Lake-ICE observations during wintertime cold air outbreaks over the Great Lakes Region

The wintertime impacts of the Great Lakes on a developing low pressure system that moved eastward north of the region is examined. The event occurred over a two day period of the Lake-Induced Convection Experiment (Lake-ICE) – from 12-13 January 1998. A network of six Cross-Chain Loran Atmospheric Sounding Systems (CLASS) were situated as part of the Lake-ICE facilities throughout Central and Northeastern Ontario and western Quebec. The event provided an excellent opportunity to observe (for the first time) the meso-a scale (aggregate) effects of the Great Lakes on the evolution of the planetary boundary layer in winter.

The low entered the western Great Lakes region with the center located several hundred kilometers to the north of Lake Superior. As the low slowed its eastward progress, it deepened 10 hPa over a period of 12 h, and moved southeastward several hundred kilometers to a position along the north shore of Lake Huron before retreating northward again as it accelerated eastward. The low center tracked directly through the CLASS observing network.

Three hourly observations from the CLASS sites and model output from a series of high-resolution with-lake and no-lake numerical simulations conducted using the Penn State/National Center for Atmospheric Research mesoscale model show how the Great Lakes were responsible for heating, moistening, and destabilizing the boundary layer in the warm sector of the cyclone as it moved eastward north of the region. These boundary layer effects were thus responsible for strengthening both the cold and the warm fronts, as evidenced by enhanced convective precipitation, and ultimately strengthening the cyclone and causing it to shift temporarily southward.