Posted on 07/03/2012 9:19:36 PM PDT by Ernest_at_the_Beach
Derechoes have been in the news in Washington as of late. No, that’s not some new breed of super bureaucrat, but it is something from a supercell sized thunderstorm that crossed several states during its lifetime. You may have seen this NOAA image already on a few news websites:
That’s a time lapse radar image capture as the storm progressed from near Chicago to Chesapeake Bay.
They’ve been known over a century, and around far longer than that. Wikipedia says that Derecho comes from the Spanish word for “straight”.The word was first used in the American Meteorological Journal in 1888 by Gustavus Detlef Hinrichs in a paper describing the phenomenon and based on a significant derecho event that crossed Iowa on 31 July 1877.
They were further refined with the advent of weather radar. Derechos are typically bow or spearhead-shaped on weather radar, and hence they are also called a bow echo or spearhead radar echo. Here’s a WSR-57 radar image from Cleveland, Ohio in 1969:
July 4, 1969 “The Ohio Fireworks Derecho” spanning MI, OH, PA, WV
A radar in Akron, Ohio observed a “bowed” echo about 35 miles northwest of the radar site at 8:30 PM on the evening of July 4th (Fig. 2). This bow echo was associated with the deadly derecho winds in the Cleveland area and was one of the first radar “bow echoes” to be documented. Date 4 July 1969 Image: Wikipedia
They are fairly common meteorological events, occurring from May to August, peaking in frequency during the latter part of June into July. According to NOAA’s Storm Prediction Center, the Washington DC area gets a derecho about once every four years:
Image from NOAA Storm Prediction Center
Here, thanks to modern radar technology and people who are interested enough to track storms on radar from start to finish, we have this life cycle of the derecho:
Timelapse of closest NEXRAD base reflectivity of the 29 June 2012 derecho. The timelapse moves from Davenport, Iowa to Richmond, Virginia over 14 hours.
Here’s a cross section, showing how the mesoscale thunderstorm dynamics make that bow echo. Image courtesy of the NOAA Storm Prediction Center page about derechoes:
What is troubling about this being linked to “global warming” is the Washinton Post Capital Weather Gang’s story by Jason Samenow, which ends with this gem:
As the intensity of the heat wave, without reservation, was a key factor in the destructiveness of this derecho event – it raises the question about the possible role of manmade climate warming (from elevated greenhouse concentrations). It’s a complicated, controversial question, but one that scientists will surely grapple with in case studies of this rare, extraordinary event.
Yet Samenow cites the same sources from the Storm Prediction Center page that I do, showing the exact same image above (after editing out the number 3). Yet somehow, he managed to conveniently ignore the historical context and the climatological frequency of derechoes on that page.
He’s gets the coveted WUWT Double BS award for his sloppy journalism.
Joe D’Aleo has more on the derecho event here at ICECAP.
UPDATE: I made an error. I got two different posts mixed up related to the heatwave, conflating the quote discussing the heat wave by Doug Kammerer (with thunderstorm radar loop in background video by Karins on the CP post) . I’ve removed the citation (and video) related to NBC Bill Karins quoted on Climate Progress. My sincere apologies for the error. My only defense is that I don’t listen to audio much anymore due to my hearing issues. Thankfully, I’ve got a big group of people that will let me know immediately that I’ve made an error, and thus I’ve heeded their advice and fixed the error within minutes of this posting. Thank you. – Anthony
Pronunciation? Is it Der’ eh ko? or is it Dar ee’ ko? Or, does it ens in cho? (as in choke)
It ends in “cho” like macho.
I looked it up on the Web, and they say that it is day-ray’-cho.
Thanks. See #23.
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