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 41 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 |
---|---|---|---|---|
1 | 12-14 March 1993 | 13.20 | 5 | Extreme |
2 | 6-8 January 1996 | 11.78 | 5 | Extreme |
3 | 2-5 March 1960 | 8.77 | 4 | Crippling |
4 | 15-18 February 2003 | 7.50 | 4 | Crippling |
5 | 2-5 February 1961 | 7.06 | 4 | Crippling |
6 | 11-14 January 1964 | 6.91 | 4 | Crippling |
7 | 21-24 January 2005 | 6.80 | 4 | Crippling |
8 | 19-21 January 1978 | 6.53 | 4 | Crippling |
9 | 25-28 December 1969 | 6.29 | 4 | Crippling |
11 | 14-17 February 1958 | 6.25 | 4 | Crippling |
10 | 10-12 February 1983 | 6.25 | 4 | Crippling |
12 | 29-31 January 1966 | 5.93 | 3 | Major |
13 | 5-7 February 1978 | 5.78 | 3 | Major |
14 | 12-15 February 2007 | 5.63 | 3 | Major |
15 | 23-28 February 2010 | 5.46 | 3 | Major |
16 | 21-23 January 1987 | 5.40 | 3 | Major |
17 | 8-12 February 1994 | 5.39 | 3 | Major |
18 | 24-28 December 2010 (preliminary) | 4.92 | 3 | Major |
20 | 18-20 February 1972 | 4.77 | 3 | Major |
19 | 17-19 February 1979 | 4.77 | 3 | Major |
21 | 11-13 December 1960 | 4.53 | 3 | Major |
22 | 4-7 February 2010 | 4.38 | 3 | Major |
23 | 22-28 February 1969 | 4.29 | 3 | Major |
25 | 9-11 February 2010 | 4.10 | 3 | Major |
24 | 12-13 February 2006 | 4.10 | 3 | Major |
26 | 18-21 January 1961 | 4.04 | 3 | Major |
27 | 18-21 December 2009 | 3.99 | 2 | Significant |
28 | 23-25 December 1966 | 3.81 | 2 | Significant |
30 | 18-21 March 1958 | 3.51 | 2 | Significant |
29 | 8-10 February 1969 | 3.51 | 2 | Significant |
31 | 5-8 February 1967 | 3.50 | 2 | Significant |
32 | 6-7 April 1982 | 3.35 | 2 | Significant |
33 | 15-18 March 2007 | 2.54 | 2 | Significant |
34 | 24-26 January 2000 | 2.52 | 2 | Significant |
35 | 30-31 December 2000 | 2.37 | 1 | Notable |
36 | 31 March - 1 April 1997 | 2.29 | 1 | Notable |
37 | 18-19 March 1956 | 1.87 | 1 | Notable |
38 | 1-3 March 2009 | 1.59 | 1 | Notable |
39 | 22-23 February 1987 | 1.46 | 1 | Notable |
40 | 2-4 February 1995 | 1.43 | 1 | Notable |
41 | 25-26 January 1987 | 1.19 | 1 | Notable |
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.
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