What Causes Thunderstorms?

12/3/2020 (Permalink)

Thunderstorms form when an air mass becomes so unstable that it overturns violently. "Unstable" means that the air in the lowest layers in unusually warm and humid, or that the upper layers are unusually cool, or oftentimes, both. Pockets of rising near surface air in an unstable air mass expand and cool, and as some of the water vapor present condenses into a cloud it releases heat, which then makes the air parcel even warmer, forcing it to rise still higher in the atmosphere. If the lower level air is sufficiently warm and humid, and the higher altitude air is sufficiently cool, this process continues until a tall convective cloud - the thunderstorm - is formed. The result can be a storm extending as high as 40,000 to 60,000 feet (8 to 12 miles). The upper portions of the storm, even in the warm tropics, are made of ice. About 50% of the rain reaching the surface in a thunderstorm originated as ice in the upper reaches of the storm.