Dear Tom,
The air pressure is lower in a tornado, but by how much?
Susan Bosserman
Dear Susan,
In the absence of actual measurements, atmospheric scientists speculated that a powerful tornado might generate an air-pressure reduction of 1.5 inches of mercury–the equivalent of one-twentieth of normal air pressure at sea level (30 inches of mercury).
That all changed on June 24, 2003, in Manchester, S.D., when electrical engineer Tim Samaras, working in cooperation with The National Geographic Society, the National Weather Service and Applied Research Associates, Inc., managed to place a specially designed pressure probe into the path of an F4 tornado (winds 207-260 m.p.h.).
Incredibly, the probe recorded an air pressure drop of 2.95 inches in 26 seconds.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
