(FORTUNE Magazine) – Kansans, rejoice: The tornado season, which just ended, was a quiet one. Preliminary data show 576 twisters during the past six months, well below the average of 939 storms for the prior three seasons. That's good news, because as any Wizard of Oz fan knows, it's not just a tornado's winds that pose a threat: Cyclones suck up debris, which can be dangerous when it falls to earth. In the past, twisters have flung an airplane wing, a carton of deer hides, and a soiled wedding dress. Today cartons of medical waste, chemicals, and other hazardous materials are equally vulnerable.

That's why John T. Snow, a professor of meteorology at the University of Oklahoma, has helped develop a model to predict where storm-borne detritus will fall. Over the past six years Snow has collected data from residents in twister-prone regions who have carefully recorded the date, time, and location of anything unusual that falls from the sky after a storm. (Snow's favorite far-flung item is a jacket from a bowling team called the Gators.) The findings: Items weighing more than one pound rarely travel more than 50 miles. The lightest debris--such as paper--sails much farther; the longest trip was 210 miles. And most of the litter lands to the left of the storm's direction.

Snow now uses the model to advise companies on emergency planning, but hopes to refine the data in the future. "The model needs a lot more work," he says. "But it's better than just saying it went off to the Land of Oz."

--Susan Q. Stranahan