Rising convectively, a cumulus cloud is the most common.
when the temperature of the rising air falls below the dew point
Rising hot air and water condensing out of that air.
Air and water form a cloud.
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.
Startus
Cumulus cloud.
when the temperature of the rising air falls below the dew point
This is a tornado.
tornado
A tornado
It depends on the temperature of the air around the cloud. A cumulus cloud is formed by warm air rising into a layer of cooler air, so the base of the cloud will be warmer and the air will get colder toward the top of the cloud. If water vapor condenses out of the air as it rises in the cloud, this will warm up the air in the middle of the cloud.
A vortex is form when the whirling motion of the cloud vortex results from a rapid downdraft of cold air replacing rising hot air.
Rising hot air and water condensing out of that air.
The heat from condensation makes the rising air warmer and stay less dense than the air around it.
When the rising warm air reaches it's dew point, the water vapor in the air condenses and forms cumulus clouds. If the atmosphere is extremely unstable, the warm air will continue to rise, which causes the cloud to grow in to a dark, cumulonimbus cloud. This cloud is a thunderstorm cloud.
tornado
Heat from the sun