26 April 2011

60 years of tornado touchdowns

Several months ago I posted a map of tornado watches over a ten-year period.  Here's an even-longer-range perspective:
This distribution of tornadoes often feeds into the myth that mountains protect communities from tornadoes. In fact, the more rugged terrain of the mountainous region does not disrupt tornado tracks or prevent formation of tornadoes; however, the slightly cooler and drier climate leads to conditions less conducive to formation. In other words, the relative lack of tornado touchdowns in mountainous regions is because of the weather, not the terrain.
Via Paul Douglas' On Weather blog.


  1. Isn't the weather partly derived by the terrain itself?

  2. Timeshadows, down here in North Central Texas, where we are having a spate of rainstorms and tornadoes, geography does make a difference -- we are caught between the Rocky Mts. and the Gulf Coast, on the plains where the weather fronts clash.

  3. @Dallas Jerry: Thanks. :)
    --Keep your heads down and stay safe! :D

  4. This map leaves a lot to be desired. Sure, the Atlantic region is "relatively active" compared to the Appalachians, and at first glance it seems like the East Coast may even contend with the Midwest for tornado incidents. But a real analysis of the data would require consideration of at least two other important variables: strength and duration of the twisters. If you weighted each incident by these factors, I have no doubt that the dots east of the Mississippi would dwindle to little specks. Data visualization, for good and bad, is an artistic take on hard data, and can do wonders for education but can also mislead. It takes a very careful person to create a good map, and a very skeptical one to spot garbage.

  5. Chris, this map comes from the Storm Prediction Center at the National Oceanic and Atmospheric Administration's National Weather Service.

    Here's the link -


    You might write to them with your concerns with the data.

  6. Timeshadows,
    My thoughts as well. Terrain has a huge impact on weather, so even if it's one step back on the sequence, that doesn't make it a myth.

  7. Here in CA, we have gotten a few tornados that I am aware of. In fact, in December I believe we had a tornado warning near my area. What interests me most is that the tornado activity seems to be concentrated in the Central Valley and the southern coastal region. Very interesting.


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