Lake-Effect Snow
description
Transcript of Lake-Effect Snow
![Page 1: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/1.jpg)
Lake-Effect Snow• A “Fair weather” event
– Occurs after the passage of a mid-latitude cyclone
– Areas downwind of relatively warm lakes can receive *incredibly heavy snow* while nearby areas have improving weather
![Page 2: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/2.jpg)
Up on the roof!
![Page 3: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/3.jpg)
Where is my car?
![Page 4: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/4.jpg)
Snowed in!
![Page 5: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/5.jpg)
Ten foot Wall of Snow, ‘77
![Page 6: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/6.jpg)
Up on the roof again ‘77
![Page 7: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/7.jpg)
Sea of snow and cars, ‘77
![Page 8: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/8.jpg)
Average Temps: Lake Vs. Air
Unstable season
![Page 9: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/9.jpg)
LAKE EFFECT: Conceptual Model
Green/Red arrows?
![Page 10: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/10.jpg)
LAKE EFFECT: Conceptual Model
Snow intensity: Factors?
How cold is air? (Temp. diff Lake to Air)
How deep is cold air?
How long is air over lake (fetch)?
![Page 11: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/11.jpg)
LAKE EFFECT: Conceptual Model
South-><-North Narrow bands of heavy snow2-20 miles wide, 50-250 miles long
![Page 12: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/12.jpg)
SEASONAL SNOWFALL
![Page 13: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/13.jpg)
PA Average Annual Snowfall
92”
41”19”
47”
120”
5”
10”
50” 65”
0”
Red number is amount that’s lake-effect snow
![Page 14: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/14.jpg)
TERRAIN AND PRECIPITATION
![Page 15: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/15.jpg)
LAKE EFFECT: Conceptual Model
![Page 16: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/16.jpg)
LAKE-EFFECT SNOW “LONG FETCH”
Bands oriented parallel to the mean wind from sfc to 850mb
![Page 17: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/17.jpg)
LAKE-EFFECT SNOW “SHORT FETCH”
Bands oriented parallel to the mean wind from sfc to 850mb
![Page 18: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/18.jpg)
LAKE-EFFECT SNOW: WESTERLY WIND
COLD AIR
Bands oriented parallel to the mean wind from sfc to 850mb
MULTIPLE BANDS SINGLE BAND
Short fetch Long fetch
![Page 19: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/19.jpg)
LAKE-EFFECT SNOW: NORTHWEST WIND
COLD AIR
Bands oriented parallel to the mean wind from sfc to 850mb
![Page 20: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/20.jpg)
![Page 21: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/21.jpg)
Great Lake Snow Bands
![Page 22: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/22.jpg)
Great Lake Snow Bands?
![Page 23: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/23.jpg)
Great Lake Snow Bands?
![Page 24: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/24.jpg)
Great Lake Snow Bands?
![Page 25: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/25.jpg)
Great Lake Snow Bands
![Page 26: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/26.jpg)
LAKE-EFFECT SNOW BAND
![Page 27: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/27.jpg)
CURTAIN OF DEATH!!!
![Page 28: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/28.jpg)
LAKE-EFFECT SNOW
![Page 29: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/29.jpg)
Lake-Effect Snow• Location wind direction/speed• Intensity
– Stability• Tlake-T850mb>13C, less if synoptic support• Larger the difference, generally heavier the snow• Depth of cold air … consult mr. sounding!
Deeper cold air Deeper cloud Heavier snow!– Fetch
• Longer distance/time more modification heavier snow• Need ~40 mi. of fetch, over 120mi.can bring intense snows• Single bands vs. multiple bands
– Wind Shear• Little or no directional shear heavier snow
– Topography• Upslope regions favored for heavier snow
– Best events have synoptic-scale support• Approaching 500mb shortwave
– “lifts inversion” ->> deeper convection• 700mb RH >70% …. Good indicator of synoptic support• Right conditions can bring >3”/hour rates !!!
– Distance inland: multiply 850mb wind speed by ~1.5
![Page 30: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/30.jpg)
Where else does LE occur?
![Page 31: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/31.jpg)
CLASSIC “BIG” LAKE EFFECT: Surface pattern
* TLAKE-T850mb>=13C-”general” rule
Canadian High- cp, Arctic air
Cold Advection
* Occurs if -8 to -12 C diff. in certain situations
![Page 32: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/32.jpg)
CLASSIC “BIG” LAKE EFFECT: Surface pattern
![Page 33: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/33.jpg)
CLASSIC “BIG” LAKE EFFECT: 500mb pattern
500mb Pattern
![Page 34: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/34.jpg)
LAKE EFFECT with Synoptic Support
High RH is a good indicator of “Synoptic” support
![Page 35: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/35.jpg)
Buffalo Snow: Christmas 2001
![Page 36: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/36.jpg)
Buffalo Snow: Christmas 2001
![Page 37: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/37.jpg)
Buffalo Snow: Christmas 2001
![Page 38: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/38.jpg)
Lake-Effect?
![Page 39: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/39.jpg)
Lake-effect?
![Page 40: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/40.jpg)
WINTER WX: LAKE EFFECT• IMPORTANT ELEMENTS:
– Caused by cold air over warm lake (* Tlake-T850mb>13C)• * less if synoptic support
– 850mb T’s < -7C, If warmer -> rain– Bands // to mean wind from sfc to 850mb– Longer fetch -> more intense the snow
• Need ~40 mi. of fetch, over 120mi.can bring intense snows– Single bands: more intense, wind // to long axis of lake– Multiple bands: less intense, wind // to shorter axis of lake– Low vertical wind shear is favorable– Best events have synoptic-scale support
• Approaching 500mb shortwave– “lifts inversion” ->> deeper convection
• 700mb RH >70% …. Good indicator of synoptic support• Right conditions can bring >3”/hour rates !!!
– Distance inland: multiply 850mb wind speed by ~1.5
![Page 41: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/41.jpg)
Lake effect: NGM model
![Page 42: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/42.jpg)
Lake effect: ETA coarse model
![Page 43: Lake-Effect Snow](https://reader035.fdocuments.net/reader035/viewer/2022081506/56815147550346895dbf68b7/html5/thumbnails/43.jpg)
Lake effect: ETA fine res