The 3-Dimensional Front

Over the past few days we have talked extensively about air masses.

The leading edge of these air masses are often where you find a front.

A front is simply a transition zone between two different air masses.

More specifically, it is a transition zone between air masses with different densities.

And since density differs between hot and cold air, we are talking air masses with different temperatures.

Along with temperature, we often find a difference in moisture too.

Now here is where things can get tricky. To wrap your brain around a full degree in meteorology, you eventually reach a point in the coursework where you have to start thinking in 3-D.

So picture in your mind a big, cold air mass moving south from Canada.

On the weather map you see on television, the leading edge of this air mass will be noted by a cold front.

So now pretend you are standing in your yard looking north and you can actually see this cold front moving toward you, evident by the line of clouds and sometimes by the dust the winds kick up out ahead of it.

Once it reaches you, look up -- the cold front also extends up into the atmosphere.

This is why you have to picture weather in 3-D.

This upward extension of the cold front is called a frontal surface, or frontal zone.

The frontal system not only extends out horizontally along the surface, but also vertically up into the sky.

Tomorrow we'll talk more about different types of fronts.