polar front

An imaginary line where polar and tropically-derived air masses converge and interact. It marks the meeting zone of the subtropical anticyclones and the outflows of cold air from the polar anticyclones. It is located around 50-55º of latitude in summer and 35-40º in winter, in both hemispheres. It presents large undulations, around which the frontal low-pressure systems responsible for the changeable weather characterizing mid-latitudes originate. Above it flows the polar jet stream.