Wednesday, September 25, 2013

Will Global Warming Gives Us More Severe Thunderstorms?

Yes, I love loud thunderstorms.
A severe thunderstorm approaches St. Albans, Vermont
in July, 2013. New research indicates
global warming might cause more frequent
severe storms in much of the U.S., including Vermont.  

But most of us don't like the severe ones that wreck houses, cut the power for a week or flood whole neighborhoods.

But a Stanford-led study says we might be in for more storms like that.

According to the Washington Post's Capital Weather Gang, a warming climate will make severe thunderstorms and tornadoes more likely in the eastern two thirds of the nation over the coming decades.

When forecasters are considering the possibility of severe thunderstorms, they look at something called Convective Available Potential Energy, or CAPE. I won't bore you with the details, but CAPE refers to the amount of heat energy available in the atmosphere.

The more heat and humidity in the air, the higher the CAPE, and all other things being equal, the greater the chance of severe storms.

Forecasters also look at something called shear when looking at thunderstorms. Shear is just changing wind direction with increased elevation.  Shear helps thunderstorms spin, and a spinning thunderstorm tends to be stronger and lasts longer than your average garden variety storm.

If you have a big CAPE number and a lot of shear, you're likely to get destructive thunderstorms.

The Stanford study echoed previous research that said global warming would increase CAPE but reduce shear.  That's a mixed result that has had researchers not knowing whether global warming would increase storms.

The Stanford study says shear would decrease in general, but in situations where the CAPE number is high, shear would tend to stay high, too. Hence more frequent and more intense thunderstorms in much of the United States, including Vermont, by the way.

Of course, the Stanford study will be reviewed by other scientists, who might draw other conclusions.

Which leads me to a larger point: While scientists pretty much agree that man made global warming is occuring and bad stuff will result, there's still a lot of disagreement on exactly what kind of bad stuff will happen.

Yes, there's a general idea that the warming will cause bigger and more intense weather extremes, but what that means for a particular area is not always 100 percent certain. We only have educated guesses and general ideas, which of course makes planning for climate change that much more difficult.

And, just for "fun," I guess, here's video I shot of a severe thunderstorm in Burlington, Vermont in July, 2012.

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