Development of regional snowfall indices

This paper describes a collaborative effort between NOAA's National Climatic Data Center and Rutgers University to develop regional snowfall indices for the U.S. on an operational basis. In 2005, NCDC began calculating the Northeast Snowfall Impact Scale (NESIS) operationally for large snowstorms affecting the northeast. The index is based on the spatial extent of the storm, the amount of snowfall, and the juxtaposition of population and snowfall. Including population information ties the index to societal impacts.

The goal of the current project is to develop NESIS-like indices for other regions of the country. The indices will be calculated in a similar fashion to NESIS, but our experience has led us to propose a change in the methodology. Different techniques are examined and a final algorithm is presented. The new indices require region-specific parameters and thresholds for the calculations. The paper discusses quality control issues, assumptions, and applicability of regional snowfall indices and how they may help explain the societal impacts of snowstorms. Indices are computed for the 50 largest storms in each of six regions in the eastern two-thirds of the nation to allow current storms to be put into a century-scale historical perspective. These indices are being produced experimentally for the 2009-2010 winter season.