The National Climatic Data Center is producing a new regional snowfall index; the Regional Snowfall Impact Scale (ReSIS). Like the Northeast Snowfall Impact Scale (NESIS), ReSIS uses snowfall and population to create an index that puts snowstorms and their societal impacts into historical perspective. However ReSIS only uses snowfall and population information within a particular region (collection of states) to calculate an index. NESIS uses snowfall and population information from the eastern two thirds of the United States and is therefore a quasi-national index. It is called Northeast" because some of the constants in the algorithm used to calculate NESIS are specifically calibrated to the northeast; a region with abundant snowfall and a large population. The constants in the ReSIS algorithms are specific to the region in which an index is being calculated. Therefore ReSIS is a true regional index.
While the Fujita and Saffir-Simpson Scales characterize tornadoes and hurricanes respectively, there is no widely used scale to classify snowstorms. The Northeast Snowfall Impact Scale (NESIS) developed by Paul Kocin and Louis Uccellini of the National Weather Service (Kocin and Uccellini, 2004) characterizes and ranks high-impact Northeast snowstorms. These storms have large areas of 10 inch snowfall accumulations and greater. NESIS has five categories: Extreme, Crippling, Major, Significant, and Notable. 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. For details on how NESIS scores are calculated at the National Climatic Data Center, see Squires and Lawrimore (2006).
Table 1: NESIS categories, their corresponding NESIS values, and a descriptive adjective:
| Category | NESIS Value | Description |
|---|---|---|
| 1 | 1—2.499 | Notable |
| 2 | 2.5—3.99 | Significant |
| 3 | 4—5.99 | Major |
| 4 | 6—9.99 | Crippling |
| 5 | 10.0+ | Extreme |
Table 2: Ranks 44 high-impact snowstorms that affected the Northeast urban corridor.
Click on hyperlinked dates for snowfall map. Sort by NESIS rank or storm date.
| Rank | Dates | NESIS | Category | Description |
|---|---|---|---|---|
| 44 | 25-26 January 1987 | 1.19 | 1 | Notable |
| 43 | 2-4 February 1995 | 1.43 | 1 | Notable |
| 42 | 22-23 February 1987 | 1.46 | 1 | Notable |
| 41 | 1-3 March 2009 | 1.59 | 1 | Notable |
| 40 | 18-19 March 1956 | 1.87 | 1 | Notable |
| 39 | 26-27 January 2011 (preliminary) | 2.17 | 1 | Notable |
| 38 | 31 March - 1 April 1997 | 2.29 | 1 | Notable |
| 37 | 30-31 December 2000 | 2.37 | 1 | Notable |
| 36 | 24-26 January 2000 | 2.52 | 2 | Significant |
| 35 | 15-18 March 2007 | 2.54 | 2 | Significant |
| 34 | 6-7 April 1982 | 3.35 | 2 | Significant |
| 33 | 5-8 February 1967 | 3.50 | 2 | Significant |
| 32 | 18-21 March 1958 | 3.51 | 2 | Significant |
| 31 | 8-10 February 1969 | 3.51 | 2 | Significant |
| 30 | 23-25 December 1966 | 3.81 | 2 | Significant |
| 29 | 18-21 December 2009 | 3.99 | 2 | Significant |
| 28 | 18-21 January 1961 | 4.04 | 3 | Major |
| 26 | 12-13 February 2006 | 4.10 | 3 | Major |
| 27 | 9-11 February 2010 | 4.10 | 3 | Major |
| 25 | 22-28 February 1969 | 4.29 | 3 | Major |
| 24 | 4-7 February 2010 | 4.38 | 3 | Major |
| 23 | 11-13 December 1960 | 4.53 | 3 | Major |
| 22 | 17-19 February 1979 | 4.77 | 3 | Major |
| 21 | 18-20 February 1972 | 4.77 | 3 | Major |
| 20 | 24-28 December 2010 (preliminary) | 4.92 | 3 | Major |
| 19 | 1-3 February 2011 (preliminary) | 5.30 | 3 | Major |
| 18 | 9-13 January 2011 (preliminary) | 5.31 | 3 | Major |
| 17 | 8-12 February 1994 | 5.39 | 3 | Major |
| 16 | 21-23 January 1987 | 5.40 | 3 | Major |
| 15 | 23-28 February 2010 | 5.46 | 3 | Major |
| 14 | 12-15 February 2007 | 5.63 | 3 | Major |
| 13 | 5-7 February 1978 | 5.78 | 3 | Major |
| 12 | 29-31 January 1966 | 5.93 | 3 | Major |
| 10 | 10-12 February 1983 | 6.25 | 4 | Crippling |
| 11 | 14-17 February 1958 | 6.25 | 4 | Crippling |
| 9 | 25-28 December 1969 | 6.29 | 4 | Crippling |
| 8 | 19-21 January 1978 | 6.53 | 4 | Crippling |
| 7 | 21-24 January 2005 | 6.80 | 4 | Crippling |
| 6 | 11-14 January 1964 | 6.91 | 4 | Crippling |
| 5 | 2-5 February 1961 | 7.06 | 4 | Crippling |
| 4 | 15-18 February 2003 | 7.50 | 4 | Crippling |
| 3 | 2-5 March 1960 | 8.77 | 4 | Crippling |
| 2 | 6-8 January 1996 | 11.78 | 5 | Extreme |
| 1 | 12-14 March 1993 | 13.20 | 5 | Extreme |
Kocin, P. J. and L. W. Uccellini, 2004: A Snowfall Impact Scale Derived From Northeast Storm Snowfall Distributions. Bull. Amer. Meteor. Soc., 85, 177-194
Squires, M. F. and J. H. Lawrimore, 2006: Development of an Operational Snowfall Impact Scale. 22nd IIPS, Atlanta, GA.
For all climate questions, please contact the National Climatic Data Center's Climate Services and Monitoring Division:
Climate Services and Monitoring Division
http://www.ncdc.noaa.gov/snow-and-ice/nesis.php
Regional Snowfall Impact Scale
