The interaction of mesoscale convective systems with the Great Lakes during BAMEX

During the Bow Echo and Mesoscale Vortex Experiment (BAMEX) in the late spring and early summer of 2003 there were several observed instances of interactions between the Great Lakes and mesoscale convective systems (MCSs). One case from 11-13 June involved a long-lived mesoscale convective vortex MCV) that formed in Oklahoma and tracked northeastward to Lake Erie. As this MCV approached Lake Erie it acquired frontal structure and began to look like a classic Norwegian cyclone. The frontal structure resulted from the interaction of the cyclonic circulation around the MCV with a quasi stationary pre-existing baroclinic zone arising from land-water temperature contrasts near the southern end of the Great Lakes.

A second case from 4 July involved a bowing squall line/MCS that organized over IA/MN around 0600 UTC and reached the western shore of Lake Michigan AT 1200 UTC. As the squall line crossed the chilly waters of Lake Michigan, a slight strengthening was observed (based upon ASOS time series, damage reports, and radar reflectivity imagery). The squall line held together as it moved ESE across lower MI toward northwestern OH and Lake Erie by 1900 UTC. As the squall line crossed western Lake Erie, the portion of the line over the lake weakened rapidly. The southern part of the line appeared to lay down a weak outflow boundary over parts of northern IL/IN that may have served as a possible focus for new convection that erupted in the late afternoon hours of 4 July.

The purpose of this presentation is to illustrate the interaction of these MCSs with the Great Lakes through analysis of radar imagery and surface observations. The radar imagery is especially helpful in delineating variations in convective mode and intensity as MCSs approach and cross the Great Lakes. Scientific opportunities and forecast challenges will also be discussed. Results will be on http://www.atmos.albany.edu/student/tomjr/rad05.html as they become available.