Atmosphere Contents

6. Secondary Circulation

Extra-tropical cyclones (mid-latitude depression systems) are areas of low pressure

Polar front theory has been developed as a working model of the development of mid-latitude cyclones (or depressions). The development of a cyclone, according to the model, occurs along the polar front (the semi-continuous boundary separating cold polar air and subtropical air). On a weather map the cycle of its formation and dissipation looks similar to that of a water wave rising and falling in the sea. The analogy of such a wave is often used to describe the movement of fronts through the various stages of the life cycle of a cyclone, a process which can last from a few days to over a week.

What are the stages of the life cycle of a cyclone?