29 April 2011
Madison County, AL is in the dark tonight. Every main feeder line into the area was destroyed by the tornadoes yesterday, and you can walk outside and see the sky the way my great grandparents saw it 90 years ago! I am writing this post using the generator that is running the five lights in our studio, and (we are told) no power is likely for at least 4 days.
It looks like the deaths (and damage) were the result of three main long track tornadoes on Wednesday. There were a bunch of others, but a first look seems to indicate that 3 individual supercells crossed North Alabama. Each cell produced numerous EF 4 and EF 5 tornadoes, and it’s possible they produced at least one long track tornado. NOAA has people coming in to do a detailed storm survey and rate the tornadoes, but the aerials I have seen so far indicate EF 4 at least.
The video above is the tornado that hit Cullman, AL around 2:45 PM on Wednesday. The Doppler velocity image at the same time shows what meteorologists call a TVS — Tornado Vortex Signature. Notice the intense winds of 50 knots toward the radar, (blue) adjacent to the 50 knots away from the radar, (red) over Cullman. The base reflectivity image showed a classic BWER (bounded weak echo region) and a pronounced ” hook echo”.
This same storm moved into Marshall and Dekalb Counties and caused numerous deaths. This is a classic large tornado signature on radar, and the only question when you see something like this is how strong a tornado it will be. In this case, it turned out to be very strong, and likely violent, with winds near 200 mph.
The CIMMS Satellite blog has an amazing MODIS image (visible channel) with the tornado paths visible.
More on the deadly outbreak tomorrow.