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
5
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
21
Front’s Bell work
1.
2.
3.
4.
5.
Moves in the fastest _________
Steady, light precipitation ___________
Precedes cool, clear weather _________
Has a slope of 1:200 km __________
Does not advance forward or back for
days ________
6. Produces stratus clouds _________