Perfect weather conditions - warm, moist air rising and mixing with colder, dry air at higher altitudes- are being attributed to the more than 150 tornadoes that ripped through the Southern States of Mississippi, Alabama and Georgia on April 27th, 2011 - And the assault continued until Saturday morning, when the storms finally petered out to light rain.
Amongst the hardest hit was the city of Tuscaloosa in Alabama, where a mile-wide twister that reached 7.5 to 9.5 miles into the sky, zoomed in at winds exceeding 260 miles per hour, destroying everything in its path and injuring over 800 residents. Classified as an F5 or the most severe on the Fujiita scale, which ranks tornadoes based on wind speeds and destruction, the twister originated just southwest of Tuscaloosa. While most tornadoes usually touch the ground for a few minutes before they dissipate, experts believe that this one may have lasted for a record-breaking 300 miles and maybe the same one that swept across Alabama and Georgia.
While tornadoes are pretty common in this part of the world, the severity of the recent ones was what took everyone by surprise. Given that the residents had only a 24-minute lead time before the big one hit, there was little they could do but hunker in the safest possible places. For some it was the church, while for others it was inside a car. While some made it, others were not so lucky - It is estimated that over 300 people lost their lives. What's a little concerning is that this is just the beginning of the US tornado season that lasts until June - Hopefully, the worst is over first!
WHAT ARE TORNADOES AND HOW ARE THEY FORMED
A tornado is a very powerful rotating column of air that starts from the bottom of a thunderstorm cloud and extends all the way down to the earth. They form only during very severe rotating thunderstorms, called supercells that occur when cold dry polar air comes in contact with warm moist tropical air.
As the warm air rises, winds around the storm cause it to rotate and form a funnel. The air in the funnel spins faster and faster, creating a low-pressure area, which sucks in even more air and sometimes even objects.
While ordinary thunderstorms last between 30-60 minutes, supercells develop many updrafts and downdrafts and can live on for hours.
While tornadoes occur all over the World, the U.S. gets the most, about 1,200 a year. The worst hit area is a stretch of land known as Tornado Alley that extends from Texas to South Dakota. Here the dry air off the Rocky mountains meets warm, moist air from the Gulf and cold Arctic air from the north - Perfect conditions for storms that are powerful enough to turn into tornadoes.
Resources: NationalGeographic.com, huffingtonpost.com, telegraph.co.uk, CNN.com