Lake Effect Storms
Cold Air Moving Over Water Surface Steam Fog Cold air off continent moves over relatively warm water surface Fluxes of heat and moisture from water into air (bulk formulae): F ( ) H = ρc D V T air T water (Heat) F ( (, )) v = ρc D V q air q s pt water (Vapor) F = ρc VV (Momentum) M D Note: C = 1.1 x 10 3 + 4. x 10 5 V D
Lidar Observation of Steam Fog
Lidar Observation of Steam Fog
Lidar Observation of Steam Fog
Lake Effect Storm Types Wind/Shear Parallel Bands Shore Parallel Bands Shore based Midlake Mesoscale Vortex
Lake Superior Lake Effect
Shore Parallel Bands Land breeze mesoscale circulation Deeper than wind parallel bands ( up to 4 km AGL) Very intense precipitation over a small area May be short lived or last several days
Lake Ontario Lake Effects
Lake Erie Shore Parallel Band December 24, 2001 Buffalo
Lake Erie Shore Parallel Band December 24, 2001 Buffalo
Lake Michigan Shore Parallel Band
Lake Michigan Shore Parallel Band
Lake Michigan Shore Parallel Band
Lake Michigan Shore Parallel Band
Lake Michigan Shore Parallel Band
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)
Wind or Shear Parallel Bands Rayleigh Benard Instability Relatively shallow, i.e. depth of Boundary Layer So shallow, often can not form a viable precipitation process Long periods of light snow
Lake Michigan Wind/Shear Parallel Band
10 and 13 January, 1998
UW Volume Imaging Lidar at Lake-ICE
Characteristics of Wind Parallel vs. Shore Parallel Bands
Growth of Planetary Boundary Layer Across Lake
Visible Satellite Loop Cloud rolls over water Spectacular Cloud streets over land Effect of lake shoreline Gravity waves perpendicular to flow 1704 UTC - 1748UTC
Detailed Study of Shore Parallel Bands
Sounding and Hodograph of Winds Incident on Western Shore
Rayleigh Numbers
Origins of Bands
Type B Waves
Wave Duct Leading to Type B Bands
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