Overall, tornado season low-key

  • Article by: BILL MCAULIFFE , Star Tribune
  • Updated: October 14, 2011 - 1:59 PM
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A tornado ripped through north Minneapolis last May.

Photo: Kyndell Harkness, Star Tribune

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The May 22 tornado that ripped through Minneapolis, killing one person, injuring 48 and damaging hundreds of homes, made 2011 an exceptional tornado year.

But the season was also about average. In fact, it was tame compared with 2010.

The state has seen 31 tornadoes this year, according to Todd Krause, warning coordination meteorologist for the Twin Cities office of the National Weather Service. That's only four above the 60-year average. Only about 1.6 percent of Minnesota's tornadoes occur in October, so it's a safe bet that the season is over.

Last year, Minnesota led the nation for the first time, with 113. More than 40 -- more than an average year's worth-- occurred June 17, including three EF4s, each the strongest individual tornado in Minnesota in a decade. Three people were killed.

This year, Minnesota saw only two tornadoes rated as high as EF2. The Minneapolis tornado was one of a dozen scored EF1. The rest were EF0. June, normally the state's heaviest tornado month, brought only one.

Straight-line winds picked up some of the destructive slack. A blast in northwest Minnesota Sept. 1 included a gust measured at 121 miles per hour, possibly the strongest ever withstood by a measuring instrument in Minnesota. That's equivalent to an EF2-scale tornado. Three similar windstorms caused widespread damage on July 1, July 10 and Aug. 1. High humidity generated the severe storms. While afternoons are more suited to tornado formation, Krause said, these storms tended to be in the morning or at night.

The U.S. tornado season saw apparent record fatalities in April and May. Unofficially, the United States has seen nearly 1,300 tornadoes this year; average is 1,000. (Tornado counts are rising, largely due to better detection.) More than half were in April.

"Every year is odd," national tornado expert Thomas Grazulis said. "Minnesota had its turn [in 2010]. It'll wait for a generation now, until Minnesotans no longer remember that."

Bill McAuliffe • 612-673-7646

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