Air Masses and Fronts

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Air Masses and Fronts
Warm Up What type of rock is formed from
cooling lava?
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? Air Mass VIDEO Clip ?
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Air Masses

• Air masses have the same properties as the
  surface over which it develops
• Maritime Wet
• Continental Dry
• Polar Cold
• Tropical Warm

mP wet/cold cP dry/cold mT wet/warm cT
dry/warm
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Air Masses in North America
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Fronts

• A front is the boundary where two air masses
  meet.
• Types of fronts
• Warm Front
• Cold Front
• Occluded Front
• Stationary Front

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Front VIDEO Clip ?
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Cold Front

• Cold dense air pushes under a warm air mass.
• The cold dense air moves faster and causes the
  warm air rises quickly.
• Narrow bands of violent storms form.

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Why do cold fronts bring heavy rain and storms?

• Cold air interacting with warm air a sudden
  drop in temperature CONDENSATION occurs quickly
  and a fast difference in pressure
• Creates cumulonimbus clouds
• Cold dense fast moving air high winds

What you see in a weather map!
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Cold Front Video Clip
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Warm Front

• Warm air slides over departing cold air.
• Large bands of precipitation form

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Why do warm fronts bring mild weather?

• Its more difficult for the warm air to move
  against the cold dense air so there is a gradual
  difference in pressure and temperature

What you see in a weather map!
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Warm Front Video Clip
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Occluded Front

• Two cold air masses merge and force warm air
  between them to rise quickly.
• Strong winds and heavy precipitation will occur.

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Why do occluded fronts bring heavy rain and
storms?

• Cold air that is more dense moves into an area of
  low pressure CONDENSATION occurs quickly
• Forms cumulonimbus and nimbostratus clouds

What you see in a weather map!
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Stationary Front

• Warm and/or cold front stops moving.
• Light wind and precipitation may occur across the
  front boundary.

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Why do stationary fronts bring long light
precipitation?

• Neither front is strong enough to move the other
• Can stay put for days
• Differences in temperature rain or snow

What you see in a weather map!
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Cyclones and Anticyclones

• Areas of HIGH and LOW pressure
• Cyclone LOW PRESSURE spin counterclockwise
  associated with storms and precipitation
• Anticyclone HIGH PRESSURE spin clockwise
  associated with fair weather.

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Cyclones and Anticyclones in the USA
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Cyclone Video Clip ?