Air Masses and Weather Fronts

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Air MassesandWeather Fronts
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Why do we need to know anything about weather
fronts?
When we look at weather fronts we can see what
type of weather we are having. We can prepare for
severe weather when looking at the types of
weather fronts.
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A boundary between two distinct air masses is
called a weather front .
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Weather Front Symbols
????Which is Which????
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Types of Fronts

• There are 4 types of fronts
• Cold Fronts
• Warm Fronts
• Stationary Fronts
• Occluded Fronts

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Symbol
Warm Fronts
A warm front occurs when a less dense air mass
rides up over a more dense air mass.
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Clouds, Storms, and rain accompany warm
fronts. Moving warm air mass collides with a
slowly moving cold air mass

• Warm Front Animation
• http//ww2010.atmos.uiuc.edu/(Gl)/guides/crclm/act
  /gifs/fpr4.gif
• http//earthsci.org/processes/weather/weaimages/2e
  .gif

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Symbol
Cold Fronts
A cold front occurs when a more dense air mass
pushes under a less dense air mass.
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Cold air is dense and tends to sink, while warm
air is less dense and tends to rise. Rapidly
moving cold air runs into a slowly moving warm
air mass and pushes the lighter warm air upward.

• Cold front animation
• http//ww2010.atmos.uiuc.edu/(Gl)/guides/crclm/act
  /gifs/fpr2.gif
• http//earthsci.org/processes/weather/weaimages/2g
  .gif

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Cold Fronts can cause heavy snow or ice if there
is enough water vapor in the air.
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Symbol
Occluded Front

• A warm air mass is caught between two cooler air
  masses

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Occcluded FrontsThe two cooler air masses meet
in the middle and may mix. The warm air mass is
cut off (or occluded) from the ground.

• http//www.uwsp.edu/geo/faculty/ritter/images/atmo
  sphere/weather/cold_occlusion.gif

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Stationary Front
Symbol

• Warm air mass and cold air mass meet
• Neither has enough force to move the other so
  they just stay in the same place.
• Where they meet, water vapor in the warm air
  condenses into rain, snow, fog or clouds
• Can stall out for days

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Stationary Fronts

• Stationary Front Animation
• http//www.usatoday.com/weather/tg/wsfront/wsfront
  .htm

Unlike a fast-moving front, Stationary fronts
often bring several days of cloudy, wet weather
that can last a week or more.