Lake Effect Storms

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Lake Effect Storms
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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)

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(No Transcript)
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Lidar Observation of Steam Fog
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Lidar Observation of Steam Fog
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Lidar Observation of Steam Fog
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Lake Effect Storm Types

• Wind/Shear Parallel Bands
• Shore Parallel Bands
• Shore based
• Midlake
• Mesoscale Vortex

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Lake Superior Lake Effect
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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

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Lake Ontario Lake Effects
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Lake Erie Shore Parallel BandDecember 24, 2001
Buffalo
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Lake Erie Shore Parallel BandDecember 24, 2001
Buffalo
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Lake Michigan Shore Parallel Band
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Lake Michigan Shore Parallel Band
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Lake Michigan Shore Parallel Band
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Lake Michigan Shore Parallel Band
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Lake Michigan Shore Parallel Band
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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

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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)

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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

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Lake Michigan Wind/Shear Parallel Band
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10 and 13 January, 1998
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UW Volume Imaging Lidarat Lake-ICE
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Characteristics of Wind Parallel vs. Shore
Parallel Bands
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Growth of Planetary Boundary LayerAcross Lake
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Visible Satellite Loop

• Cloud rolls over water
• Spectacular Cloud streets over land
• Effect of lake shoreline
• Gravity waves perpendicular to flow

1704 UTC - 1748UTC
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Detailed Study of Shore Parallel Bands
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Sounding and Hodograph of Winds Incident on
Western Shore
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Rayleigh Numbers
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(No Transcript)
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Origins of Bands
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Type B Waves
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Wave Duct Leading to TypeB Bands
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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)

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Predicting Wind Parallel Lake Effect Storms

• Lake temperature minus 850 mb temperature gt13C
• Wind fetch gt100 km
• Wind speed moderate to high, i.e. gt10 m/s

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Predicting Shore Parallel Lake Effect Storms

• Wind nearly parallel to long axis of lake
• Lake temperature minus 850 mb temperature gt13C
  (can occur with less temperature contrast)
• Wind speed light to high, i.e. gt 5 m/s