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Weather Systems
Section 12.2
Global Wind Systems
Earth rotates from West to East
 The direction of Earth’s winds are
influenced by rotation
 Coriolis effect is the movement of fluids
and objects in a curved path and not a
straight line
 Curves right in the North and Left in the
South

Global Wind Systems
Global wind systems result from heat
imbalance and the Coriolis effect
 They equalize thermal energy on Earth
 3 basic wind systems:

Polar Easterlies
 Prevailing Westerlies
 Trade Winds

Polar Easterlies
60 N latitude and north pole
 60 S latitude and south pole
 Cold winds
 Weak and sporadic
 Polar fronts are areas of stormy weather

Prevailing Westerlies
30 N – 60 N
 30 S – 60 S
 Originate in the west
 Steady winds that move most weather
across the U.S. and Canada

Trade Winds
30 N – 30 S
 Two circulation belts
 Air sinks, warms, and moves toward the
equator in an easterly direction
 Once at the equator it moves back north
and south
 Describe the horse latitudes and the Intertropical convergence zone

Trade Winds
Horse Latitudes – Near 30 N and 30 S
latitude; area of high pressure causing
weak surface winds
 Inter-tropical Convergence Zone – Near
equator; low pressure regions; forms
bands of cloudiness and storms to deliver
moisture to rain forests

Jet Streams
A jet stream is a narrow band of fast
westerly wind; the strongest core of winds
 Polar jet streams
 Subtropical jet streams
 Weather systems usually follow the path of
the jet streams

Fronts

4 types of fronts:
Cold
 Warm
 Stationary
 Occluded


Follow directions on page 313 to create
the Foldable study organizer.
Pressure Systems
Air always flows from an area of high
pressure to an area of low pressure
 Low-pressure systems are associated with
cloudy weather and precipitation; air rises;
counter-clockwise movement
 High-pressure systems are associated
with fair weather; air sinks; clockwise
movement
