Winter Storms and Northeasters

1
Winter Storms and Northeasters
Robert E. Davis
Dept. of Environmental Sciences
University of Virginia
Email red3u_at_virginia.edu
Virginia Mitigation Summit June 17, 2004
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Noreasters and Snowfall in Virginia
Noreasters
Snow
Noreaster- generated snowfall
Many Virginia snow events are not linked to
noreasters
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WINTER STORM INGREDIENTS
Cold Air Damning
1. Sufficient cold air source
4
WINTER STORM INGREDIENTS
Moist Air
2. Sufficient moisture
Moist Air
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WINTER STORM INGREDIENTS
winds
L
3. Lifting mechanism (the storm)
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WINTER STORM INGREDIENTS
H
L
Moist Air
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TIMING IS EVERYTHING
H
Arrival of storm does not coincide with cold
air Warm air from Atlantic decreases vertical
thickness of cold air mass
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TIMING IS EVERYTHING
L
L
Forward speed too fast Low snow accumulations
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WINTER STORM INGREDIENTS
L
L
L
Track too far inland Not enough moisture
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THE SNOWMAKER TRACK
Ideal track for producing snow in the
Mid-Atlantic
Heaviest snow frequency



Storm Track
(Knappenberger and Michaels, 1993)
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NOREASTERS
A cyclonic storm of the east coast of North
America, so called because the winds over the
coastal area are from the northeast (Glossary
of Meteorology)
L
New England gale force winds winter high
waves beach erosion
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FACTORS THAT DETERMINE WAVE HEIGHTS IN DEEP WATER
wind speed wind duration fetch
Wave height climatologies can be hindcasted
from historical weather records
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IMPORTANCE OF STORM TRACK
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NOREASTER FORMATION REGIONS
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Noreaster Type by Class
I
IV
Most Class IV and V storms form near the Bahamas
or Florida
II
V
III
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NOREASTERS AND VIRGINIA SNOW
Most major snowstorms in Virginia are caused
by large noreasters
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NOREASTER SEASONALITY
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JET STREAM
1) Boundary between warm, tropical and cold,
polar air masses 2) Size and strength vary
seasonally 3) Linked to mid-latitude storms at
surface 4) Linked to storm tracks
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JANUARY
JULY
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Mid-latitude storms derive their energy from the
jet stream
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MID-LATITUDE STORM FORMATION REGIONS
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JANUARY MIDLATITUDE STORM TRACKS
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JULY MIDLATITUDE STORM TRACKS
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PREFERRED WINTER STORM TRACKS
L
L
L
L
L
L
Continental Track
L
L
Coastal Track
L
L
(After Hayden, 1981)
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Golfers track
Snowmaker track
(Knappenberger and Michaels, 1993)
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H
ASH WEDNESDAY STORM March, 1962

• Strong high to north
• Storm track off coast
• (Bahamas Low)
• Slow-moving
• Strong northeast winds to the
• north of storm
• Long fetch, strong winds from same
• direction for long duration

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ASH WEDNESDAY STORM, MARCH, 1962 Snowfall (inches)
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STORM OF THE CENTURY March, 13 1993 7 a.m. EST
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Storm of the Century Surface
weather map 3/13/1993 7 p.m., EST
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Mean Annual Snowfall
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Record-Holding Snowfall Seasons
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EL NINO AND NOREASTERS (ALL STORMS)
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EL NINO AND NOREASTERS (STRONG STORMS)
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EL NINO AND VIRGINIA PRECIPITATION
LA NINA
EL NINO
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EL NINO AND VIRGINIA TEMPERATURE
LA NINA
EL NINO
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EL NINO AND VIRGINIA SNOWFALL
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El Nino
La Nina
30
25
20
VIRGINIA SNOWFALL (INCHES)
15
10
5
0
-8
-6
-4
-2
0
2
4
JAN-MAR EL NINO STATUS
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Winter Storms and Northeasters
Robert E. Davis
Dept. of Environmental Sciences
University of Virginia
Email red3u_at_virginia.edu
Virginia Mitigation Summit June 17, 2004
Thanks to Chip Knappenberger Jerry Stenger Pat
Michaels