You have probably seen weather maps online or on TV. Weather maps are marked with Hs and Ls, which indicate high and low pressure centers. Usually surrounding these “highs” and “lows” are lines called isobars. Isobars are lines that show equal pressure.
The boundaries between different air masses are called fronts. Fronts can be found in three different ways. Winds often “converge” or come together at the fronts. Also, temperature differences can be quite noticeable from one side of a front to the other side. Finally, the pressure on either side of a front can vary significantly.
There are four different kinds of fronts you may see on a weather map. The most basic ones are the cold and warm fronts.
Cold fronts are depicted by a blue line with triangles pointed in the direction of motion. Cold fronts divide the leading edge of a cold air mass replacing a warmer air mass. Cold fronts nearly always extend anywhere from a south direction to a west direction from the center of low pressure areas.
A warm front is depicted by a red line with half-moons located on the side of the direction of its motion. A warm front is the leading edge of a relatively warmer air mass replacing a colder air mass. Like a cold front, warm fronts also extend from the center of low pressure areas but nearly always on the east side of the low.
If the front is essentially not moving, it is called a stationary front. Stationary fronts are depicted by an alternating red and blue line with a triangle on the blue portion and half-moon on the opposite side of the red portion of the line.
Cold fronts typically move faster than warm fronts, so in time they can “catch up” to warm fronts. When they do, the air is colder and denser. This is called an occluded front and they are indicated by a purple line with alternating triangles and half-moons on the side of its motion.
Now you know how to read a weather map! Find weather maps and more information on the weather at weather.gov.
