April 2011: A Now-Infamous and Tragic Month of Tornadoes

April 2011 is a month that will not soon be forgotten, and is set to go down as an historic month for tornadoes. What began as a month with a larger-than-normal amount of severe weather became what will likely be one of, if not the most, infamous “Aprils” ever for devastating and deadly tornadoes.

While severe weather can occur at any time of the year, April through June is typically the most active timeframe for tornadoes with the peak occurring in May. This is because the jet stream that steers storm systems across the northern half of our planet begins to recede farther north due to the transition to the warmer Spring and Summer seasons. During this time of the year, storm systems are steered along a path that tends to impact a greater area of the United States. Not only that, but developing storms tend to be stronger due to a greater temperature contrast between the cold polar air, and the now warmer air over most of the country. All of these overlying factors are prime ingredients for spawning powerful thunderstorms and, consequently, tornadoes.

April 2011 didn’t waste any time winding itself up. For most of the month, the jet stream was positioned in a way that low-pressure disturbance would roll down off of the Rocky Mountains into a “sweet spot” that seemed to set itself up over the southern Plains. Disturbances would move into this area and feed on a tremendous amount of warm air over land and moisture being pulled in from the Gulf of Mexico. Throw in some strong sunlight, and you’re basically lighting the fuse on a pile of dynamite. In meteorological terms, that’s exactly what we saw for the first two weeks of the month. Lines of supercell thunderstorms would explosively intensify out ahead of these developing storm systems, and then race across the Southeast, Midwest, and into the Mid-Atlantic states. What quickly became unusual about these tornado outbreaks was the type, and overwhelming amount of tornadoes touching down. The terms “long-track” and “wedge” were popping up a lot when describing these tornadoes. We even heard the term “multi-vortex” thrown around on a few occasions, and one such tornado was caught on film near Tushka and Atoka, Oklahoma on April 14. This month would go on to spawn the deadliest two-day tornado outbreak since April 5-6, 1936.

Here is where it all started. April 4, 2011 brought an incredible outbreak of severe weather. The preliminary data shown here from the Storm Prediction Center was staggering enough, as it set the single-day record for most total severe weather reports. Damaging wind was the main antagonist here with reports spanning from east Texas all the way to the Eastern seaboard from Pennsylvania to Florida. Tornadoes made up 68 of the 1,476 reports, but this was only a precursor of things to come.

The next notable outbreak, seen below, came during a 3-day stretch from April 14-16. Powerful tornadoes tore across parts of Mississippi and Alabama on the 15^th leveling communities, and resulting in dozens of fatalities. The outbreak culminated with that largest number of tornadoes ever reported in a single day in North Carolina on April 16^th. Another notable twister from this storm system was a multi-vortex wedge tornado that occurred in southern Oklahoma, mentioned earlier. Footage of this tornado can be found here.

http://www.youtube.com/watch?v=7qYfsPxfnfE

Then came the tornado outbreak from April 26-28. This is one that will go down in history with other such infamous outbreaks as the Super Outbreak of 1974, and the Palm Sunday Outbreak. Shown below is the storm reports from the worst day of the three; April 27, 2011.

Preliminary reports from April 27 alone put the number at 263 tornadoes while the entire 3-day event spawned an estimated 312 tornadoes. Hardest hit were portions of Alabama and Mississippi, but tornadoes were reported as far north as Frankfort, NY. Tragically, this outbreak claimed at least 344 lives and destroyed countless communities. The National Weather Service is still assessing damage and working to determine the exact number of tornadoes that formed. Assuming that most of these reports verify, this event will set the record for most tornadoes spawned by a single storm system. Again, preliminary reports suggest an estimated 312 tornadoes, with the previous record being 148 tornadoes spawned during the Super Outbreak of April 1974. This will also go down as the second deadliest tornado outbreak in U.S. history.

One final image I’ll close with here. The above map shows the approximate tracks of all tornadoes that occurred in April 2011. A simply staggering number of twister covering an incredible amount of territory.

With any luck, resident of the storm-ravaged South and Midwest will get a break in the coming weeks. Yes, May is typically the peak of tornado season, but one can only hope that further tragedy will not come to these areas.

Until next time…