Air Masses and Fronts

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Chapter 29

• Air Masses and Fronts

BFRB Pages 123- 125
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Air Masses

• Large areas (blobs) of the troposphere that have
  approximately the same weather, temperatures and
  humidity
• Air Mass Types - Named for where they develop
  over and come FROM
• Weather changes occur with changes in air masses

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TYPES of Air Masses

• maritime Tropical (mT)- warm humid air
• continental Tropical (cT)- hot (warm) dry air
• maritime Polar (mP)- cold humid air
• continental Polar (cP)- cold dry air
• continental Arctic (cA)- very cold dry air
• THESE ARE ALL LISTED IN THE ESRTs ON PAGE 13 ON
  THE BOTTOM!
• There are no mA air masses WHY???

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Fronts

• boundary between two air masses
• bring changes in the weather (from west to east)
• VIF!!!! - Fronts are named for the air that is
  behind them
• The 4 types of fronts and their symbols are
  listed in the ESRTs on Page 13 on the bottom

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WARM AIR MASS
COLD AIR MASS
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Air Mass Army Analogy

• Think of air masses as an army front (the army is
  BEHIND the frontline)
• At the Front there is FIGHTING and lots of
  VIOLENCE (stormy weather)
• Behind the front (inside the air mass) the
  general sits on his duff and watches the
  goings-on while enjoying the nice weather!

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NICE WEATHER
FIGHTING - STORMS
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Cold Front

• Cold dense air pushes warm less dense air up and
  out of the way
• Cold fronts usually move very quickly and bring
  short periods of showers/thunderstorms
• Lower temperatures are behind the front
• SYMBOL the direction of the arrows points
  towards the direction the front is MOVING

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Cross Sectional View
Overhead View on Map
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Cross Section View Why does the cold air mass
stay near the ground and lift the warm air mass
up?
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Warm Front

• Warm air moves up and over the cold front as it
  slowly displaces the cold air
• Warm fronts move slowly, and bring many days of
  steady precipitation
• Higher temperatures are behind the front
• SYMBOL direction of semi-circles is the
  direction the front is moving

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Cross Sectional View
Overhead View on Map
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Cross Section View Why does the warm air mass
slowly override the cold mass cause long periods
of rain?
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Stationary Front

• The air from the warm front and cold front meet,
  but do not move
• These fronts have similar weather conditions as
  warm fronts
• SYMBOL warm and cold fronts are moving in
  opposite directions, thus making a stationary
  condition

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Cross Section View look at the spread out,
horizontal stratus clouds
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Occluded Front

• Cold air catches up to and overtakes a warm front
  (often squeezing it between another cold front)
• May produce precipitation for many days
• SYMBOL cold and warm fronts mix hence the
  purple color - the bumps are also on the SAME
  SIDE OF THE LINE (sometimes just a mix of red
  blue symbols)

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Cross Sectional View
Overhead View On Map
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This is the jet stream. It moves from West to
East in the US and dictates what our weather will
be. What kind of air is being brought to NY
right now?
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LAKE EFFECT SNOW

• Great Lakes Region NYS
• cP air mass passes over the warmer more humid
  lake air causing it to rise rapidly and form into
  cumulonimbus clouds
• HEAVY snowfall occurs rapidly
• Western NYS is known as the SNOW CAPITAL of the
  USA!

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