Weather Patterns and Severe Storms Ch. 20. air mass. a large body of air that has the same temperature and humidity throughout classified according to where they originate
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•as it moves, the characteristics of an air mass change and so does the weather in the area over which the air mass moves.
Air Masses Are Classified by Region
Originates over the ocean
humid air mass (m) (maritime)
Originates over the land
dry air mass (c) (continental)
Originates in cold air
cool air mass(P) (Polar)
Originates in warm air
warm air mass (T) (Tropical)
Which one affects us?
View satellite movies of air masses moving acrossNorth America.
small balloon carried observatory that carries a radio transmitter that sends out signals about air pressure, temperature, and humidity
fronts: boundary between two air masses having different temperatures and humidity
Types of Fronts
Compare and contrast warm and cold fronts.
the flow of air on either side of the front is neither toward the cold air mass nor toward the warm air mass, but almost parallel to the line of the front- the surface position of the front does not move
Observe an animation of a thunderstorm.
Two groups of thunderstorms:
All thunderstorms produce lightning!
a narrow, funnel-shaped column of spiral winds that extends downward from the cloud base and touches the ground
funnel is a mixture of clouds and dust
pressure gets lower in center
air flows toward the funnel and cools to dew point- drops form
lowering of condensation level due to low pressure causes cloud to funnel
Extremely low pressure-when it touches ground, acts like a giant vacuum
Waterspout: tornados over the water- weaker than tornados
Tornados usually occur during spring and summer and most likely occur in late afternoon
Fujita Scale: scale used for categorizing tornados