Examining the land-lake-atmosphere interactions of the May 5, 2003 severe weather event over southwest Michigan

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Tuesday, 4 February 2014
Hall C3 (The Georgia World Congress Center )
David M. Wright, University of Michigan, Ann Arbor, MI; and D. J. Posselt and G. Mann

Hydrology in the Great Lakes region is complex and not fully understood, due in large part to the land-lake-atmosphere interactions and the mesoscale features associated with these interactions. These features, such as lake breezes and lake effect snow, play an important role in the distribution of water in the region. During the late spring and summer months, the difference in temperature between the relatively colder lake surface and the warmer atmosphere typically results in a stabilization of the lower boundary layer. The temperature contrast between the lake surface and the land mass also allows for lake breezes to form in a manner similar to how sea breezes form in other coastal areas. While the majority of these features have been studied and are well documented, there are still several interactions between the lake surface and surrounding environments that have been observed, but are not fully understood. This creates a knowledge gap for weather forecasters in the region, and contributes to uncertainty in climate change assessments of regional hydrology.

The case examined in this study occurred in early May 2003, when a nearly stationary line of cumulus clouds formed several kilometers inland from Lake Michigan over southwest Michigan. These clouds eventually developed into a line of severe thunderstorms several kilometers inland from the lake, resulting in a rain shadow along the coast. The thermodynamic and dynamic structure of this system is explored through high-resolution Weather Research and Forecasting Model (WRF) simulations. These simulations examine the mechanisms for the formation of the severe weather, as well as the sensitivity of the system to environmental and lake properties. Identifying these mechanisms is key for weather forecasters in the region to be able to predict the potential of severe weather events. Understanding this fine-scale feature could also be important for evaluating future climate scenarios, as existing climate models may not accurately represent the land-lake-atmosphere interaction in the Great Lakes region.