Dear Tom,
Why, so often, do lofty water towers survive tornadoes? Yes, they are heavy, but they have a high center of gravity open and exposed to the force of the storm.
John Hahn, Park Ridge
Dear John,
In the aftermath of a tornado, it is indeed surprising to see photographs of a large water tower standing unharmed in a field of debris.
National Weather Service meteorologist Brian Smith, who has conducted tornado research with Dr. T. Fujita and now participates in NWS storm assessment investigation of tornado disasters, says water towers can survive because of their streamlined shape.
Air flows smoothly around them, as opposed to houses, for example, which have eaves and sharp corners that cause turbulent air motion.
A streamlined water tower survived the F5 Barneveld, Wis., tornado in 1984 because air flowed sloomthly around it.
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Tom Skilling is chief meteorologist at WGN-TV. His weather forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.
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