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Tornado Go?
Fri May 21, 2004
Listen in RealAudio 
When it comes to tornadoes, we’ve had a string of droughts lately. And that’s a good
thing, says correspondent Bob Henson.
BH: Only a storm fanatic could be upset when Tornado Alley turns into an empty
boulevard. That’s what happened in the past year—not once but twice. In 2003 there
were two long periods without a single tornado observed in the U.S. The first tornado
drought, early in the year, lasted 45 days. An even longer drought went 50 days, from
Thanksgiving Day to January 15. It’s the first time we’ve had two such droughts in
a single year since modern tornado records began in 1950. But a tornado drought
doesn’t mean the crops will fail, according to Harold Brooks of the National Severe
Storms Laboratory.
HB: Tornado droughts aren’t necessarily associated with a lack of precipitation. It’s
just that we aren’t getting tornadoes. Frequently, years may have thunderstorms
occurring, but they just aren’t tornadic. But the atmospheric conditions to produce a
tornado aren’t the same as those that we have to have to produce an ordinary
thunderstorm. And so you can have lots of thunderstorms or lots of rain occurring
without thunderstorms and still not get tornadoes.
BH: Still, there could be important climate signals hidden in the waxing and waning of
tornado frequency, says Brooks.
HB: One of the questions we’d really like to be able to answer is what‘s the frequency
that we should expect to see droughts of tornadoes? How frequent should they be
occurring and do things like this provide us any kind of an answer to changes in
climate or are they happening less often than we think they should be ordinarily. We’ve
got a big
problem with the fact that our record of high-quality observations isn’t as long as we’d
like it to be, and so these are very difficult questions to answer, but they’re ones we’re
trying to look at.
Bob Henson lives in Boulder, Colorado. The Weather Notebook is produced with
funding from The National Science Foundation and Subaru of America. Special funding
comes from Davis Instruments, at www.davisnet.com.
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