Download Mid Latitude Lows - Smyth County Schools

Mid Latitude Lows
By
Diana L. Duckworth
Rustburg High School
Campbell County, VA
Signature
Cloud Pattern
Comma
Photo: EOS
Low forms as
cold air pushes
south & warm air
pushes north
along polar front.
Sets up
counterclockwise
rotation;
converging air
rises.
http://encyclopedia.jrank.org/Cambridge/entries/images/general%2
0circulation%20models%201.jpg
http://www.ametsoc.org/amsedu/dstreme/
Cold Sector
weather is
warm front
weather:
steady ppt.
L
Cold Sector
Form depends
on thermal
structure of
atmosphere.
Warm Sector
Warm sector
weather is
Thunderstorms
Boundaries between types are mixed!
Warm clouds
DPT > 0°C
Cold clouds
D.P.T. < 0°C
Warm air
Cold air
SNOW
SLEET
FREEZING
RAIN
RAIN
Wintry Mix
Warm front wraps around the Low into the precipitation shield.
SNOW
MIX
RAIN
http://www.ametsoc.org/amsedu/dstreme/
SNOW
RAIN
http://www.ametsoc.org/amsedu/dstreme/
Low goes up coast – nor’easter
SNOW
MIX
http://www.ame
tsoc.org/amsed
u/dstreme/
RAIN
Counterclockwise circulation – coastal winds from the northeast!
http://www.ametsoc.org/amsedu/dstreme/
Winter Storms
• Low passes to west up Ohio Valley
– Showers & possibly thunderstorms depending
on temperatures in warm sector
• Low passes over central Virginia
– Wintry mix, depending on temperatures
• Low passes just to south & up coast near
Hatteras
– SNOW!!!! & LOTS OF IT
Predicting the track of a MidLatitude Low
• Steering Winds
– At 500 mb level
– Low moves in the direction of the steering
winds
– Moves at ½ the speed of steering winds
http://www.ametsoc.org/amsedu/dstreme/
http://www.ametsoc.org/amsedu/dstreme/
http://www.ametsoc.org/amsedu/dstreme/
http://www.ametsoc.org/amsedu/dstreme/
http://www.ametsoc.org/amsedu/dstreme/
http://www.ametsoc.org/amsedu/dstreme/
http://www.ametsoc.org/amsedu/dstreme/
http://rst.gsfc.nasa.gov/Sect14/FIG07_015.jpg
Storm Tracks
• Storm tracks follow polar front & jet
stream.
• Intensify in troughs with jet streak (very
high jet stream winds – 150 mph or more)
• Polar front is in Canada in summer, so
Virginia gets cold front weather.
• Polar front moves south into U.S. in winter,
so Virginia gets warm front weather (more
in precipitation shield).
http://www.ametsoc.org/amsedu/dstreme/
http://www.ametsoc.org/amsedu/dstreme/