Download Weather Patterns Air Masses and Fronts

Weather Patterns
Air Masses and Fronts
Section 17.1
Air Masses
Arctic
Continental
polar
Maritime
polar
OK
Maritime
tropical
Continental
tropical
Huge bodies of air that have similar temperature,
humidity, and air pressure
Fronts
• When an air mass moves into an area and
interacts with other masses, it causes the
weather to change.
• The boundary where air masses meet
becomes a front
Cold Front
Fast moving cold
dense air pushes
slow moving
warm air up
Warm air cools
and precipitates
Since cold air masses move fast they can cause abrupt
weather changes (thunder storms)
After a cold front passes, colder, drier air moves in
bringing clear skies
Warm Front
Fast moving
warm air
overtakes
slow moving
cold air
Less dense warm air moves over dense cold air
Can produce rain or snow
Area likely to become warm and humid
Warm Front
Stationary Fronts
Cold air and warm
air meet but
neither can move
the other.
Produces rain, snow
or fog
Can last for several
days
Standoff between two air masses
Stationary Fronts
Standoff between two air masses
Occluded Front
A warm air mass is caught between two cold air masses
The denser air mass pushes the warm air mass up
The two cold air masses may mix underneath the warm one
The warm air mass is cut off (occluded) from the ground
The warm air cools, condenses and may precipitate
Cyclones & Anticyclones
• Fronts become distorted because of things
like mountains or jet streams (bending)
• Bending can cause swirls which can
create low pressure centers
Cyclones
• Swirling low pressure system
• Air pressure decreases as warm air rises
• Cooler air blows inward toward the low
pressure area
• Coriolis effect causes the wind to spin
counterclockwise in northern hemisphere
• Associated with clouds, wind, and
precipitation
Anticyclones
• High pressure systems
• Air swirls outward in clockwise direction in
northern hemisphere
• Cool air moves downward and heats up
lowering relative humidity
• Associated with dry, clear weather