The negatively charged bottom of the cloud induces positive charge near ground. If the electrical field, caused by the different charge regions, becomes high enough, a lightning discharge may occur. What lightning is, how it works and which different types of lightning discharges may occur, are discussed in the about - lighting section . Facts about thunderstorms Thunderstorms have an average lifetime of 20 to 30 minutes. Their size varies from 5 to over 15 miles in diameter.
Atmospheric pressure changes near a thunderstorm.
The strong updrafts in a thunderstorm cause a small low-pressure area which sucks air in from around the thunderstorm. The air that exits out at the top of the storm causes an increase in pressure in the surroundings. Because thunderstorms are embedded deep in the atmosphere, look for strong vertically developed clouds. In practice, this means that you will have to look for large convective clouds and anvils as shown on the picture. On satelite pictures one can also find thunderstorms.