How does a warm front form?

A warm front forms when a warm air mass rises over a colder air mass. This process occurs because warm air is less dense than cold air, allowing the warm air to gradually ascend over the cooler, denser air at the surface. As the warm air rises, it cools and can lead to cloud formation, precipitation, and other weather changes associated with fronts.

The rising of warm air over cold air typically results in stratiform clouds and steady precipitation, as the warm air cools at higher altitudes, causing moisture to condense. This mechanism is a critical component of weather systems and plays a significant role in orchestrating climatic changes across regions affected by different air masses.

Other descriptions in the question relate to different types of atmospheric phenomena. The interaction of cold air pushing under warm air describes a cold front rather than a warm front. Similarly, the collision of two air masses without any movement indicates a stationary front, while warm air trapped between two cold air masses describes an occluded front. Each of these processes involves different dynamics and outcomes in meteorology.