Transcript Cloud Resolving Model Simulation of the Convective

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