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Lake Effect Storms

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):. Lidar Observation of Steam Fog. Lidar Observation of Steam Fog. Lidar Observation of Steam Fog.

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Lake Effect Storms

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  1. Lake Effect Storms

  2. 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):

  3. Lidar Observation of Steam Fog

  4. Lidar Observation of Steam Fog

  5. Lidar Observation of Steam Fog

  6. Lake Effect Storm Types • Wind/Shear Parallel Bands • Shore Parallel Bands • Shore based • Midlake • Mesoscale Vortex

  7. Lake Superior Lake Effect

  8. 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

  9. Lake Ontario Lake Effects

  10. Lake Erie Shore Parallel BandDecember 24, 2001 Buffalo

  11. Lake Erie Shore Parallel BandDecember 24, 2001 Buffalo

  12. Lake Michigan Shore Parallel Band

  13. Lake Michigan Shore Parallel Band

  14. Lake Michigan Shore Parallel Band

  15. Lake Michigan Shore Parallel Band

  16. Lake Michigan Shore Parallel Band

  17. 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

  18. 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)

  19. 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

  20. Lake Michigan Wind/Shear Parallel Band

  21. 10 and 13 January, 1998

  22. UW Volume Imaging Lidarat Lake-ICE

  23. Characteristics of Wind Parallel vs. Shore Parallel Bands

  24. Growth of Planetary Boundary LayerAcross Lake

  25. Visible Satellite Loop • Cloud rolls over water • Spectacular Cloud streets over land • Effect of lake shoreline • Gravity waves perpendicular to flow 1704 UTC - 1748UTC

  26. Detailed Study of Shore Parallel Bands

  27. Sounding and Hodograph of Winds Incident on Western Shore

  28. Rayleigh Numbers

  29. Origins of Bands

  30. Type “B” Waves

  31. Wave Duct Leading to Type”B” Bands

  32. 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)

  33. 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

  34. 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

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