Lecture 5 lake effect storms
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Lecture 5 Lake Effect Storms. 13.1. Snow climatology highly influenced by lake effects. Why Lake Effect?. In Fall season, lakes are warm, advancing polar air comes across with cold air and strong winds

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Lecture 5 Lake Effect Storms

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Lecture 5 lake effect storms

Lecture 5Lake Effect Storms


Lecture 5 lake effect storms

13.1

Snow climatology highly influenced by lake effects


Why lake effect

Why Lake Effect?

  • In Fall season, lakes are warm, advancing polar air comes across with cold air and strong winds

    • Thermal contrast, together with strong winds across water whips up strong surface fluxes of heat and moisture

    • Near surface warming gives rise to static instability, i.e. near surface warm, moist air underlies cold advancing air above

    • Strong unstable overturning results, producing progressively deeper clouds as air traverses lake

    • If clouds and their precipitation process is sufficiently mature as air approaches lee shore, precipitation reaches surface on lee shore

    • When advancing polar air is sufficiently cold, precipitation will be snow


Cold air moving over water surface steam fog

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):


Lake effect storm types

Lake Effect Storm Types

  • Wind/Shear Parallel Bands

  • Shore Parallel Bands

    • Shore based

    • Midlake

  • Mesoscale Vortex


Lidar observation of steam fog

Lidar Observation of Steam Fog


Lidar observation of steam fog1

Lidar Observation of Steam Fog


Lidar observation of steam fog2

Lidar Observation of Steam Fog


Growth of planetary boundary layer across lake

Growth of Planetary Boundary LayerAcross Lake


Lecture 5 lake effect storms

13.3

Lake effect clouds become deeper and feature and increasingly mature precipitation process as flow traverses lake


Lecture 5 lake effect storms

13B


Visible satellite loop

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

Detailed Study of Shore Parallel Bands


Sounding and hodograph of winds incident on western shore

Sounding and Hodograph of Winds Incident on Western Shore


Rayleigh numbers

Rayleigh Numbers


Origins of bands

Origins of Bands


Type b waves

Type “B” Waves


Wave duct leading to type b bands

Wave Duct Leading to Type”B” Bands


13 6a

Ice Cover Analysis

13.6a


Lecture 5 lake effect storms

13.6b

Water Temperature


Lecture 5 lake effect storms

Lake effect greater in early winter when lakes are relatively warm and ice free

13.7


Lecture 5 lake effect storms

Longer wind Fetch will produce more mature clouds and precipitation process and so more snow. Therefore more snow downwind of where lake is wider

13.9


Predicting wind parallel lake effect storms

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


Lake superior lake effect

Lake Superior Lake Effect


Shore parallel bands

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 Ontario Lake Effects


Lake erie shore parallel band december 24 2001 buffalo

Lake Erie Shore Parallel BandDecember 24, 2001 Buffalo


Lecture 5 lake effect storms

13A


Lake erie shore parallel band december 24 2001 buffalo1

Lake Erie Shore Parallel BandDecember 24, 2001 Buffalo


Lake michigan shore parallel band

Lake Michigan Shore Parallel Band


Lake michigan shore parallel band1

Lake Michigan Shore Parallel Band


Lake michigan shore parallel band2

Lake Michigan Shore Parallel Band


Lake michigan shore parallel band3

Lake Michigan Shore Parallel Band


Lake michigan shore parallel band4

Lake Michigan Shore Parallel Band


Shore parallel bands1

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 bands2

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 shore parallel lake effect storms

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


13 14

13.14


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