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Weather. Part 5: Weather Patterns. Air Masses. Large bodies of air Movement of them causes changes in weather Cover thousands of square kilometers Properties fairly uniform Classified by where they form. Continental – form over continents; relatively dry

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weather

Weather

Part 5: Weather Patterns

air masses
Air Masses
  • Large bodies of air
  • Movement of them causes changes in weather
  • Cover thousands of square kilometers
  • Properties fairly uniform
  • Classified by where they form
  • Continental – form over continents; relatively dry
  • Maritime – form over oceans; relatively humid
  • Polar – cold
  • Tropical - warm
4 major air mass types in usa
4 Major Air Mass Types in USA

1. Maritime tropical –

  • Forms over ocean near the equator
  • Warm, moist air
  • Most commonly affects Eastern states
  • In summer brings hot, humid weather
  • In winter brings rain or snow if it encounters a cold air mass
4 major air mass types in usa1
4 Major Air Mass Types in USA

2. Maritime polar –

  • Forms over northern Atlantic and northern Pacific oceans
  • Cool, moist air
  • Bring cloudy, damp weather to Northeast and Pacific Northwest
4 major air mass types in usa2
4 Major Air Mass Types in USA

3. Continental tropical –

  • Hot and very dry
  • Forms over the desert southwest and Mexico usually during summer
  • Affects southwest states, plains, and Mississippi valley and can bring record high temperatures
4 major air mass types in usa3
4 Major Air Mass Types in USA

4. Continental polar –

  • Cold and dry
  • Forms over Canada
  • Often dominant weather in winter
  • Brings very cold weather
  • Can also bring clear, pleasant weather to the North in summer
major air mass types
Major Air Mass Types
  • mT = Maritime Tropical
  • mP = Maritime Polar
  • cT = Continental Tropical
  • cP = Continental Polar

cA = Continental Arctic (5th type)

Brings extremely cold temperatures with very

little moisture, originate north of the arctic circle in winter

fronts
Fronts
  • A front is a boundary that forms when two air masses with different properties meet
  • Weather is usually unsettled and stormy along a front.

4 types of fronts:

  • Cold
  • Warm
  • Occluded
  • Stationary
cold front
Cold Front
  • Cold air mass meets and pushes under a warm air mass
  • Pushes warm air up
  • Can cause violent storms
  • Fair, cool weather usually follows a cold front
  • Generally move northwest to southeast
  • Can cause a rapid drop in temperature of more than 15° in one hour
cold front1
Cold Front
  • Weather symbol: blue triangles point in the direction the cold front is moving

http://commons.wikimedia.org/wiki/File:Example_of_a_cold_front.svg

warm front
Warm Front
  • Warm air overtakes cold air and goes over it
  • Showers followed by hot, humid weather
  • Noticeably warmer after the front passes
  • Generally move southwest to northeast
warm front1
Warm Front
  • Weather symbol: Red, semicircles pointing in the direction the warm front is moving

http://commons.wikimedia.org/wiki/File:Example_of_a_warm_front.svg

occluded front
Occluded Front
  • A cold front moves faster than a warm front
  • When a cold front overtakes a warm front an occluded front forms
  • Usually form around low pressure areas
  • At the occluded front the cold air mass meets the cool air mass that was ahead of the warm front
  • Warm air rises to form cumulonimbus or nimbostratus clouds bringing precipitation
occluded front1
Occluded Front
  • Weather symbol: purple, alternating triangles and semicircles pointing in the direction the front is moving

https://commons.wikimedia.org/wiki/File:Occluded_cyclone.svg

http://commons.wikimedia.org/wiki/File:Occlusiefront.png

stationary front
Stationary Front
  • When warm air meets cold air and no movement occurs
  • Rain may fall for many days
  • Weather Symbol: Alternating blue triangles pointing towards the warmer air and red semicircles pointing towards the colder air
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