With the hot air swelling and spreading the storm, rain continues to fall behind the derecho. This forms a cold pool behind the storm front -- "like a bubble or a dome of cooler air," according to Herzmann -- that, in turn, allows more downbursts to form and the cycle to repeat itself.
Looking at radar images of the derecho, the system appears as a kind of boomerang-shaped band of high-intensity winds with a circular, cooler mass of air behind it. That boomerang -- called a "bow echo" by meteorologists -- is in fact a long line of clustered downbursts, each 2 to 4 miles wide.
That makes the derecho easy to identify, although given the speed with which one can form, that doesn't necessarily give communities much time to prepare, said Herzmann.
"The problem is that, on any given day, you're going to see small weather events that have the potential to turn into a derecho," he said. "It's still really hard to know which ones are going to roll into the full-fledged derecho and which ones will just dissipate."
No one could say climate change was the direct cause of this storm, but rising temperatures and more powerful storms have been predicted by climate models for more than two decades.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
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Add CommentThere are some issues with this article which surprised me that SA would publish it. First the article does not state what a "super derecho". Having taken meteorology classes is just a specific type of severe weather, I have never heard the term "super derecho" before this article. Related to that while derechos are rare in the Mid-Atlantic they are not as rare as the article would leave you to believe and bow echos can form without the storm being a derecho. Derechos happen frequently in the Central US, this link is to the NWS fact page on derechos(http://tinyurl.com/ckrbzn). Finally the video that is included in the article is a radar image, but it is a reflectivity radar image. This video is not showing wind speeds but the amount of precipitation that is aloft in the atmosphere, with the red showing the highest reflectivity.
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