Drought is a bad thing -- unless you're talking about a tornado drought. That was the situation in 2012, when the number of twisters touching down in the continental U.S. was significantly fewer than the 30-year average (red). So far, 2013 (green) is looking pretty sparse as well, with the caveat that states in northern sections of Tornado Alley don't hit their storm stride until later in the spring and summer. Still, other than a few specific areas, the nationwide January through April tornado count is way down, 54 percent to be exact.
Pinpointing the reason for tornado droughts (and deluges) isn't always easy. Last year's drought -- the actual drought that devastated much of the Great Plains -- robbed the atmosphere of the water vapor that fuels severe thunderstorms. Since tornadoes come from thunderstorms, this key thunderstorm ingredient was missing.
This year, while the drought is still going on, it's much less severe -- yet we may be seeing another tornado drought in the making. This time, it may be the relatively cool spring air much of the nation has been experiencing. Heat is another key ingredient of thunderstorms.
As for 2014 and beyond, it's natural to wonder if shifts in the climate will make tornado activity more or less severe. The answer is not clear. Since tornadoes play out in the atmosphere, it's likely that a changing climate will also change tornado activity. But tornadoes are complicated beasts, affected not only by moisture and temperature but also by wind shear and other factors.
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