Photograph by Whitney Curtis, Getty Images
A man surveys the debris of the home where his mother-in-law died in Harrisburg, Illinois. The wrecked dwelling was hit by one of dozens of tornadoes that sliced through the U.S. Midwest and South last week. At least 39 people in five states lost their lives.
The 180 mile-per-hour (290 kilometer-per-hour) twister, about 275 yards (250 meters) wide, that touched down in Harrisburg was rated an F-4 tornado on the five-level enhanced Fujita scale of intensity. The power it packed was the equivalent of 160,000 kilowatt-hours, says Dr. Joseph Schaefer, director emeritus of the Storm Prediction Center, part of the U.S. National Oceanic and Atmospheric Administration, based in Norman, Oklahoma. That's the amount used by 5,000 average U.S. homes over the course of a day.
And tornadoes can generate even more destructive energy. The unusually monstrous F-5 funnel that devastated Joplin, Missouri, on May 22, 2011, may have exceeded 200 mph (320 km/hour). Its energy could be estimated at double that of the tornado at Harrisburg, says Schaefer.
A tornado's intensity comes from packing its wallop into a small space. The average tornado over the past 20 years has been only 100 yards (91 meters) wide, says Greg Carbin, the storm center's warning coordination meteorologist. An example, Carbin says, is a tornado that touched down outside Tampico, Texas, in 1999. Nobody was hurt and little damage was done.
In contrast, a typical hurricane is 300 miles (483 km) across.
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