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Lake Effect Storms Lake Effect Storm Types • Wind/Shear Parallel Bands • Shore Parallel Bands – Shore based – Midlake • Mesoscale Vortex Lake Superior Lake Effect Lake Ontario Lake Effects Lake Michigan Shore Parallel Band Lake Michigan Wind/Shear Parallel Band 10 and 13 January, 1998 Visible Satellite Loop • Cloud rolls over water • Spectacular Cloud streets over land • Effect of lake shoreline • Gravity waves perpendicular to flow 1704 UTC - 1748UTC Characteristics of Wind Parallel vs. Shore Parallel Bands Convective Boundary Layer Roll Convection Instabilities Driving CBL Organization Growth of Planetary Boundary Layer Across Lake Shore Parallel Bands – Wind blows roughly parallel to major axis of lake – Air warms from heat flux from water creating a strong land-water air temperature contrast – Land Breeze is created forcing a land breeze front and meso-beta scale convergence – Meso-beta scale lifting of air to as high as 4 km AGL (compared to 1 km AGL for wind parallel bands) along land breeze front (s) – Land breeze fronts usually combine into single convergence line • Parallel to shoreline of lake • Pushed to downwind shoreline when winds are not completely parallel to shoreline • Down center of lake when winds are exactly parallel to shoreline of lake Shore Parallel Bands • Most intense snows of all the different lake-effect snow types, because: – Concentrates all of the absorbed moisture and heat along a single narrow band – Mesoscale lifting deepens the system to several kilometers allowing precipitation processes to be more efficient • Colder than –20 C • Deeper layer Bergeron – Findeisen Process – Bands extend off shore and drop massive amounts of snow over small region • Buffalo, NY (Lake Erie, WSW wind) • Gary, Indiana (Lake Michigan, Northerly wind) Predicting Wind Parallel Lake Effect Storms • Lake temperature minus 850 mb temperature >13C • Wind fetch >100 km • Wind speed moderate to high, i.e. >10 m/s Predicting Shore Parallel Lake Effect Storms • Wind nearly parallel to long axis of lake • Lake temperature minus 850 mb temperature >13C (can occur with less temperature contrast) • Wind speed light to high, i.e. > 5 m/s