Numerical Simulation of Land-Breeze-Induced Snowbands Along the Western Shore of Lake Michigan

Abstract

Case studies are presented which describe a type of lake-effect snowband which forms along the western shore of Lake Michigan when a cold anticyclone to the north sets up an easterly gradient over the lake. Numerical simulations indicate that the snowband coincides with a narrow band of upward motion which results from the convergence of easterly winds over the lake and north to northwesterly winds over land. The northerly winds are part of a land breeze circulation which forms when cold air is heated by the relatively warm lake surface. Initial data for model simulations are obtained by objective analysis of upper-air data from the eight upper-air stations closest to Lake Michigan at six levels in the lower troposphere. Model results show that a pool of cold air over the lake up to about 850 mb favors rapid growth of the planetary boundary layer over the western half of the lake, and that latent heat release plays an important role in intensifying the land breeze circulation.