Lenticular and stratus clouds form when air is forced upward and the rising air cools rapidly. When warm air rises and moves over cooler air, any of the three major types of clouds, called stratus, cirrus or cumulus clouds, can form. When cold air forces warm air upward, the result is cumulus cloud formation. When air is warmed by the ground and begins to rise, the result can include the formation of cumulus, nimbus, mammatus and stratocumulus clouds.
The type of clouds that form when warm and cold air masses meet can vary based on the geographical features of the region, the precise temperature of the air masses and the altitude of the clouds. For instance, cirrus clouds are thin clouds located at an altitude of 20,000 feet or higher. Cirrus clouds are often present directly before stormy or other changing weather.
When warm air is located directly over cold air, altostratus, altocumulus and nimbostratus clouds form at altitudes of 6,000 to 20,000 feet, and the clouds cause the sky to appear gray. Stratus, cumulus and stratocumulus clouds are formed when cold air forces warmer air upward. Large storm clouds, called cumulonimbus clouds, can reach up to 60,000 feet high and are formed when air near the ground is heated and rises into cold air.