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Are Early Season Tornadoes Increasing?

August 15, 2012
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By Paul Homewood

 

 

This year saw a spate of early season tornadoes in February and March. While the total of 160 F1+ events in the first three months of the year was higher than normal, it certainly was not unprecedented. For instance there were 168 tornadoes in the same period in 1976, and 160 in 1971.

Nevertheless it is right to ask the question, is this part of a trend towards more such occurrences.

Certainly Kevin Trenberth thinks so.

“As spring moves up a week or two, tornado season will start in February instead of waiting for April,” Trenberth told Reuters this week.

And Jeff Masters tells us

This year’s early start to tornado season is consistent with what we would expect from a warming climate.

http://thinkprogress.org/climate/2012/03/08/439053/poisoned-weather-global-warming-helped-fuel-killer-tornadoes/

 

But what does the evidence tell us?

 

 

JAN-MARCH TORNADOES_htm_374c28ec

 

While this year has been unusual, there is absolutely no trend towards more frequent early season tornadoes. And what about strong tornadoes?

 

JAN-MARCH TORNADOES_htm_540423f

If anything, the trend is declining for EF3+ tornadoes.

It may be that Trenberth is right in saying that warming will lead to more early season tornadoes. But if his theory is correct, the actual tornado statistics would suggest that no such warming has actually taken place in the last decade.

 

References

All tornado statistics have been provided by the Storm Prediction Centre.

http://www.spc.noaa.gov/wcm/#data

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