How does the Cumulonimbus cloud form in a tornado?

Cumilonimbus clouds do not form in tornadoes; tornadoes formin in cumulonimbus clouds. A cumulonimbus cloud forms when a warm, moist pocket of air rises and the moisture in it condenses, releasing heat that keeps the air rising. This is what drives any thunderstorm. Under the right conditions, the storm my start to rotate, and this rotation may eventually lead to the formation of a tornado.