What is an occlude?

Answer 1

A cold front normally moves at twice the speed of a warm front. An occluded front forms when a cold front catches up with a warm front. Occluded fronts are of two types:1. Cold occlusion : If the airmass of the advancing cold front is colder than the cool airmass of the warm front, the advancing cold front undercuts and lifts both the warm and cool airmass of the warm front. The weather is initially warm front type but during the passage of front, showery weather of cold front occurs. This occlusion is common in summer.

2. Warm occlusion : When the airmass behind the advancing cold front is less colder (cool) than the cold airmass of the warm front ahead, the advancing cold front overrides the warm front ahead. The weather in such a case is similar to that of warm front. This type of occlusion occurs in winters and is less common.