In a nutshell, warm, moist, high velocity rising air in a sufficiently large volume creates a thunderstorm. The fuel for all storms is warm, moist air present near the Earth’s surface. If the atmosphere around the cloud is unstable, meaning it cools faster with increasing height than the ascending cloud, then the parcel of air containing the cloud is said to be buoyant. Just like an inflated beach ball that has been submerged under water, it will rise quickly to the top. As the cloud parcel rises, latent heat is released from the condensation of water vapor. The latent heat releases more energy into the parcel helping to increase its upward velocity. This process creates a column of rapidly rising air known as an updraft. Ultimately, it is this updraft that feeds a thunderstorm. A thunderstorm will last as long as a supply of warm and moist air is available.
Thunderstorms don’t always develop despite having an abundance of warm and moist air though. That is because a trigger is necessary to get the air rising in the first place. This trigger can be a large thermal created by lots of sunshine during the heat of the day, or the upward motion produced by fronts pushing air together.
A thunderstorm can extend several miles above the surface of the Earth. Because temperatures drop as you move up in the atmosphere, the tops of thunderstorms are made of ice. It is this complex mixture of water, ice and high velocity air currents that create the electric field in a storm. Strong electric charges build up between different parts of the thunderstorm as well as the ground below. This results in the phenomenon we know as lightning.
The energy in even a modest thunderstorm can be impressive. A 20-minute thunderstorm is said to produce about 100,000,000,000 watts of energy. That is more energy than was released from the atomic bomb dropped on Hiroshima.