In 2012 we tried not to be alarmist about the circumstance that tornadoes and hurricanes are deadlier and more frequent that in previous years. We acknowledged that there was a lot that meteorologists did not know about the formation of these extreme weather events. After reading scientific information about the formation of tornadoes, we concluded that climate change was a contributing factor to their formation and destructive power.
We wrote three blogs on the subject that you might like to review before reading our comments on the 2013 tornadoes, written after review of more recent scientific commentary on this outbreak.
The US South West, particularly Oklahoma, is the spawning ground for North American tornadoes. There the warm, moisture-filled air from the Gulf of Mexico meets the easterly flow of cold air over the Rockies (the Rockies system). The meeting of these two weather-forming influences creates a wind shear that generates the rotation characteristic of tornadoes.
A warmer climate will increase moisture carried by Gulf of Mexico systems, but may also increase the temperature of the Rockies systems, potentially reducing the temperature differential that is all-important to the development of wind-shear. Perhaps the Gulf of Mexico influence will predominate: the destructive tornado that hit Moore, Oklahoma on May 20 was in the highest category for wind speed and one of the largest ever in ground coverage.
More evidence is required before meteorologists can tell you if reduced wind-shear will lessen the numbers and turbulence of tornadoes. So the consensus seems to be that climate change and “natural variability” will continue to contribute to the formation of tornadoes.
Mind you, even meteorologists who hypothesize that wind shear will be reduced acknowledge that if a tornado does not result, there will probably be severe thunderstorms instead. In the case of the destructive tornado that hit Moore on May 20, by May 21 the threat shifted to strait line winds, such as are found along a line squall.
As a bit of cautionary advice, remember that Ontario is the terminus of Twister Alley!