Transcript Weather Patterns PPT

What Causes Wind?
Air is a fluid – it moves easily
Movement of air caused by
changing air pressure
Wind is movement of air from high
pressure to low pressure
Air Movement
Global Winds
Types of Air Masses
 An air mass forms when a large amount of
air stays in the same place over an area
 Continental air masses form over land and
are dry
 Maritime air masses form over water and are
moist
 Polar air masses are cold
 Tropical air masses are warm
Types of Air Masses
 There 4 air masses affecting North America
 cT- continental tropical
 cP – continental polar
 mT – maritime tropical
 mP – maritime polar
Fronts
 Air masses move and bump into each other
 Fronts appear at the edges of two air masses
where they are colliding with each other
Fronts
There are 4 types of fronts:
Cold fronts
Stationary fronts
Warm fronts
Occluded fronts
Cold front
 Occurs when a cold air mass overtakes a
warm air mass
 Cold air forces warm air to rise quickly
 Resulting in strong winds, thunderstorms,
and large amounts of precipitation
Cold fronts usually bring cooler weather, clearing skies, and a sharp change in wind
direction.
http://www.suu.edu/faculty/colberg/hazards/weather/05_cnWfronts.html
Cold Front Diagrams
Warm Fronts
 Occurs when a warm air mass overtakes
a cold air mass
 Warm air slowly rises over the cold air
 Starts with steady rain (8-12 hours) but
eventually clears when temperatures
rise
 Warm fronts tend to move slowly are
far less violent then cold fronts
After warm front passes, weather becomes warm and humid, but generally clear
Warm Front
Warm Front Diagrams
Stationary Front
When neither air mass can move
the other
Similar to warm fronts and can
remain in same place days
Light wind and precipitation occur
across entire region affected
Occluded front
 When a warm air mass gets trapped between two cold
air masses
 Strong winds and heavy precipitation occur