WRAL WeatherCenter Blog

Another Rating System is Born...

Posted February 6, 2006 11:41 a.m. EST

We're all familiar with the Saffir-Simpson scale for hurricanes, ranging from category 1 to category 5 monster storms, and the conceptual,ly similar Fujita scale for tornado intensity, which ranges (in practical terms) from F0 on the low end to F5 for extremely violent storms. Until now, there hasn't been anything similar devised that quantifies the intensity and impact of wintry weather, but NOAA, the NWS and the National Climatic Data Center (NCDC) announced last week the development and implementation of the Northeast Snowfall Impact Scale (NESIS) which combines snowfall amounts with a measure of population affected to rate snowstorms, on a five step scale ranging from "notable" at Category 1 through "significant," "major" and "crippling" to "extreme" at Category 5. Unlike the other scales, which are used both in forecasts (especially for hurricanes) and a post-storm analysis mode, the NESIS is intended for post-analysis in climatological ranking and record-keeping. An ongoing project at NCDC will go back and assign categories to all northeast U.S. snowstorms since the late 1800s. Initial rating of snowstorms from recent decades has identified two Extreme Category 5 storms, the "Storm of the Century" from March 1993 that left 50 inches of snow on Mt Mitchell, and another extreme storm from January 1996, while the very intense, from our perspective, storm of January 24-26 2000 only rated a Category 2.