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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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