<AREA SHAPE=RECT COORDS="3,157,17,173" HREF="!In a cold front, the edge of a mass of cold air moves under a mass of warm air. A cold front often brings periods of heavy precipitation. The passing of the front brings colder weather.">
<AREA SHAPE=RECT COORDS="322,158,337,172" HREF="!In a warm front, the edge of a mass of warm air moves over a mass of cold air. Warm fronts often produce light, steady precipitation. The passing of a warm front brings warmer weather.">
A <I>front</I> forms when a cold air mass and a warm air mass meet. The main types of fronts are <I>cold fronts</I> and <I>warm fronts.</I> Cold fronts travel faster than warm fronts. When a cold front catches up to a warm front, an <I>occluded front</I> develops--either a <I>cold-front occlusion</I> or a <I>warm-front occlusion.</I><NP>
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World Book diagrams by Zorica Dabich</P>
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