The Polar Front Part 1: Warm And Cold Fronts

We’ve all heard the meteorologist on TV or the radio talk about warm fronts and cold fronts. They bring clouds, rain, snow, and a change in temperature. Some people might even be able to tell you that cold fronts have heavier precipitation for a short time and warm fronts have lighter, steadier precipitation for a longer time. But how do these fronts form? Where do they come from? Where do they go to?

According to the polar front theory, developed by two Scandinavian meteorologists around the time of WWI, there is one long mostly continuous boundary between cold polar air and warm subtropical air that goes all the way around the world. It’s called, you guessed it, the polar front! For this discussion, we’ll just look at the northern hemisphere, but there’s also one mirroring it in the southern hemisphere. Just about all warm and cold fronts in the US during the winter are actually part of the polar front. (During the summer, the polar front retreats further north, hanging out in Canada.) How do we tell warm and cold fronts apart? By which air mass is dominant. If the cold air is dominant and is pushing the warm air out of the way, it’s a cold front. If the warm air is dominant, pushing the cold air out of the way, it’s a warm front.

This boundary isn’t a straight line; it can be bent or warped by wind. This is what happens with low pressure systems. The air rotating around them causes the boundary to move, pushing north on the east side of the system and south on the west side of the system. Though the front can be pushed hundreds of miles, it still remains continuous around the world. The front that brings plummeting temperatures to you in January is doing the same thing in Siberia.

Written by Scott Wolff