What is "polar front"

n. the front of an advancing mass of colder air [syn: cold front]

In meteorology, the polar front is the boundary between the polar cell and the Ferrel cell in each hemisphere. At this boundary a sharp gradient in temperature occurs between these two air masses, each at very different temperatures.

The polar front arises as a result of cold polar air meeting warm tropical air. It is a stationary front as the air masses are not moving against each other. Off the coast of eastern North America, especially in winter, there is a sharp temperature gradient between the snow-covered land and the warm offshore currents.

The polar front theory says that mid-latitude cyclones form on boundaries between warm and cold air. In winter, the polar front shifts towards the Equator, whereas high pressure systems dominate more in the summer.