How is an occluded front formed?

An occluded front is formed specifically when a warm air mass is lifted off the ground by the encroachment of two colder air masses. This typically happens during the progression of a mid-latitude cyclone. As the colder air masses move towards each other, they can push the warm air mass upward since cold air is denser than warm air.

This leads to the warm air being "trapped" between the two colder air masses, creating an occluded front. The occlusion can result in a variety of weather phenomena, including precipitation, as the warm air cools and condenses. Understanding this concept is crucial for predicting changes in weather patterns associated with occluded fronts.

Other options fail to define an occluded front accurately. For instance, the behavior of air masses in the presence of temperature equalization or alternating patterns does not lead to an occlusion of any warm air. Such options misrepresent the dynamics of air mass interactions and their resulting fronts.