Snowstorm scale rates intensity New measure to compare, not forecast, snows in Northeast

WASHINGTON – Scientists are launching a new way of rating snowstorms, a scale with five categories of intensity that won’t be used as a warning tool but will allow storms to be compared with others.

The Northeast Snowfall Impact Scale will be used this winter to rate snowstorms in the Northeast immediately after they strike, the National Oceanic and Atmospheric Administration said Monday.

Like the Saffir-Simpson scale for hurricanes and the Fujita scale for tornadoes, the new scale has five levels of intensity.

But rather than being based only on weather factors such as wind or storm surge, it also includes the impact on people.

Unlike the hurricane scale, which is used in forecasts to warn specific areas of the need for evacuation, the purpose of the snowstorm scale is to assess the impact of the storm right after it occurs.

There are no immediate plans to try to use it as a warning tool, said Jay Lawrimore of the National Climatic Data Center, which is responsible for calculating the scale.

The scale ranks storms as 1, notable; 2, significant; 3, major; 4, crippling and 5, extreme.

Developed by Paul Kocin, a winter storms expert at the Weather Channel, and Louis Uccellini, director of the NOAA National Centers for Environmental Prediction in Camp Springs, Md., the rating factors in the number of inches of snow, and the land area and number of people affected.

The scale was developed for the Northeast because of the economic and transportation impact such storms have on the whole country.

The rating system comes two years after another 1-to-5 winter storm ranking was proposed by Gregory A. Zielinski of the University of Maine.

Zielinski’s system focuses on the intensity of the storm and its speed of movement as a way to assist forecasters in warning the public. It does not include a measure of the population likely to be affected by the storm.

Lawrimore said there are plans to extend the scale to other regions, but that needs further study because winter storms develop in different ways in various parts of the country.

Two Northeastern storms in recent years fall into the extreme category under this scale.

One was the storm of March 12-14, 1993, in which nearly 67 million people were inundated with 10 inches of snow or more, almost 20 million were affected by 20 inches of snow, and 1.8 million had 30 inches or more of snow.

The other, Jan. 6-8, 1996, affected a somewhat smaller land area but dumped 10 inches of snow on 66 million people, 20 inches on nearly 40 million and 30 inches on 5.1 million people.

On this scale, the infamous Blizzard of 1888 that staggered New York City on March 11-14 of that year would have ranked in category 4, crippling, as would the Blizzard of 1899 that affected coastal areas from the Carolinas to Maine in mid-February.