Mesoscale Frequencies and Seasonal Snowfalls for Different Types of Lake Michigan Snow Storms

Abstract

Members of the Cloud Physics Laboratory, University of Chicago, have identified three different mesoscale organization patterns of lake-effect snow storms over Lake Michigan: multiple wind-parallel bands, single midlake bands, and single shoreline bands. For the 70 snowfall seasons ending with 1980/81, Braham and Dungey estimated that lake-effect snows contributed 8% of the total snowfall along the west shore of the lake, and 39% along the east shore. In the present study daily GOES satellite images and daily snowfall records are used to find the seasonal snowfall in four geographical area from each type of lake-effect storm and from nonlake-effect storms, for the snowfall seasons 1978/79 and 1979/80. Over the two seasons, 176 snowfall days were identified. Of these, 52% were nonlake-effect and 48% were lake-effect days. Of the 84 lake-effect days, 51% had wind-parallel bands, 22% had midlake bands, 2% had shoreline bands, and 25% had undetermined lake-effect cloud types. Along the west shore of the lake, lake-effect snows contributed 29% of the total snowfall, primarily from midlake bands. Along the east shore, lake-effect storms contributed 50% of the total snowfall. About half of the lake-effect contribution on the east shore was from wind-parallel bands, with most of the remainder from midlake bands and undetermined convective types. Although individual shoreline bands may yield locally heavy snowfalls, their contribution in 1978/79 and 1979/80 was very small, probably due to their low frequency of occurrence and the localized nature of their snowfall.