April 27, 2011 was the deadliest day of the outbreak, a total of 199 tornadoes resulted in the deaths of 319 people across 14 states.
It was one of the most intense weather events in U.S. history.
From April 25 to April 28, 2011, 358 tornadoes touched down across 21 states, and by the time it was over, 324 people had died and enough damage had been done to rank the outbreak as the costliest yet recorded.
Meteorologists were well aware of what was coming, to the point that it was scary to look at the models as the time approached.
"The conditions were ripe for a widespread severe weather outbreak" says Doug Gillham, a meteorologist at the Weather Network who was teaching at Mississippi State University at the time of the outbreak. "We had a strong jet stream, very warm and humid surface conditions and strong winds at and just above the Earth’s surface. The wind direction also turned as you went up in the atmosphere, which is what caused the storms to rotate.”
Meteorologists were alarmed by the computer model guidance that they were receiving during the days prior to the storm.
For example, the Energy Helicity index, which is used to forecast the threat for supercell thunderstorms by comparing vertical sheer and instability, is considered high at a reading of five. For this system, the model guidance was forecasting values higher than 12.
The storm system came in several rounds over a four day period.
The outbreak began April 25, striking the traditional “tornado alley” region, notable damage was done in Arkansas, where the town of Vilonia was severely damaged and four people were killed.
April 26 saw numerous tornadoes touch down across Texas, Louisiana, Arkansas and several other states, while heavy wind and hail damage was reported in New York.
That night marked an increase in the severity of the system as winds picked up speed and widespread power outages were reported.
Despite all the destruction of the previous two days, April 27th was the deadliest of the outbreak. A total of 199 tornadoes resulted in the deaths of 319 people across 14 states.
Although Gillham had been keeping his family updated on the system as it unfolded, on the night of April 26, they prepared by gathering their safe and family albums. An hour before the storm hit their town in Mississippi, Gillham called his family and had them come to seek shelter with him on the campus of Mississippi State University.
“I grew-up in Southern Ontario where I learned at an early age that one should seek shelter in a basement if there is a tornado threat, but in the southern U.S., most houses do not have basements. Fortunately, my office was in a building that was built into the side of a hill, so we could get below ground level.”
In all, 37 of the tornadoes to touch down that day were rated as EF3 or stronger.
11 tornadoes were rated EF4 –- between 267 and 322 km/h -- and four were rated EF5 –- more than 322 km/h. The average EF4 and EF5 tornado path length was a massive 106 km.
Fortunately for Gillham and his family and friends, the strong rotation was not in contact with the ground as the storm tracked right over MSU, but many other places were not so fortunate. Tuscaloosa, Alabama, along with the University of Alabama, was particularly hard hit that afternoon.
Wind gusts over 110 km/h managed to topple a tractor trailer and close the Burlington Skyway
Outbreak also affected Canada
In Ontario there were two deaths reported as a result of the system.
One tornado touched down in the community of Fergus on April 27, and then winds of up to 124 km/h caused severe damage in the Niagara region.
The winds were so strong that the Burlington Skyway had to be closed in both directions because the high gusts rolled over a tractor trailer.
For Gillham, the storm had a double personal connection.
“In Mississippi we were fortunate that my town escaped serious damage but over in Niagara where I was born, my parents’ home suffered roof damage and property damage from the high winds.”
At the end of it all, the storm resulted in damage costing $11 billion over an area that spanned from Texas to New York, and up into southern Ontario.
It would officially be classified as the costliest tornado outbreak to date, and the fourth deadliest.
What was most unfortunate for Gillham was that, despite the long lead time on the warnings, the death toll was still immense.
If any positives can be drawn from the outbreak, he says, it’s that more research is being conducted, with collaboration between meteorologists and social scientists to work on ways to more effectively reach the public with warning information.
“In addition to increasing forecast accuracy, we need to address the perception that many people have that a ‘tornado will never hit me,’” he said. “It is our job to ensure that we reach as many people as possible with the information that they need to make decisions that could save their lives.”
Tornado outbreaks such as the 2011 episode have occurred before, such as the 1974 “Super Outbreak,” and a 1925 outbreak that was the deadliest in U.S. history, with 695 fatalities reported.
You can be sure that deadly tornado outbreaks will happen again but as technology and people’s attitudes evolve, hopefully more lives will be saved.