Which statement best describes an occluded front?

• A. A fast-moving cold front overtakes a slower warm front and wedges beneath it.
• B. A warm front overtakes a cold front.
• C. The boundary remains stationary for an extended period.
• D. A boundary between warm, dry air and warm, moist air.

Answer: (A)

Occluded fronts form when a cold front overtakes a warm front. The faster-moving cold air undercuts the warm air, lifting it off the surface and causing the boundary to become a single, combined front. That’s why the description of a fast-moving cold front overtaking a slower warm front and wedging beneath it is the best fit. It captures the essential dynamic: cold air catching up and lifting the warm air, which is the defining feature of an occluded front.

The other scenarios describe different situations. If a warm front were to overtake a cold front, that’s not the typical interaction that creates an occlusion. A stationary boundary describes a front that isn’t moving, which is a different phenomenon. A boundary between warm, dry air and warm, moist air reflects a humidity contrast within warm air, not the occlusion process itself.