Weather Ready Nation: Tornado Warnings by CWAs

Posted by on 15 Dec 2011 | 1 comment

Tonight’s blog post depicts the number of tornado warnings issued by year by CWA. I should add a disclaimer: I am using the current CWA boundaries for all prior years. Thus, it one runs the risk of making incorrect assessments if one directly compares the specific increase in CWA tornado warnings counts. Instead, the idea is to look at the general trend in the number of warnings issued by forecast offices.

Data for 2007 and later years need to be understood in the context that WFOs have switched from county-based warnings to storm-based warnings. Thus, it is possible to have situations where multiple storm-based warnings are in effect when in the past a single county-based warning would have been issued. The flip side to that is, a single storm-based polygon can now capture 2 or more counties, which would have required multiple county-based warnings in the old system.

As I mentioned last night, the number of warnings issued can be thought of as a cumulative measure of the number of times the NOAA Weather Radios would have sounded in a specific CWA. Thus, the increasing number of warnings issued can be thought of in terms of the National Weather Service requesting more responses from the residents in their CWAs.

The images begin with 1986 in the upper-left and increase from right-to-left ending with 2010 in the bottom-right.

Tornado Warning Counts by CWA (1986)

Tornado Warning Counts by CWA (1986)
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  • http://twitter.com/memphisweather1 MemphisWeather.net

    Patrick – Excellent presentation. Would love to see these normalized by area, especially the past decade or so. As you know, larger CWAs (by area) could be expected to produce more warnings as they cover a larger region. Also, would be interested in a summation ofthe past 10 years or so for each CWA. Jackson, MS is knocking it out of the park (not sure if that is good or not)! I’m surprised by these stats, though perhaps should not be living in Memphis.

    Thanks for the excellent info!

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