Highs,%20Lows,%20and%20Fronts

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Highs, Lows, and Fronts
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Highs, Lows, and Fronts
Name Clouds before Front Arrives Air that Rises Weather after Front Passes Time Required to Pass
Warm Front Cirrus, Altostratus Warmer Warm, Humid, Cloudy Long
Cold Front Cumulonimbus Warmer Dry, Cold, Clear Short
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Description of a Cold Front

• What does the H on a weather map represent?
• It refers to a region of High Pressure.

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Description of a Cold Front

• What sort of weather will you find there?
• Clear, sunny, cool, stable, mild winds.

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Description of a Cold Front

• One morning you wake up and the sky is clear. By
  noon, clouds that started like jet trails are
  making streaks across the sky.
• By dinner time, the clouds have thickened into a
  lower, grey, featureless blanket over the sky.
• What is happening in terms of fronts?
• What do you think the weather will be like that
  night and the following day?

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Description of a Cold Front

• A warm front is coming in, hence the formation of
  cirrus clouds.
• The thick, grey blanket are altostratus clouds.

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Description of a Cold Front

• By night time, it is likely that nimbostratus
  clouds will have formed and light rain will begin
  to occur.
• The light rain will continue into the next day
  because warm fronts pass slowly.

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Highs and Lows

• Air moves from an area of high pressure to an
  area of low pressure.
• As cool air descends, it becomes more dense and
  draws the air from above.
• This describes a high pressure system.

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Highs and Lows

• At the base of a high pressure system, air is
  pushed out. Why?
• To equalize pressure, air has to move from high
  pressure to low pressure.

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Highs and Lows

• Because of the Coriolis Effect, the air at the
  base of a high pressure system veers to the right
  in the Northern Hemisphere.
• As a result, high pressure systems move in a
  clockwise direction, called an anticyclone.

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Quick Questions

• Why do high pressure systems cause clear skies?
• Cool air descending prevents cloud formation b/c
  it is not a moist/humid as warm, cloud forming
  air.
• Cool air cant hold very much moisture.

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Quick Questions

• Why do high pressure systems cause weather to
  stay the same for days?
• B/c they are large, usually the size of an entire
  air mass, therefore they take a while to move out
  of an area.

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Cold Fronts Warm Fronts
C O M P A R E Both are boundary lines between 2 different air masses. Both are formed when a warmer and a cooler air mass meet each other. Both leave the temperature of the air different then before they arrived. Both involve cloud formation and rain/snow. Both create rising air. Both are boundary lines between 2 different air masses. Both are formed when a warmer and a cooler air mass meet each other. Both leave the temperature of the air different then before they arrived. Both involve cloud formation and rain/snow. Both create rising air.
C O N T R A S T Created when a cooler air mass overtakes a warmer air mass. Warm air rises b/c it is pushed up by the cool air and b/c it is less dense. Steeply sloping curved line front. Heavy rain and wind. Passes through quickly. Cool, dry, and clear skies after Mainly cumulus type clouds Created when warmer air mass overtakes a cooler air mass. Warm air rises just b/c it is less dense. Gentle sloping straight lined front. Light rain and wind. Passes through slowly. Warm, humid, and cloudy after. Mainly stratus type clouds.