Development of a lake snow intensity index for the Tug Hill Plateau of New York State

Abstract:

Intense “lake effect” snowfall occurs to the lee of the Great Lakes when cold air travels over the much warmer lakes. This case study develops a Lake Snow Intensity (LSI) index based on circulation and thermodynamic patterns that are identified with the occurrence of heavy lake effect snowfall at a single location in the Tug Hill Plateau of New York State, which is located downwind of Lake Ontario and experiences particularly intense lake effect snowfall. Daily snowfall data for the period 1995-2019 are analyzed to identify 210 days when snowfall exceeded the NWS winter storm warning criterion of nine inches during a 24-hour period. North American Regional Reanalysis (NARR) data for circulation and thermodynamic variables related to wind speed and direction, as well as lower tropospheric stability and vapor content, are then analyzed using a principal components analysis (PCA) with a varimax rotation for a spatial domain that encompasses the Great Lakes region to both determine patterns that occur during heavy snow events and isolate centers of action that are most closely identified with the occurrence of these intense events. A HYSPLIT back trajectory analysis determines both fetch and residence time over Lake Ontario preceding each event and provides a measure of lake contributions to vapor flux and instability. Multiple regression analysis is then used to develop the LSI, which is based on the centers of action and back trajectories, where the LSI is proportional to daily snowfall amount.