Abstract
As the mesoscale dynamics of lake-effect snow (LES) are becoming better understood, recent and ongoing research is beginning to focus on the large-scale environments conducive to LES. Synoptic-scale composites are constructed for Lake Michigan and Lake Superior LES events by employing an LES case repository for these regions within the U.S. North American Regional Reanalysis (NARR) data for each LES event were used to construct synoptic maps of dominant LES patterns for each lake. These maps were formulated using a previously implemented composite technique that blends principal component analysis with a k-means cluster analysis. A sample case from each resulting cluster was also selected and simulated using the Advanced Weather Research and Forecast model to obtain an example mesoscale depiction of the LES environment. The study revealed four synoptic setups for Lake Michigan and three for Lake Superior whose primary differences were discrepancies in a surface pressure dipole structure previously linked with Great Lakes LES. These subtle synoptic-scale differences suggested that while overall LES impacts were driven more by the mesoscale conditions for these lakes, synoptic-scale conditions still provided important insight into the character of LES forcing mechanisms, primarily the steering flow and air–lake thermodynamics.
Highlights
The North American Great Lakes have multiple effects on the weather and climate of the neighboring landscape [1,2,3,4,5]
The upperlevel trough deepened over the 24 h, attaining a positive tilt that shifted towards a neutral tilt with associated differential cyclonic vorticity advection (DCVA)
(800 m difference), and suppressed convection, likely a result of a colder lake temperatures and subsequently lower energy fluxes. These results show the importance of the synoptic-scale in establishing basic structures but that the mesoscale environment is most important for final lake effect snow (LES) development
Summary
The North American Great Lakes have multiple effects on the weather and climate of the neighboring landscape [1,2,3,4,5]. The destabilization of continental polar air masses traversing over the lakes via massive vertical heat and moisture fluxes result in severe lakeeffect snow (LES) storms that produces copious amounts of winter precipitation downwind of the lakes [7,8,9,10]. This area downwind of the lakes affected by LES is known as the ‘snow belt’ region as annual snowfall maps reveal that these elongated areas receive substantially higher snowfall compared to areas more inland, with up to 50% of their annual snowfall coming from LES (Figure 1). The unique shape of these snow belts is a consequence of the elongation of snow bands that tend to form during LES events
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