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NSSL
The impact of global warming on tornado activity by Martin Lisius
It will probably take at least another decade before we are certain that global warming or a "climate change" is really underway across the plains of Tornado Alley. This region, which stretches from Texas to the Dakotas, is where more tornadoes occur than anyplace on earth thanks to the common interaction of three air masses. It is here that we can most easily study any significant climate change and its impact on tornado activity.
Just a few years ago, March 1st was considered by many storm chasers to be the unofficial start of tornado season on the Plains with the peak occuring from about mid-April to early July. However, since 2005 it is clear that spring is starting a little earlier. In fact, I have seen more tornadoes in March and April during this period, all in Texas. And, in 2009 I intercepted my first February tornado since I began chasing in 1987. It appears that the tornado spring season in Tornado Alley is now longer.
If global warming actually exists, then its logical that the Gulf of Mexico will be warmer than the previous norm. A warmer Gulf would lead to sufficient instability across Tornado Alley probably for a longer period of time each year. An earlier return of warm, moist air onto the Plains means an earlier spring. As long as rich Gulf air and moderate to strong westerly winds aloft come together, tornado season will remain in place.
For now, I believe strongly that the tornado season for Tornado Alley begins approximately mid-February and ends in late July with the peak running from mid-March to mid-July. Texas will continue to experience more tornadoes than any state, on average. There may also be a slight easterly shift to average tornado activity favoring areas of lower elevation than the previous norm, although I would like to monitor activity for a few more years before committing to that opinion.
March-April tornado intercept summaries since 2005:
Lamb-Hale-Swisher County, Texas tornado intercept, April 21, 2007
Brisco - Donley County, Texas tornado intercept, March 28, 2007
Thornberry, Texas tornado intercept, April 24, 2006
Paris, Texas tornado intercept, March 21, 2005
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