Cold and Warm Fronts

A weather front is a boundary in between two masses of air of different densities and is the main cause of significant weather, such as storms. Some fronts produce no precipitation and little cloudiness, although there is usually a wind shift. The weather usually quickly clears after a front passes.

A cold front is a meteorological word that is used to describe the movement of a cooler air mass into an area of warmer air. The air with greater density (the cold air) moves under the less dense warmer air, lifting it, which can cause a line of showers and thunderstorms. Cold fronts can also move up to twice as fast as warm fronts.

300px-Warmfrontai.svg
Illustration of a front.

 

A warm front is a leading edge of an advancing mass of warm air. It separates warm air from the colder air above.

Warm fronts usually have stratus and cirrus clouds, but sometimes they also have cumulus and cumulonimbus clouds. Before the warm front passes, there can be rain or snow. While it is passing, there is often light rain or drizzle. Warm fronts move more slowly than cold fronts.

On a weather map, warm fronts are shown as red lines with red semicircles pointing in the direction that the front is moving. Cold fronts are shown in blue.

Images for kids

  • 337px-Unusually_well_defined_warm_front
    Approaching weather fronts are often visible from the ground, but are not always as well defined as this.

     

  • Airmassesorigin
    Different air masses which affect North America, as well as other continents, tend to be separated by frontal boundaries. In this illustration, the Arctic front separates Arctic from Polar air masses, while the Polar front separates Polar air from warm air masses. (cA is continental arctic; cP is continental polar; mP is maritime polar; cT is continental tropic; and mT is maritime tropic.)

     

  • DangerousShelfCloud
    A shelf cloud such as this one can be a sign that a squall is imminent

     

  • Konvektionsregen
    Convective precipitation