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Michael T. Shields, Robert M. Rauber, and Mohan K. Ramamurthy

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.

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Mohan K. Ramamurthy, Robert M. Rauber, Brian P. Collins, Michael T. Shields, Patrick C. Kennedy, and Wallace L. Clark

To obtain a better understanding of the role of synoptic-scale disturbances in organizing mesoscale precipitation in the midwestern United States during the winter season, and to address scientific issues regarding mesoscale dynamics of winter storms, the University of Illinois Winter Precipitation Program was conducted over a period of three winters between 1988 and 1990. The observing systems included a 10-cm wavelength meteorological Doppler radar operated by the Illinois State Water Survey, the Flatland 6-m wind profiler operated by the NOAA Aeronomy Laboratory, and an NCAR Cross-chain Loran Atmospheric Sounding System. In all, 26 storms were observed during the 3-year period. The associated precipitation ranged from highly convective storms in the warm sector to stratified clouds containing organized banded structure within the occlusion. The principle dynamical mechanisms at work often varied widely from one storm to another and sometimes within a storm. This article describes the goals and objectives of the project, as well as a few selected observations and some preliminary findings from the data gathered.

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