Dynamical Forcing and Mesoscale Organization of Precipitation Bands in a Midwest Winter Cyclonic Storm

Abstract

A winter snowstorm developed on 10?11 February 1988 over the midwestern United States and produced several inches of snowfall locally over east-central Illinois. Analysis of the mesoscale organization of the storm revealed the presence of complex banded structure throughout its 17-h evolution. Three distinct types of mesoscale precipitation bands were identified during the course of the storm using a 10-cm Doppler radar as part of the University of Illinois Winter Precipitation Program. The bands had different orientations, directions of movement, relationships to synoptic-scale frontal zones, and mechanisms for development. The mesoscale organization of this storm system is reviewed. Mesoscale, synoptic-scale, and Doppler analyses of the storm structure are presented. The role of boundary-layer convergence, conditional symmetric instability, and frontogenetical forcing in the formation and maintenance of the different mesoscale precipitation bands is discussed.