It's been a little over a week since the second deadliest March tornado outbreak in U.S. history occurred. Tornadoes dropped from the sky from the deep south to the Ohio River Valley. The death toll is 41 people with most occurring in Indiana and Kentucky.
Crews from the National Weather Service have been busy the past week sifting through the damage and debris left behind by these twisters. Their goal is to try to write a history of each tornado detailing the time it touched down and died, its size, strength, and much more. So far 60 tornadoes have been confirmed from March 2nd. Most were fairly weak, but there were several that were considered especially strong. Nine tornadoes were EF-3 and two tornadoes were powerful EF-4 tornadoes.
There were 159 reports of tornadoes that day. Quite worthy of a high risk the Storms Prediction Center had put out for the day. The tornadoes were triggered by warm and moist are being pulled up from the Gulf of Mexico by a large and powerful low pressure system. The low pressure system was enhanced by a very vigorous and fast moving jet stream ahead combining all the ingredients necessary for a tornado outbreak. The thing is...it was early March! Rare to see an outbreak like this so early in the year. Not the case so far in 2012.
This tornado outbreak will be most remembered for the twin super cells that followed nearly the exact same path across Southern Indiana. One of the super cells spawned an EF-4 tornado that decimated the city of Henryville, IN. You can see a map of the damage path of the EF-4 tornado that went through the town above. Notice that second area of damage with the white track and red border south of Highway 160. There has been video showing this was a multivortex tornado and confirmed also by the damage. That means there are smaller spin up tornadoes that circle around the main funnel. What is so dangerous about these spin ups is that there winds can be even faster than the main tornado and can create very localized and massive damage as they spin up around the main funnel. That was the case with Henryville and would help to widen the tornado as it exited the city. Below is a picture looking east as the tornado crossed N. Ferguson street by the high school.
This one EF-4 tornado carved a 49 mile path from Fredericksburg, IN to Bedford, KY. Maximum winds were as high as 175 mph and the tornado's max width at times was 0.4 miles. This wasn't the only tornado that would go through Henryville that day. Notice the map below. You can see two textbook supercell thunderstorms with a perfect hook shape following nearly the same path, one after the other. The second supercell would come through Henryville within an hour of the other supercell that produced the EF-4 tornado. The second tornado was a weaker EF-1 tornado, and it's path is shown on the map farther up in this blog post. It is very rare for something like this to happen. The town of Henryville had never been hit by a tornado, and in one day they were hit by two.
It's been a very fast start to the tornado season so far in 2012, and already we are well ahead of normal for the year. Tornado season typically really start to ramp up as we get in April across the country.