Weather

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Chapter 20 Weather Storms
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Air Masses Weather

• Air Masses
• A large body of air with the same temperature and
  amount of moisture at any altitude

• Movement of Air Masses
• As it moves, the characteristics of an air mass
  change and so does the weather in the area over
  which the air mass moves.

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Tornado DamageThe force of wind during a tornado
in Kansas was strong enough to drive this metal
into a utility pole!
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Classifying Air Masses

• Air masses are classified according to the
  surface over which they form

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Good
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Weather in North America

• Much of the weather in North America, especially
  weather east of the Rocky Mountains, is
  influenced by continental polar (cP) and maritime
  tropical (mT) air masses.

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Weather in North America

• Continental Polar Air Masses
• (cP) cool/dry

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Weather in North America

• Maritime Tropical Air Masses
• mT warm/wet
• Warm, loaded with moisture, and usually unstable.
• The source most precipitation received in the
  eastern two-thirds of the United States.

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Weather in North America

• Maritime Polar Air Masses
• (mP) wet/cool
• Begin as cP air masses in Siberia. The cold, dry
  air changes into mild, humid, unstable air during
  its long journey across the North Pacific.
• They also originate in the North Atlantic off the
  coast of eastern Canada.

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Formation of a Maritime Polar
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Weather in North America

• Continental Tropical Air Masses
• (cT) dry/warm
• Only occasionally do cT air masses affect the
  weather outside their source regions.
• In the summer - extremely hot, drought-like
  conditions in the Great Plains.
• In the fall - mild weather in the Great Lakes
  region, often called Indian summer.

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Quick Review!

• What kind of air would you expect to find in a mT
  air mass?
• 2. Which two air masses influence MOST of our
  weather in North America?
• 3. List the TWO defining features of an air mass?

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Answers

• What kind of air would you expect to find in a mT
  air mass?
• moist and warm
• 2. Which two air masses influence MOST of our
  weather in North America?
• cP and mT
• 3. List the TWO defining features of an air mass?
  
• Consistent temperature and moisture throughout