Thursday, February 11, 2016

100 m.p.h-plus winds in derecho?

Damage evidence suggests 100 m.p.h. gusts.

100 m.p.h-plus winds in derecho?


In an update posted today, the Storm Prediction Center noted that incredible derecho event at the end of June was by no means the most powerful or longest-lasting on record, but it did establish a few precedents.

For one thing, the storm cener said, this was "arguably the first derecho to capture widespread media attention."

It ripped into population centers along an ever-widening cone from Chicago to Atlantic City to Tidewater, Va.

Secondly, it set smashed June and July wind-gust standards are several observation sites.

It may be impossible to figure out, however, precisely how strong the winds became in places without official observations.

Jim Eberwine, retired from the National Weather Service, had an opportunity to view the damage firsthand during the early-morning hours of June 30 in his role as emergency chief in beautiful Absecon.

He said that while the highest observed gust in Absecon and Atlantic City was 74 m.p.h., and 81 in Tuckerton, he concluded "that winds easily gusted over 100 m.p.h., judging by the number of trees" and "the type of trees snapped or uprooted."

For his estimates, Eberwine was relying on a method pioneered by the late Theodore Fujita to determine wind speeds in tornadoes.

No wind instrument, assuming one would be in the path of a tornado, would survive powerful tornadic winds.

Fujita, using thousands of photographs, developed a system for inferring wind speeds based on damages. That's why the tornado scale, first developed in 1971, bears his name.

The scale has been modified in recent years, and now is known as the Enhanced Fujita scale.

Eberwine noted that the Fujita method can be applied to straight line winds -- such as those in a derecho -- as well as winds that travel in violent circles.

A footnote: As we mentioned Gary Szatkowski, the boss at the National Weahter Service in Mount Holly, posted a post-derecho report that talks about the warnings issue.

To get to the derecho part, skip to Page 6.



Inquirer Weather Columnist
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Everyone talks about the weather, and here we write about it.

When we’re around and conditions warrant, we’ll keep you updated about what’s coming, but we will do our best always to discuss weather and climate developments in context and remind you that nothing in the atmosphere happens in a vacuum.

Tony Wood has been writing about the atmosphere for The Inquirer for 26 years.

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