What weather phenomenon occurs when a warm air mass is sandwiched between two cold air masses?

The phenomenon that occurs when a warm air mass is sandwiched between two cold air masses is referred to as an occluded front. In this situation, the cold air masses on either side of the warm air force the warm air to rise. The rising of the warm air can lead to cloud formation and precipitation, often resulting in significant weather changes.

An occluded front typically forms during the process of mid-latitude cyclones, where the colder air mass moves faster than the warmer air mass, lifting the warm air off the ground. This process can create complex weather patterns, including thunderstorms and varying types of precipitation. Understanding this mechanism is essential for predicting weather changes and patterns associated with occluded fronts.

The other options—cold fronts, warm fronts, and stationary fronts—describe different interactions of air masses and do not accurately capture the specific scenario of a warm air mass being positioned between two colder ones.