The term "derecho" was not in my vocabulary until the evening of June 29, 2012, when the Washington, D.C. area was blasted by a storm system that had begun in Iowa that morning.

The straight-line wind on a day when storms were unexpected, was astonishing (70-80 mph around in and around DC) and few people knew it was going to happen until a couple hours before it did, if then, at 10:30 p.m. on a Friday night.

In just Virginia, DC and Maryland, over 2,000,000 power company customers were left in the dark and without air conditioning and refrigeration -- amidst a heat-wave that would continue for the next week. Many friends were without power for several days and some were trapped on their streets until fallen trees could be moved out of the way. My neighborhood was largely unscathed because our power lines are underground yet within a couple of days our nearby service stations were running out of gas because of people coming in from the 'burbs to fill up (gas stations in the affected areas also lost power).

That derecho was the most significant natural disaster, by far, since I moved here thirty years ago. And I hadn't even known what a derecho was. So it was with keen interest today that I saw reports of a derecho in Iowa and Illinois (where the 2012 derecho formed). If you're in the midwest or east coast, this is a phenomenon to be familiar with.

Report on today's derecho in the midwest:

http://www.washingtonpost.com/blogs/capi...ne-force-winds/


Below is a National Weather Service in-depth after-action report on the 2012 derecho. It is largely self-critique of their performance and recommendations for improvements. It includes a highly detailed retrospective on the formation and effect of that derecho. Interesting reading for weather-geeks (myself) and the preparedness-minded (presumably most ETS-ers)

National Weather Service report on the 6/29/12 derecho

http://www.nws.noaa.gov/os/assessments/pdfs/derecho12.pdf



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As a resident of the DC Metro area, I second Danny's warning. The 2012 event brought down more tree limbs (from apparently healthy trees) than any of the several hurricanes we have experienced here---combined! We didn't lose any trees, but it seemed close. So take warning. Treat a Derecho just like a Hurricane and take a look at Wildman's recently posted check list.

Thing I ended up not having at the ready---a chain saw. . .with a sharp chain (really important)!

I would recommend people look at the Hurricane Checklist vs the Towboat Hurricane Checklist.

Derecho sounded a bit like Sirocco and they are related, along with Santa Ana's we have here. They're all straight-line potentially hurricane force winds, the apparent difference being where they originate and how they develop.

Sirocco winds carry dust from North Africa to Southern Europe. I experienced them in Spain, Italy and Greece. By the time they reached the Northern side of the Mediterranean the winds had slowed, but the dust was still there. So you get this dry, dusty wind coming off the sea.

Here in SOCAL we have Santa Ana winds, which are seriously dangerous during fire season. Hot dry winds pushing a fire -- don't be in the path.

On the prairies we call them "plough winds" and they happen quite frequently, maybe more often than tornadoes. They can and will cause a lot of damage to buildings and trees.