Explanation of Cumulus Stage
 
    Bubbles of warm air begin to develop close to the earth as the sunshine warms the surface. These bubbles of warm air are called thermals. As they become buoyant (less dense than the air above) they begin to rise. Therefore, vertical motions become a factor. as the air begin to rise the pressure and temperature begin to decrease with height. The thermals finally reach a point at which they become saturated causing condensation to occur. On the animation this occurs around the 1 kilometer (850 millibars) point, After this a cloud begins to grow as the updrafts continue to force warm muggy air upward.

    Another important factor is that when condensation occurs more heat is released into the atmosphere. This process continues to make the rising air more buoyant. This added heat can be seen on the animation by watching the isotherms (equal lines of temperature) bend upward as added heat being released due to condensation occurs. At the zero degree line around 4 kilometers (600 millibars) another interesting ingredient comes into play. The formation of ice crystals begin. This can be seen on the animation as light blue droplets within the cloud. This process transforms the cumulus cloud into a cumulonimbus cloud meaning the cloud is changing from a non-precipitating cloud to a precipitating cloud.

    In summary the cumulus stage is dominated by updrafts in the atmosphere. During this stage cumulus clouds form due to condensation and the process by which precipitation forms gets underway. During the next section a continuation of development will be displayed as we move into the Mature Stage of the thunderstorm development.

    Important features on the animation include:  1.)  Orange lines- Isotherms (equal lines of temperature), 2.) Numbers on the left hand side- Height of atmosphere in kilometers, and 3.) Numbers on the right hand side- Height of atmosphere in pressure.