January 1, 2007 — Those who live in the Northeaster United States will be able to plan ahead for major storms thanks to a new ranking scale that predicts not only how many inches of snow will fall, but also how long delays will last. The Northeast Snowfall Impact Scale, or NESIS, ranks storms by size, amount of snowfall and number of people affected. Meteorologists will assess the storm's impact today, compare it with past storms, and then assign it one of five categories: Notable, Significant, Major, Crippling or Extreme.
CAMP SPRINGS, Md. -- When a winter storm hits, so do delays and headaches. Do you stockpile candles and canned goods or prepare the ice scraper and expect a difficult drive to work tomorrow?
Snowstorm warnings predict how many inches to expect, but don't say how long delays will last. Now, a new system ranks a storm's strength and helps predict when things will be back to normal.
Developed by meteorologists, the Northeast Snowfall Impact Scale, or NESIS, ranks storms by size, amount of snowfall and number of people affected.
"It boils down to how much snow falls on the population," Meteorologist Louis Uccellini, Ph.D., tells Ivanhoe.
Researchers like Dr. Uccellini at the National Centers for Environmental Prediction (NOAA) in Camp Springs, Maryland, assess the storm's impact today, compare it with past storms, and then assign it one of five categories: Notable, Significant, Major, Crippling or Extreme.
"Relaying that this is going to be a category three, four or five storm, we tell you that this is similar to the 'Blizzard of 1996' or the 'Superstorm of 1993,' you will immediately know that this is going to be a storm of major proportions," Dr. Uccellini says. Those were the only two storms in the past century that rated category five or extreme -- the Blizzard of January 1996 dumped 17 to 30 inches of snow in every city from Washington, D.C., to Boston.
The northeast is the first region to use NESIS because it is so heavily populated. The new rating system is used after snow falls, but it could be used in forecasts to help warn of major traffic, school and airport delays -- dealing with the storms, one snowflake at a time.
The American Meteorological Society contributed to the information contained in the TV portion of this report.
BACKGROUND: Scientists at the National Oceanic and Atmospheric Administration (NOAA) have devised a new, easy-to-understand scale to categorize major snowstorms after they hit the Northeast. The Northeast Snowfall Impact Scale, or NESIS, quickly calculates the impact of a powerful snowstorm soon after it strikes, ranking it similar to methods used to categorize the strength of tornadoes or hurricanes. While winds are used to measure a hurricane's intensity, NESIS will rank the severity of a Northeast snowstorm based on snowfall amounts and the population of the affected areas, then compare it with past storms (dating back to as early as the late 1800s) before assigning it a category: Notable, Significant, Major, Crippling or Extreme.
HOW STORMS DEVELOP: Storm clouds form as moisture evaporates from the earth into the atmosphere, where the droplets congregate and jostle against each other. The air cools rapidly as it rises and the water vapor "condenses" into liquid drops, forming clouds. The process continues: more and more water vapor turns into liquid, and the moist air warms even more and rises higher and higher.
Winter storms are those where, instead of rain, the dominant form of precipitation is snow, sleet or freezing rain; if large amounts of snow fall, it is considered a snowstorm. Add strong winds and "whiteout" conditions, and it might be considered a blizzard. Snow is less dense than liquid water, so the same amount of water that would amount to less than an inch of rain could produce as much as eight inches of snow. Just two inches of snow is sufficient to create traffic disruptions, particularly in cities where snowfall is uncommon. If more than 12 inches of snow accumulate, the weight can cave in the roofs of homes and cause power loss.
THE ICE STORM: Freezing rain storms are especially dangerous. They occur when a layer of warm air hovers over a region where the ground temperature is below freezing. If it results in widespread icing of plants, structures, and roads, it is deemed an ice storm. Even an ice storm with an accumulation of half an inch can paralyze a region. Driving is extremely hazardous, telephone and power lines can be damaged, and in rural areas, crops can be damaged.
The American Meteorological Society contributed to the information contained in the TV portion of this report.
Note: This story and accompanying video were originally produced for the American Institute of Physics series Discoveries and Breakthroughs in Science by Ivanhoe Broadcast News and are protected by copyright law. All rights reserved.
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