We know that cold fronts bring cooler air and warm fronts bring warmer air, but what exactly is a front?
The word front is used interchangeably with frontal zone, frontal surface, and a surface front. Typically, when used in broadcasting, a front refers to the area where a frontal zone meets the earth’s surface. Imagine two different air masses, one with colder air and one with warmer air, sitting next to each other. Actually, it might be easier to imagine a red balloon and a blue balloon in contact with each other. The area where the balloons are touching would be the frontal zone. If you could set that area perpendicular to a table, you could imagine the surface front where the touching parts of the balloons meet the table.
Fronts don’t have to be just about temperature differences between air masses, but it happens to be the easiest way to define them since temperature is linked to density. Other ways to recognize a frontal zone include a pronounced dip in barometric pressure along the boundary, a change in wind direction, and a difference in moisture content.
The frontal zone is where more exciting weather can happen. Clouds, rain, and severe storms usually occur along frontal zones. The words used to describe a front such as warm or cold really describe the air mass following it. If a frontal zone moves from north to south and brings colder air, it’s a cold front. If the same frontal zone moves from south to north and brings warmer air, it’s a warm front. If it stalls and generally stays put over one area, it’s a stationary front. An occluded front is one that gets cut off from the rest of a frontal system and forms as a cyclone – a counter-clockwise circulation of air.