Air Masses and Fronts
Warm Up: What type of rock is
formed from cooling lava?
 Air Mass VIDEO Clip 
Air Masses
• Air masses have the same properties as the surface
over which it develops:
Maritime = Wet
Continental = Dry
Polar = Cold
Tropical = Warm
mP = wet/cold
cP = dry/cold
mT = wet/warm
cT = dry/warm
Air Masses in North America
Fronts
•
A front is the boundary where two air
masses meet.
WARM AIR
•
Types of fronts:
1.
2.
3.
4.
Warm Front
Cold Front
Occluded Front
Stationary Front
FRONT
COLD AIR
Front VIDEO Clip 
Cold Front
• Cold dense air
pushes under a warm
air mass.
• The cold dense air
moves faster and
causes the warm air
rises quickly.
• Narrow bands of
violent storms form.
Why do cold fronts bring heavy rain
and storms?
• Cold air interacting with warm air = a sudden drop in
temperature = CONDENSATION occurs quickly and a
fast difference in pressure
• Creates cumulonimbus clouds
• Cold dense fast moving air = high winds
What you see in a weather map!
Cold Front Video Clip
Warm Front
• Warm air slides over
departing cold air.
• Large bands of
precipitation form
Why do warm fronts bring mild
weather?
• It’s more difficult for the warm air to move
against the cold dense air so there is a gradual
difference in pressure and temperature
What you see in a weather map!
Warm Front Video Clip
Occluded Front
• Two cold air masses merge and force
warm air between them to rise quickly.
• Strong winds and heavy precipitation will
occur.
Why do occluded fronts bring
heavy rain and storms?
• Cold air that is more dense moves into an area
of low pressure = CONDENSATION occurs
quickly
• Forms cumulonimbus and nimbostratus clouds
What you see in a weather map!
Stationary Front
• Warm and/or cold front
stops moving.
• Light wind and
precipitation may occur
across the front
boundary.
Why do stationary fronts bring long
light precipitation?
• Neither front is strong enough to move the other
• Can stay put for days
• Differences in temperature = rain or snow
What you see in a weather map!
Cyclones and Anticyclones
• Areas of HIGH and LOW pressure
• Cyclone = LOW PRESSURE = spin
counterclockwise = associated with storms and
precipitation
• Anticyclone = HIGH PRESSURE = spin clockwise
= associated with fair weather.
Cyclones and Anticyclones in the
USA
Cyclone Video Clip 