On the Weather Channel you hear all about how a Cold Front is moving in and how there will be a lot of wind...etc. But does anyone know how the cold/wram fronts work? Where they originate? What causes them? Their effect?
In the simplest terms, a front is simply the imaginary boundary line between two distinct air masses. If a cold front is "moving in" on a region, it means that a mass of colder air is in the process of displacing a mass of warmer air, and vice versa. The usual reason for such movement is, almost by definition, wind. Wind, in turn, has a variety of causes.
In the temperate latitudes, the most commonplace are transient or semi-permanent pressure systems - Europeans, say, will be familiar with the "Icelandic Low" and "Azores High" as examples of the latter type. Air flow follows the density gradient, i.e. it streams into a low pressure system and out of a high pressure system. Because of the Coriolis_effect, the streamlines curl one way or the other, depending on the nature of the pressure system and the hemisphere, so instead of a simple sink or source one gets a vortex. Technically, these are known as (anti-)cyclones, just like the tropical storms with which that term is more closely associated in common usage - the basic mechanism is the same. If the cyclone picks up a cold air mass along its polarward edge and drags it along, around its Eastern or Western edge, we have a cold front moving equatorwards. Vice versa, if it picks up a warm air mass along its equatorward edge and drags that along, we have a warm front moving polarwards.