Download WX_WEO_110_PPT_13

Ch 8
Air masses, Fronts, & Cyclones
Sec A
• Extratropical Cyclone
– Cyclone not in the tropics
– Also known as
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Frontal Lows
Frontal Cyclones
Wave Cyclones
Frontal Waves
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Air Masses: Named by where they come from:
• From over land or over water
– c for Continental: From Over Land: Dry
– M for Marine: From over the ocean: Moist
• From a geographic region of the Earth:
– Arctic: very cold
– Polar: cold
– Tropical: Warm
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• These air masses are abbreviated:
A, P, T, m, c, mP, mT, cT, cP, etc
• mP is cold and moist
• mT is warm and moist
• cP is cold and Dry
• A is very cold and dry.
• cT can be hot and dry: Toast w/o a Toaster
or warm and moist
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• These
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Front: Represents the movement of an
Air Mass of uniform characteristics
– Warm Front: Leading Edge of a Warm air mass
– Cold Front: Leading Edge of a Cold air mass
– Stationary Front: Cold air mass touching a warm
air mass with little movement
– Occluded front: Cold front overtaking a warm front
overtaking a cool air mass.
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Front
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Frontal Slopes:
– Cold Air masses move under Warm air masses
pushing them up. The moisture in the Warm air
mass condenses and produces precipitation.
– This upward push can span 100 miles on the
ground and up to a mile or more vertically.
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Frontal Slopes:
– Cold Air masses move under Warm air masses
pushing them up. The moisture in the Warm air
mass condenses and produces precipitation.
– This upward push can span 100 miles on the
ground and up to a mile or more vertically.
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Frontal Zones:
– Are not sharp lines but extend for tens or hundreds
of miles
– A cold front pushes the Warm air up faster than
a warm front rises over a cold air mass
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Frontal
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Frontal
Which is more abrupt?
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Frontal
Cold Front: Heavy Precipitation: Storms
Warm Front: Mild Precipitation
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Extratropical Cyclone
Structure and Development
– Depends on Climate
• The mT flow from the Gulf of Mexico
– Geographic features
• The Vertical flows produced by Mountain Chains: The Rockies
– Surface Conditions
• Warm Moist Surface Conditions
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Extratropical Cyclone
Structure and Development
– 1. As a front approaches: Pressure falls
• As it passes the pressure rises: cold fronts
– 2. The sharp change in pressure gradient
across a front, corresponds to a sharp
wind shift and possible
cyclonic wind shear
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Extratropical Cyclone
Structure and Development
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Extratropical Cyclone
Structure and Development
• A frontal low has a high probability of
developing when an upper level short
wave trough moves to within 300 mi. of a
surface stationary front.
• The east side of an upper level short wave
trough is the bad weather side.
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Extratropical Cyclone
Structure and Development
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Extratropical Cyclone
Structure and Development
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Extratropical Cyclone
Structure and Development
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Ch 8
Sec A
Air masses, Fronts, & Cyclones
• Weather Guidelines
– Approaching Warm Front: light steady
precipitation with stratiform clouds
– These warm fronts can produce fog.
– When the air behind a cold front is moist and
unstable, it is characterized by CU clouds
– A high pressure ridge or area is characterized
by downward air movement and SKC
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Weather
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Weather
A Jet Stream Loop
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Weather
A Jet Stream Loop
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Ch 8
Sec A
Airmasses, Fronts, & Cyclones
• Weather
A Jet Stream Loop
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Ch 8
Sec B
Air masses, Fronts, & Cyclones
• Tropical Cyclones and Hurricanes:
a mesoscale cyclonic circulation that
develops in the tropical easterlies.
• They are classified by their intensities
with 1 being the least intense and
5 being the most intense
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Ch 8
Sec B
Airmasses, Fronts, & Cyclones
• Tropical Cyclones and Hurricanes:
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Ch 8
Sec B
Airmasses, Fronts, & Cyclones
• Tropical Cyclones and Hurricanes:
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Ch 8
Sec B
Air masses, Fronts, & Cyclones
• Tropical Cyclones and Hurricanes:
Structure
– Rain Bands: Spiral Arms
– Eye: High Pressure and clear of clouds
– Eye Wall: Strongest Winds
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Ch 8
Sec B
Airmasses, Fronts, & Cyclones
• Tropical Cyclones
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Ch 8
Sec B
Airmasses, Fronts, & Cyclones
• Tropical Cyclones
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