What is causing a thunderstorm?

Air Mass Thunderstorm

The air mass thunderstorm is common in Florida. As with all thunderstorms, it contains thunder and therefore has lightning. The air mass thunderstorm lasts approximately one hour and has a very distinctive life cycle.
Cumulus Stage: Rising air, or updraft, cools and forms the cloud. The rising air is occurring in an environment that is favorable for convection. Lifting mechanism include solar heating or convergence from a sea breeze. It is not raining during this stage of the thunderstorm.
Mature Stage: As the cloud continues to grow, precipitation particles form and fall from the cloud. The precipitation falls into the updraft. The falling particles drag air down with them. This sinking air is referred to as downdrafts. Entrainment into the downdraft results in some evaporation of the precipitation, which causes a cooling which makes the air more dense, thus increasing the downdraft. Rain begins to reach the surface. Hail may also make it to the surface, but they are not very large.
Dissipating Stage: When the downdrafts encompass the storm, the updrafts are shut off and the storm begins to die. The intensity of the rain decreases.
Prior to the development of a thunderstorm, the air near the surface is often warm and moist. With the downdrafts come cool air and the temperature at the surface drops. After the storm passes, the temperature may begin to rise again.

Severe Thunderstorm

In the air mass thunderstorm the precipitation falls into the updraft, cutting off the storm's moisture supply and eventually kills itself. The air mass thunderstorm only lasts about an hour which is not enough time to produce severe weather. In the Severe thunderstorm the updrafts and downdrafts are separate from one another, This allows the storm to last longer and severe weather may develop. To separate the updraft from the downdraft requires wind shear.
Winds speed increase with altitude case to updraft to tilt. Because it tilts, when precipitation falls, it does not fall into the updraft, thus allowing a continuous source of moist warm air to fuel the storm. In addition to the winds increasing with altitude, the wind direction also changes. Enormous severe storms that develop and have a tilted updraft are calledsupercell thunderstorms.
Below are some animations of the updraft and downdrafts in a supercell thunderstorm. As you view these animations keep track of the following features: The overshooting top, the cirrus anvil, the updrafts (yellow lines) and a downdraft (green lines).