Environmental Science 102
Weather Systems: Fronts and Cyclones


Air moves from high pressure to low pressure.
Air will continue to move until the pressures are equal.
The greater the pressure gradient (i.e. the greater the difference between two location's pressures) the greater the force of wind.

Major Global Wind Belts

Polar Easterlies
Polar Front
Prevailing Westerlies
Subtropical High Pressure Belt
Trade Winds
Intertropical Convergence Zone (ITC)

Coriolis Effect

Apparent force which causes free moving objects to appear to be deflected from its path of motion.
Cause by the rotation of the Earth
Northern Hemisphere:
Southern Hemisphere:

Low Pressure Centers

High Pressure Centers


Air Moves outward
Replaced by descending air
What happens to this air as it descends?


Air moves inward
Converging, rising air
What happens to this air as it rises?

Traveling Cyclones

Wave Cyclone - forms along the Polar Front in the mid- and high-latitudes.
Tropical Cyclones

Cold Front

Cold air mass moving into a zone occupied by a warm air mass
Cold Front Diagram

Warm Front

Warm air mass moving into a zone occupied by a cold air mass
Warm Front Diagram

Occluded Front

Cold Front overtakes a Warm Front
Occluded Front Diagram Stage 1
Occluded Front Diagram Stage 2

Dry Line

Dry air (cT) converges with moist air (mT).
Dry Line Diagram

Formation of a Wave Cyclone

Two large anticyclones from along the Polar Front
A low pressure trough develops between them where the winds converge.
Stationary Front forms
Low Pressure center develops.
Rotation causes the Cold Front to begin to move around the low pressure.
Cold Front overtakes the Warm Front.
Occluded Front forms.
Occluded Front breaks down.

Cyclonic Motion

Storm Tracks