Derecho

Reported June 2006

NORMAN, Okla. (Ivanhoe Broadcast News) -- A derecho is a weather term meteorologists admit most people don't know about. But in this past year of unpredictable weather, it's worth learning about.

"It caught it up just right and then just rolled it -- just it rolled along."

What warning coordination meteorologist Dan McCarthy's talking about is a huge Doppler radar that was whipped around by a storm called a derecho. The staff at the NOAA National Severe Storms Laboratory got an up close and personal look at what damage a derecho can do.

"The derecho lasts for hundreds of miles as it moves across the ground, causing damaging winds of up to 80 to 100 miles per hour," McCarthy, of the NOAA Storm Prediction Center in Norman, Oklahoma, tells Ivanhoe.

A derecho is a widespread and straight-lined windstorm that often has a band of rapidly moving thunderstorms associated with it. These conditions are ripe for generating multiple tornadoes that can cause severe damage. "Some derechos can down homes ... Some derechos can roll over mobile homes ... Many derechos take roofs and take fences down. So they can be just as destructive as tornadoes."

The term derecho was coined by Doctor Gustavus Hinrichs, a physics professor. It's a Spanish word that means direct or straight ahead, while tornado is thought to be from the Spanish word tornar, which means to turn.

Meteorologists usually issue a severe thunderstorm watch when they see an approaching derecho.

McCarthy says, "If we recognize the situation that can go for 100s of miles, we will add the particularly dangerous situation wording to it."

If you get that warning, move your family away from windows into a safe place and wait until the storm is over.

Derechos are more common in spring and early summer and occur more frequently in the Corn Belt and along the Southern Plains, but they have been reported as far north as Michigan, as far south as Florida, as far west as Texas, and as far east as Maine.

Click here to Go Inside This Science or contact:

National Centers for Environmental Prediction
Storm Prediction Center
1313 Halley Circle
Norman, OK
spc.feedback@noaa.gov

For more information about the science behind weather forecasting, contact:

The American Meteorological Society
Boston, MA 02108-3693
(617) 227-2425
http://www.ametsoc.org

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