There are Cat 3 Hurricanes & EF-3 Tornadoes, But Do Winter Storms Get Categories Too???


Many people are aware of the Enhanced Fujita (EF) Scale for tornadoes.  Most also know about the Saffir-Simpson Hurricane Wind Scale.  However there is also a rating scale for Winter Storms that fewer people know about. In 2004, Paul Kocin and Louis Uccellini from the National Weather Service (Kocin and Uccellini, 2004) developed the Northeast Snowfall Impact Scale (NESIS).    Below is a description from the National Climate Data Center (NCDC) website for NESIS:

“The index differs from other meteorological indices in that it uses population information in addition to meteorological measurements. Thus NESIS gives an indication of a storm’s societal impacts. This scale was developed because of the impact Northeast snowstorms can have on the rest of the country in terms of transportation and economic impact.

NESIS scores are a function of the area affected by the snowstorm, the amount of snow, and the number of people living in the path of the storm. The diagram below illustrates how NESIS values are calculated within a geographical information system (GIS). The aerial distribution of snowfall and population information are combined in an equation that calculates a NESIS score which varies from around one for smaller storms to over ten for extreme storms. The raw score is then converted into one of the five NESIS categories. The largest NESIS values result from storms producing heavy snowfall over large areas that include major metropolitan centers. Continue reading