Steve Karnowski - Associated Press
Friday, August 17, 2001
Minneapolis --- When the icy blasts of winter return to North America, those fearsome wind chill numbers won't sound quite as ominous as before. The National Weather Service and its Canadian counterpart are switching to a tamer formula for computing wind chill, one they say will provide more accurate information. The combination of bitter cold and biting wind that generated a wind chill index of 70 below last winter, for example, will work out to 44 below with the new formula.
The new numbers will give people who dare to venture out in such weather a more realistic guide to how they should bundle up, since they'll be based on how the wind actually feels to exposed human skin. The old wind chill charts were based on research in Antarctica in 1945, when scientists measured how wind affected the rate at which water froze. The new research studied how wind and cold really affect people. Randall Osczevski, an environmental physicist with the Department of National Defense in Canada, directed tests in which a dozen volunteers with temperature sensors attached to their faces were blasted in a wind tunnel.
"The new wind chill index has been clinically tested," said Mark Tew, a National Weather Service meteorologist in Silver Spring, Md., who chaired a joint U.S.-Canadian task force that developed the new formula. One of the key differences between the old and the new indexes is that, instead of using wind speed as measured at 33 feet above the ground, meteorologists now will use readings taken at 5 feet. "Face height," Tew called it. The new formula also takes advantage of advances in science, technology and computers, he said. The chart also highlights the danger of frostbite, which can occur within 15 minutes when the wind chill index is 18 below zero, Tew said. The old system simply showed graduated zones of danger.
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