An Occluded Front

An Occluded Front is a cold front that overtakes a warm front and the two fronts combine into one front. The chapter also explains how when it appears on a surface weather map that it is defined by a purple line that has alternating cold-front triangles and warm-front half circles, of which both figures run in the direction of the way the front is moving. There are two types of occluded fronts, the first is called a Cold Occlusion with the second being a Warm Occlusion.
A cold occlusion is a when there is a cold front that is moving much faster than the warm front that is ahead of it. When this happens the warm front and warm air mass are lifted up over the cold front which typically cause a shift in the clouds, and this starts with high clouds