How common are EF-5 tornadoes?

The video and images coming out of Moore, Oklahoma are almost surreal. You may be thinking how can wind do such incredible damage? Or how can cars be piled up against the side of a hospital? Or how can a metal beam turn into mangled debris?  Tornadoes like the one that struck Moore on May 20, 2013 are very rare, though Moore has the unlucky distinction of being ground zero for two of them since 1999.

On average the United states sees 1,253 twisters per year (according to NOAA’s National Climatic Data Center). Since 1950 when modern record keeping of tornadoes began, a total of 59 EF-5 (and F-5 using the old scale) tornadoes have been identified. That’s less than 1 per year. Grabbing a calculator and crunching the numbers will show you 1 out of every 1,359 tornadoes grows into an EF-5 in the United States.

EF-5 tornadoes most often occur during large tornado outbreaks when conditions are favorable for multiple tornadoes over a large area. On April 27,2011 a total of 4 EF-5 tornadoes struck the southeast. On April 3, 1974 (the original Super Outbreak) a total of 7 EF-5s carved up the ground from Alabama to Ohio.

EF-5s usually do not appear out of nowhere with little warning. Meteorologists at the National Weather Service in Norman, OK issued a tornado warning 16 minutes before the funnel touched down and 36 minutes before it ripped through Moore. Yet some national news outlets still used the phrase “it struck without warning”, ugh!

The 59 (E)F-5 tornadoes in the U.S. since 1950 from earliest to most recent. Credit: SPC

But what about here in Wisconsin? We are not in tornado alley but certainly not immune either. Well, we have seen our fair share. Three top of the scale tornadoes have hit different corners of the Badger State: Oakfield in 1996, Barneveld in 1984, and Menominee in 1958. Looking pre 1950 when tornado assessment wasn’t quite as accurate, it is likely another 3 F-5s struck in 1899, 1898, and 1893, all in the same decade!

While it’s unlikely any of us will see an EF-5 up close and in person it is important to know it can happen. It doesn’t matter if you live by the lake, in a valley, or if you think storms just always seem to miss your town. Geographic features do not create an invisible force field that deflects bad weather. Devastating tornadoes have occurred and will occur in our part of the country. Having place to go and plan to follow when one does strike is a must.