Four US states were hit by powerful tornadoes, which tracked across a wide swath of the midwest and south during one of the largest March outbreaks of tornadoes ever to be recorded. During the 2nd-3rd March a tornado outbreak ravaged the Tennessee Valley, the Ohio Valley, and parts of the South. It will go down in the record books as one of the worst, if not the worst, March tornado events on record.
The outbreak began fairly early on the morning of 2nd March, with an initial round of storms and tornadoes associated with a warm front and a rapidly deepening depression over the Great Lakes. As the strong warm air mass entered the region, temperatures rose to near record levels for early March and the atmosphere became very unstable with extreme wind shear. This resulted in a second, much larger, line of discrete supercells near the Ohio River, and additional storms developing further south. These cells tracked eastward across the Ohio Valley, passing near Louisville, Kentucky and south of Cincinnati, Ohio with devastating results.
Activity further south led to the development of intense supercells in central Kentucky in the late afternoon that tracked east. This area experienced the highest wind shear allowing the storms to spin violently, resulting in severe damage in several communities.
On 3rd March, the cold front continued to push eastwards toward the east coast, although the most severe activity took place near the Georgia-Florida state border with damaging wind gusts. By 4th March 4, the cold front had moved into the Atlantic Ocean and this particular tornado event came to an end.
It resulted in 56 confirmed tornadoes - although this total may rise as officials assess data and reports from the event. The record for the largest March outbreak is 74 from March 11-13, 2006 and the number observed on 2nd March comes close to the all-time single day March record of 59 tornadoes on 31st March 1990. The 10 year tornado average in the US during the entire month of March is only 87 tornadoes. The record for the entire month of March is 180 tornadoes set in 1976. This week's violent storms raised fears that 2012 will be another bad year for tornadoes after 550 deaths in the US were blamed on twisters last year.
The most violent tornado of the outbreak was an EF4, the second highest category in the Enhanced Fujita (EF) scale used to rate the strength of tornadoes, that carved a 49mile path of damage through Indiana and Kentucky. Along its track, the tornado destroyed hundreds of homes and killed more than 10 people. The most severe damage took place in the small communities of Henryville and Chelsea, Indiana. The wind strength was estimated at 170mph.
And, as if to add insult to injury, several inches of snow fell over southern Indiana and Kentucky after the tornadoes had done their damage, challenging the clean-up effort.