Which statement best describes an occluded front?

• A. A frontal occlusion occurs when a fast-moving cold front catches up with a slow moving warm front.
• B. A warm front overtakes a cold front.
• C. Two warm fronts merge.
• D. A stationary front.

Answer: (A)

Occluded fronts form when a fast-moving cold front catches up to and overtakes a slow-moving warm front, lifting the warm air off the surface and creating a single boundary where the cooler air wedges underneath the remaining warm air aloft. This is the scenario described by the statement that a fast-moving cold front catches up with a slow-moving warm front. The other descriptions don’t describe occlusion: a warm front overtaking a cold front isn’t how occlusions typically develop, merging two warm fronts doesn’t create an occluded boundary, and a stationary front involves no movement to produce occlusion.