Download 1. Air mass and Fronts

 What is an Air
Mass?
 A large body of air that
has similar
temperature and
moisture throughout
 Usually cover
thousands of square
kilometers
 They are classified by
where they form
 What are the 4
types of air mass?
 Maritime: forms over
water; wet
 Polar: forms over the
polar regions; cold
 Continental: forms
over land; dry
 Tropical: develops over
the tropics; warm
 What are the air
masses that affect
the weather in the
U.S.?
 Maritime Tropical:
forms over the ocean
near the equator; holds
warm, moist air. In the
summer, it brings hot,
humid weather but in
the winter, if it comes
in contact with a cold
air mass, rain and snow
will fall
 Maritime Polar: forms
over the Pacific Ocean in
both winter and summer.
It forms over the cold
North Atlantic Ocean in
the summer. In the
summer, it brings cooler
temperatures to the
eastern U.S. and fog to the
western states. Heavy
snow and cold
temperatures are
produced in the winter.
 Continental Tropical:
forms over land in
Mexico during the
summer. It brings dry,
hot air to the SW
states. It also forms
over land in northern
Canada. In winter, this
cold, dry air mass
causes extremely cold
temperatures in the
U.S.
 Continental Polar:
develops over land in
northern Canada. In
the winter, this air
brings extremely cold
weather to the U.S. In
the summer, it
generally brings cool,
dry weather.
 What is a front?
 When two air masses
that do NOT have the
same properties meet
and they do not mix.
Instead, a boundary
forms that is called a
front.
 The weather at a front
is usually stormy and
unsettled
 Named after whichever
air mass is the
“attacker”.
 What are the 4
types of fronts?
 Cold Front: forms
when a cold air mass
meets and pushes
under a warm air mass.
The cold air mass
forces its way
underneath the warm
air mass and pushes it
upward. Violent
weather is associated
with a cold front and
then fair, cool weather
follows. Travels faster
than warm fronts.
 Warm Front: forms
when a mass of warm
air overtakes a cold air
mass and moves over it.
Light rain and showers
usually accompany it
and then hot, humid
weather follows.
 Occluded Front: when a
cold front overtakes a
warm front. As the warm
air is pushed upward, the
cold air meets cool air. It
may also form when cool
air overtakes a cold front
and warm air is pushed
upward. Produces less
extreme weather than a
cold front or a warm front.
Usually cool temperatures
and large amounts of
precipitation.
 Stationary Front:
formed when a warm
air mass meets a cold
air mass and no
movement occurs.
Rain may fall in an area
for many days. Weather
produced is similar to a
warm front.
Review Video
Vocabulary
 Air Mass –
 Cold Front  Warm Front –
 Stationary Front –
 Occluded Front –
 Jet Stream -