In meteorology, an occluded front forms when a warm front is overtaken by a cold front. The cold air behind hits the cool air in front of the warm front and the lighter warm air in between is lifted completely off the ground. These form near the low pressure area at the north (in the northern hemisphere)end of the front and are often associated with rather heavy rain, although they may indicate that the storm itself is near the end of its life cycle. Occluded fronts are indicated on weather maps as a purple line with both triangles and half-circles pointed towards the direction the front is moving.