OTTUMWA —
The widespread damage to the Washington D.C. area last week and the continuing power outages there were the result of a derecho, a powerful and long-lasting complex of storms.
Can they happen in southeast Iowa? The answer is an unequivocal yes.
A derecho (deh-REY-cho) packs a wallop because it holds unusually powerful thunderstorms together over long distances. It's not uncommon for them to travel across several states and some can last almost 24 hours as they plow across the country.
In order to be classified as a derecho, the storms must have wind gusts of more than 57 mph "at most points along the derecho path," according to the National Oceanographic and Atmospheric Administration (NOAA). The powerful winds are produced by downbursts within the storms.
Most derechos take place during May, June and July, with a dramatic dropoff for the rest of the year. That's not surprising, since those are the main months for thunderstorms. And most of Iowa can expect a derecho to hit about once every other year.
But more frequent events can take place. Southeast Iowa was hit by three derechos in 2005 alone and a fourth clipped the area. NOAA records show storms on June 4, 2005 knocked down trees and utility poles in Centerville, took down large limbs in Mahaska County and caused hundreds of damage reports from Texas through Wisconsin.
A second derecho four days later caused hail and 60-70 mph winds in Ottumwa and ravaged the Bloomfield town square.
The final derecho of 2005 for the area was in September. The main damage came from wind that time, with reports stretching from Iowa's northwest corner into central Illinois.
Last week's storms are instructive. Forecasters said there was a risk of severe weather for the D.C. area, but didn't predict anything on the scale of what happened. Warnings came only after the storms started.
The lesson: Pay attention to forecasts throughout the day. They can change, and those changes can have life-or-death implications.
Southeast Iowa
Related Photos
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Derecho frequency map
Derechos like Washington saw have happened here
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