Weather Fronts

cP air mass moves south

The front of the cP air mass is obvious by the drastic difference in temperatures behind and in front of the air mass

A drastic difference in temperatures indicates a front

Locate the cold and warm front

4 Types of Fronts

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Fronts• Boundary surfaces that separate air masses of

different DENSITIES.• one air mass is usually WARM and MOIST, the

other one COLD and DRY• vary in size: 15-200 km wide• defined by their temperatures• air masses move at different speeds and “clash”• the warmer, less dense air always forced aloft (up)• warm air overlies cold air and a slope is produced.• form mid-latitude cyclones• produce precipitation and severe weather.

Fronts

Warm Front• Symbol• Speed• Slope• Clouds• Precipitation• Weather• Winds

Cold Front

Warm Fronts• Warm air moves to occupy an area formerly

covered by cooler air.

• Warm air masses: mT • from Gulf of Mexico, or California,

Mexico coast

Warm fronts

• Very gradual slope: 1:200km• Speed: advance slowly 15 mph – 20 mph• Clouds: cirrostratus, altostratus, nimbostratus• Precipitation: light to moderate, over a wide

area, long period of time.• Weather: temps. gradually rise, fog, freezing rain• Barometer: dropping below 30 in.• Winds: from east to SW

Warm Front

Unstable air mass

Warm Front Precipitation

Cold Front

• cP continental polar air (Canada) actively advances into an area formerly occupied by warm air.

Cold Fronts

• Slope: Twice as steep: 1:100 km• Advance FAST: 20 mph-50 mph• Clouds: altocumulus, then towering cumulonimbus• Precipitation: heavy downpours, wind gusts over

short duration• Weather: violent weather, temperature drops, clear,

fair weather after• Barometer: rising (above 30 in.)• Winds: shift from SW to NW

Cold Front

Thunderstorm Development along a Cold Front

Stationary Fronts

• Air flow is neither toward a cold air mass or a warm air mass

• Air flow is parallel to the front line• The front does not move, or very slowly (after

remaining over an area for several days)• Precipitation is moderate, flooding possible.

Occluded Fronts

Cold-Type• Rapidly moving cold front, overtakes a warm front

• Cold air WEDGES the warm air upward

Warm-Type• Warmer air behind a cold

front “catches-up”• Ex; north Pacific Coast –

warm mP invades the frigid cP air

Occluded Fronts

• Slope: Twice as steep: 1:100 km• Advance fast: 20 mph-50 mph• Clouds: altocumulus, then towering cumulonimbus• Precipitation: heavy downpours, wind gusts over

short duration• Weather: violent weather, temperature drops, clear,

fair weather after• Barometer: rising• Winds: shift from SW to NW

Occluded Front

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Front’s Bell work

1. Moves in the fastest _________

2. Steady, light precipitation ___________

3. Precedes cool, clear weather _________

4. Has a slope of 1:200 km __________

5. Does not advance forward or back for days ________

6. Produces stratus clouds _________