Researcher promotes new rating system for winter's storms

PORTLAND, Maine -- Hurricanes and tornadoes are rated on a scale of 1 to 5. Why not snowstorms?

Gregory Zielinski, a researcher at the University of Maine, said the rating could be a quick and efficient way to warn the public of the severity of winter storms.

His study was published in the January edition of the Bulletin of the American Meteorological Society.

The proposed scale measures air pressure and duration of winter weather systems. A storm's speed is considered important because even an intense storm can have a relatively benign impact if it moves quickly.

The most ominous weather systems, both intense and slow moving, could earn a maximum 5.5 rating -- the first five for intensity, the second for longevity. That would send a simple message: Prepare for deep powder.

Zielinski's formula would allow meteorologists to recalculate a storm's rating every three hours as new data became available, Zielinski said.

Complex systems

But experts cautioned a numerical system for hurricanes might not work for winter storms. Winter weather is exceedingly complex, with characteristics that make adopting a simple classification scheme problematic.

"People need to know its limitations," said Elliot Abrams, the meteorologist who founded AccuWeather Inc. in State College, Pa. "With snow and ice, there are just so many different permutations."

The effects of a Category 5 hurricane are fairly predictable, Abrams noted. But a small winter storm can generate serious headaches if it deposits a thin layer of ice that coincides with the commuter rush hour.

Zielinski's system uses similar ratings as widely used scales for tornadoes and hurricanes. Tornadoes are rated on a scale developed by the late Tetsuya Theodore Fujita, a researcher from the University of Chicago. They are ranked from the least damaging, an F-0, to F-5, the most violent. Since tornadoes develop so rapidly, they are classified by intensity and wind speed only after they touch down.

Hurricanes with winds from 74 mph to 95 mph are Category 1, while the strongest tropical storms, with winds at 155 miles per hour and higher, are Category 5. Since wind speeds fluctuate rapidly, hurricane ratings sometimes change often.

Could be useful

The strongest blizzard in Zielinski's study was in December 2000. After forming in Colorado and moving through the Great Lakes, the storm produced near hurricane force winds along Maine's southern coast.

Some meteorologists said the new classification system might be useful, but previous ratings failed to catch on.

Under a scale developed in the 1970s, a light dusting was called a "nuisance," moderate snowfall required "plowing" and blizzards were labeled "crippling." But the terms never gained widespread acceptance.

Currently, the National Weather Service issues "winter storm advisories" when at least 5 inches of snow or any amount of ice is projected over a 24-hour period. A "winter storm warning" means forecasters expect at least 7 inches of snow or half an inch of ice.