Warm-season MCS initiation and development influenced by land/lake thermodynamic contrasts near the Great Lakes

One of the primary considerations for the influence of the Great Lakes on MCS development is the (potential) temperature gradient close to the surface across the land/lake boundary. This mesoscale, thermodynamic boundary is usually formed around a lake due to differential heating of the land and lake surfaces, and can be maximized in the warm season. An intense land/lake boundary can interact with surrounding environmental features to help induce convection and MCS formation near the lake. This study will focus on a radar climatology and selected case studies highlighting the different pathways for MCS initiation and development near the Great Lakes.

The climatology will elucidate the most favorable land/lake conditions, positions, synoptic conditions, and times of year for MCS initiation near the Great Lakes. Using these results, case studies highlighting the most relevant factors for MCS generation will be discussed, including the land-surface/lake-surface temperature contrast, the depth of the over-lake cold pool, and the direction of low-level wind direction and wind shear. Preliminary results suggest that, upstream of the lake, sufficient forcing for ascent and MCS development may be attained in association with surface convergence between the end of the lake's “cold dome” and any pre-existing over-land cold pools. Downstream, isolated convection moving off the cool lake can have an “apparent” cold pool in place, which can lead to MCS (re)development more rapidly into the optimal or mature stages (as discussed in Rotunno et al. 1988).