Recent Advances in Our Understanding of Extreme Snowfalls Produced by the Interaction of Lake-Effect Systems with Orography

Orography has a dramatic influence on lake-, sea-, and ocean-effect storms (hereafter simply lake effect) from the modest relief downstream of the Laurentian Great Lakes to the imposing mountains of Japan’s Honshu and Hokkaido Islands. Lake-effect snowstorms on the Tug Hill Plateau east of Lake Ontario are amongst the most intense in the world, while prolific snowfall in the mountains of Honshu and Hokkaido Islands during the Asian winter monsoon produces some of the deepest seasonal snowpacks measured.

This presentation describes recent advances in our understanding of lake-effect systems and their modification by orography. It draws on findings derived from the Ontario Winter Lake-effect Systems (OWLeS) field campaign, radar-based climatologies from the Tug Hill Plateau of upstate New York and the Hokuriku region of Japan, space-borne remote sensing, real-data mesoscale modeling, and idealized cloud modeling. These multiple lines of inquiry highlight the importance of coastline geometry in organizing lake-effect systems and illustrate how the inland penetration and orographic enhancement of lake-effect precipitation is modified by the characteristics of the incident flow, mode of the lake-effect system, and shape and size of the downstream terrain. The implications of these findings for existing conceptual models of lake-effect systems and their interaction with orography, operational forecasting, and our understanding of extreme snowfall produced by lake-effect and orographic processes will be examined.