What do cumulonimbus clouds look like and how do they form?

During this stage, updrafts and a downdrafts are present and the thunderstorm is at its most intense state. The cloud grows so high, that it reaches a stable part of the atmosphere (possibly the stratosphere) and cannot grow any higher. The top of the cloud spreads out and forms an anvil shape. read more

Believe me when I say this, cumulonimbus clouds, especially the ones at mid afternoon/ late evening, always give a threatful feeling to cloudspotters, more importantly to gliders, parachutists and pilots, because of their massiveness and potential. read more