Extreme Tornado Outbreaks Are Becoming More Extreme


December 1st, 2016 Climate Central Andrea Thompson

Outbreaks of tornadoes — where multiple tornadoes form over an area in just a few hours or days — are responsible for most of the devastating destruction caused by severe weather, and a new analysis has reached a worrying conclusion about the worst of these outbreaks.

Outbreaks with many tornadoes are becoming more extreme, particularly the very worst outbreaks, according to a study published Thursday in the journal Science. When researchers looked into what might be causing the trend — and whether it could be linked to expected changes in storm environments due to climate change — they found the opposite of what they expected, pointing to the need for more research on the matter….

…Climate models have suggested that instability should increase with warming, because of the excess water vapor a warmer atmosphere can hold, but that wind shear should decrease. The increase in instability was seen to win out, though, suggesting it could be behind the tornado trends. But when Tippett and his team looked at trends in particular atmospheric measures of these two factors, “we found the opposite,” he said: Wind shear was behind the trends in extreme outbreaks.

…The finding suggests that either climate change isn’t causing the observed trends, or that scientists still don’t have a good handle on how climate change may alter the storm environment….

Tippett et al. More tornadoes in the most extreme U.S. tornado outbreaks. Science  01 Dec 2016: DOI: 10.1126/science.aah7393

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