes. A tornado or tornado family that began in the city of Fayetteville, briefly closed interstate 95 in Johnston County, due to debris blocking the highway.

Late in the outbreak and farther into northeastern North Carolina, another EF3 tornado in Askewville, North Carolina, in rural Bertie County caused 12 fatalities and extensive damage in the towns of Askewville and Colerain, just west of the Chowan River

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