What is an AIR MASS?

An air mass is a huge body of air that has similar characteristics

as the area they were formed.

Air Masses are named based on where they FORMED…

= TROPICAL

= POLAR

= MARITIME (means sea… wet)= CONTINENTAL (means land… dry)

Air Masses classified by…

MOISTURETEMPERATURE

COLDHOT

WETDRY

How do these air masses move?

JET STREAM JET STREAM

Prevailin

g

Westerlie

sPre

vailing

Westerlie

s

That’s why weather generally moves WEST to EAST

in the U.S.

Air masses are steered by the jet stream.

What happens when air masses meet?

• Air masses don’t mix easily.• The line between air masses is called

a front.

Warm FrontA warm air mass overtakes a slow-moving cold air mass.

Cold Fronts and Warm Fronts

Cold FrontA fast-moving cold air mass overtakes a warm air mass.

Cold Fronts and Warm Fronts

A warm air mass is caught between 2 cooler air masses. Warm air mass is pushed up.

Occluded Front

Cold and warm air meet, but neither can move the other. Creates “standoff”

Stationary Front

Front How it Forms Type of Weather

A fast-moving cold air mass overtakes a warm air mass.

Clouds form. If warm air is humid, rain/snow may fall.Possible thunderstorms.

A warm air mass overtakes a slow-moving cold air mass.

Scattered clouds. Light rain or snow.May last several days.

Cold and warm air meet, but neither can move the other. Creates “standoff”

Rain, snow, clouds, or fog that may last for days.

A warm air mass is caught between 2 cooler air masses. Warm air mass is pushed up.

Temperature gets cooler. Clouds and rain may form.

Compare/Contrast Chart - Types of FrontsC

old

War

m

Occ

lude

d St

atio

nary