05.22.10

Tornado Season So Far…

Posted in Weather News at 3:31 pm by Rebekah

Just over a month ago, I posted on the unusual lack of tornadoes through mid-April.  As expected, however, shortly after that post, there was an explosion in this year’s tornado count.

Here’s how we stand through Thursday, May 20 (does not include the 5 tornado reports from yesterday).

This graph (click to enlarge) from the Storm Prediction Center shows the trend in local storm reports (LSRs) of tornadoes in the U.S.  LSR values may be slightly higher than the actual tornado count, as some tornadoes may have been reported more than once.

The next graph, also from the Storm Prediction Center, shows annual tornado trends and percentiles; calculation details are at the website at the bottom of the figure.  The red line is the maximum tornado count in a single year and the pink line is the minimum tornado count in a single year.  The other lines show tornado trends in quartiles.

Note that after briefly dropping below the all-time minimum, this year’s tornado count quickly jumped up in late April, and we’re now approaching the 25th percentile.

Although it looks like we’ll be getting a big ridge over the central US this coming week, inhibiting widespread severe storms for at least the next couple of weeks (though there are still likely to be localized areas with severe weather), the storm season is not over yet.  There is usually a ridge that comes for a week or two in May, before another peak in tornado season comes in early or mid-June across the Central to Northern Plains.

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