Air Masses and Fronts
Chapter 16 Section 2
Air Mass - large body of air where temperature and moisture content are
similar throughout.
The moisture content and temperature of an air mass are determined by the
area over which the air mass forms.
Air Masses that affect weather in North America:
Maritime (m) forms over water; wet
Continental (c) forms over land; dry
Polar (P) forms over the polar regions; cold
Tropical (T) develops over the Tropics; warm
Most of the cold winter weather in the United States is influenced by three
polar air masses. A continental polar air mass forms over northern Canada,
which brings extremely cold winter weather to the United States. In the
summer, a cP air mass generally brings cool, dry weather.
A maritime polar air mass that forms over the North Pacific Ocean is cool
and very wet. It brings cool, foggy weather in the summer.
A maritime polar mass that forms over the North Atlantic Ocean brings cool,
cloudy weather and precipitation to New England. In the summer, the air
mass brings cool weather and fog.
Four warm air masses influence the weather in the United States.
Maritime Tropical air masses develop over the Pacific Ocean, Gulf of
Mexico, and the Atlantic Ocean. These air masses bring hot and humid
weather. Thunderstorms and hurricanes develop. In the winter they bring
mild, cloudy weather.
A continental tropical air mass forms over the deserts of northern Mexico
and the southwestern United States. This brings clear, dry, and hot weather.
Fronts – the area in which two air masses meet
Cold front – forms where cold air move under warm air, which is less dense,
and pushes the warm air up. Cold fronts move quickly and bring
thunderstorms, heavy rain, or snow.
Warm front – a warm front forms where warm air moves over cold, denser
air. In a warm front, the warm air gradually replaces the cold air. Warm
fronts bring drizzly rain and are followed by clear and warm weather.
Occluded Front – forms when a warm air mass is caught between two colder
air masses. The coldest air mass moves under and pushes up the warm air
mass. The coldest air mass moves forward until it meets a cold air mass that
is warmer and less dense. The colder of these two air masses moves under
and pushes up the warmer air mass. Sometimes, the two colder air masses
mix. An occluded front has cool temperatures and large amounts of rain and
snow.
Stationary Front – forms when a cold air mass meets a warm air mass. Both
air masses do not have enough force to lift the warm air mass over the cold
air mass. The two air masses remain separated. A stationary front often
brings many days of cloudy, wet weather.
Cyclones – areas that have lower pressure than the surrounding areas and
have winds that spiral toward the center.
Anticyclone – areas that have high pressure.
Low pressure areas – stormy weather
High pressure areas – fair weather
Air Masses and Fronts
Chapter 16 Section 2
______________________ - large body of air where temperature and
moisture content are similar throughout.
The ____________________ content and temperature of an air mass are
determined by the area over which the air mass forms.
Air Masses that affect weather in North America:
1._______________________ (m) forms over water; wet
2.____________________ (c) forms over land; dry
3.____________________ (P) forms over the polar regions; cold
4._____________________ (T) develops over the Tropics; warm
Most of the ____________ winter weather in the United States is influenced
by three polar air masses. A continental polar air mass forms over northern
_______________, which brings extremely cold winter weather to the
United States. In the summer, a cP air mass generally brings
_______________ weather.
A ___________________ polar air mass that forms over the North Pacific
Ocean is cool and very ___________. It brings cool, foggy weather in the
____________________.
A maritime polar mass that forms over the North Atlantic Ocean brings cool,
____________________ weather and precipitation to New England. In the
summer, the air mass brings _____________ weather and fog.
Four warm air masses influence the weather in the United States.
Maritime Tropical air masses develop over the _____________ Ocean, Gulf
of Mexico, and the _________________ Ocean. These air masses bring
___________ and humid weather. Thunderstorms and hurricanes develop.
In the winter they bring _____________, cloudy weather.
A continental tropical air mass forms over the ____________of northern
Mexico and the southwestern United States. This brings clear, dry, and
_________________weather.
Fronts – the area in which two air masses meet
1.___________________ – forms where cold air move under warm air,
which is less dense, and pushes the warm air up. Cold fronts move quickly
and bring __________________________, heavy rain, or snow.
2._______________________ – a warm front forms where warm air moves
over cold, denser air. In a warm front, the warm air gradually replaces the
cold air. Warm fronts bring drizzly _____________ and are followed by
clear and warm weather.
3.______________________ – forms when a warm air mass is caught
between two colder air masses. The coldest air mass moves under and
pushes up the warm air mass. The coldest air mass moves forward until it
meets a cold air mass that is warmer and less dense. The colder of these two
air masses moves under and pushes up the warmer air mass. Sometimes, the
two colder air masses mix. An occluded front has _______________
temperatures and large amounts of _______________ and snow.
4._______________________________ – forms when a cold air mass meets
a warm air mass. Both air masses do not have enough force to lift the warm
air mass over the cold air mass. The two air masses remain separated. A
stationary front often brings many days of cloudy, ___________ weather.
______________________________ – areas that have lower pressure than
the surrounding areas and have winds that spiral toward the center.
___________________________ – areas that have high pressure.
Low pressure areas –_______________weather
High pressure areas – ______________ weather