Rare ‘derecho’ leaves swath of damage across Iowa

Midwest, USA
A power-punching, blustery storm that pummeled the Quad-City region Monday was a RARE severe weather event called a “derecho,” according to the National Weather Service. Derechos — from the Spanish word for “direct” or “straight ahead” — are most common in the late spring and summer, especially in the Corn Belt running from the upper Mississippi River valley to the Ohio River valley. The storms, which are rarer than tornadoes, are known for their longevity, incredibly high-sustained wind speeds and fast-moving nature. “We had a 60-mile-wide path of damage from Omaha through the Quad-Cities and on toward Chicago. Storms don’t usually stay that strong, that long. It’s like a 60-mile-wide train barreling across the state.” This is the first derecho to hit Iowa in two years. This one packed winds ranging from 65 to 95 mph. “We had one in the late 1990s that took a whole train off the tracks.” Conditions have to be very precise to create a derecho. There must be certain amounts of dry air aloft and moisture below. When conditions are right, the storm gears up and takes off at a high rate of speed in a “bow” shape. The front edge of the bow packs the heaviest winds, with less damaging winds on the outer edges. The storms are particularly dangerous because they appear quickly, often before sufficient warning can be given.