Polar front

[1] 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 and stays stable.

[2] 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 extratropical cyclones form on boundaries between warm and cold air.

[3] In winter, the polar front shifts towards the Equator, whereas high pressure systems dominate more in the summer.