Chapter 7.2 part 2
Weather Fronts
THINK ABOUT IT….
Why don’t air masses blend and form a new mass?
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Weather Front Video- (Record 2 facts from the video.)
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2.
WWI and Meteorology
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During World War I, European nations stopped broadcasting weather reports, fearing that they would
be used by advancing enemy troops.
This left nonaligned countries such as Norway to develop their own meteorology program.
They discovered that air masses formed from source regions and that these masses traveled with the
winds.
Influenced by the war, they described air masses using military terms.
They imagined Europe as a battleground where different air masses fought like armies trying to
advance on each other.
The boundary between the air masses, where the “battle” occurs, was calledthe front .
Fronts
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Air masses that form from different areas often do not mix because they have different densities.
Warm air is less dense than cold air. When two air masses meet, warm air generally rises.
The area in which two types of masses meet is called a FRONT.
Four Kinds of Fronts
COLD FRONT
A COLD FRONT forms when...
• cold air moves under warm air
• pushes the less dense warm air up
Weather that cold fronts bring….
• thunderstorms
• heavy rain
• snow
• cooler/drier air mass behind it
WARM FRONT
A WARM FRONT forms when...
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warm air moves over cold denser air
warm air gradually replaces cold
Weather that warm fronts bring…
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drizzly rain
followed by clear and warm weather
OCCLUDED FRONT
An OCCLUDED FRONT forms when...
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a warm air mass is caught
between two colder air masses
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the coldest air mass moves under
and pushes up the warm air mass
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coldest air mass moves forward until
meets a cold air mass that is less dense
then pushes the lesser cold mass up
Weather that occluded fronts bring...
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large amounts of rain/snow
cool temperatures
STATIONARY FRONT
A stationary front forms when...
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Cold air mass meets warm air mass
Neither has enough force to lift the
warm air mass over the cold air mass
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Fronts “stay” separated because
not enough wind to keep air masses pushing
against each other
Stationary fronts bring...
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many days of cloudy & wet weather
Comprehension Check
List and describe the four types of fronts?
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