The Woodward News

Local News

July 28, 2013

Derechos are not uncommon

(Continued)

Woodward, Okla. — DIFFERENT THAN OTHER WIND EVENTS

Barnes noted that derechos are "included in a family of downburst clusters," with a downburst referring to a strong downward current of air usually associated with thunderstorms.

Lehenbauer said "it can get kind of confusing sometimes when you're talking about downbursts, microbursts, and derechos.  And I think last year we even had a heat burst in the area, which is not even storm related, but all of a sudden warm air falls out of the atmosphere and you can get winds from that which can cause damage.  They're all wind, but just caused by different things."

Both Barnes and Lehenbauer said that the biggest difference between a derecho and other wind events is the scope of the associated wind.

"It's a little bit different than a normal downburst or a microburst.  Those are high winds as well but they're in isolated pockets that go away pretty quickly," Lehenbauer said.  "With a derecho there are sustained winds.  You may get hit with that gust front, but behind that there's heavy winds that usually last for several hours."

Barnes used distance, rather than time to describe the scope of a derecho.

"A derecho is caused by a big cluster of storms and can produce damaging straight-line winds over hundreds of miles and is sometimes more than 100-miles wide," he said.  "That's the main difference from other wind events, because if you're talking about just one storm, then it may just cause damage over a 5-mile or 10-mile area."

AN UNFAMILIAR TERM

If you find derecho to be an unfamiliar term, that's because it is not often used when releasing weather warnings to the public.

There are many reasons why meteorologists don't use the derecho term when warning the public about these wind events.

One is simply because a storm might not be classified as a derecho until after the storm system has already passed, such as with the recent storm that did damage in Northeast Oklahoma this past week.  

Since a derecho involves strong winds that are sustained for hundreds of miles, the storm must first cross hundreds of miles before it can be deemed a derecho.  So there is a lot of analysis and data collection involved before meteorologists will label a storm as a derecho.

"It's more of a term that's used after the fact or a term used by meteorologists," Lehenbauer said.

He said that's because is "more of a technical term. So normally you would not hear the word used in news broadcasts.  Instead you'll hear terms like bow echo or heavy winds along a front."

Also, since derechos are often associated with thunderstorms, the National Weather Service will usually issue a broader thunderstorm warning and then include strong wind advisories within that warning.

"When we expect real strong straight-line winds, if you'll pay close attention to National Weather Service storm warnings, you'll hear specifics about wind speeds and the precautions you need to take," Barnes said.

Both he and Lehenbauer said the precautions are similar for any other strong wind events.

"With a derecho, winds are expected to be around 70 mph to 80 mph, so you'll want to be in the in the interior of your home away from any windows and not be driving around," Barnes said.

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