A tornado is a violently rotating column of air that is in contact with the ground. Tornadoes take different forms, some are large and ominous, while others are relatively small and may be difficult to see.
Waterspouts are weak tornadoes that occur over water.
In some areas, especially along the Front Range of the Rocky Mountains and in the High Plains, tornadoes from during the early stage of rapidly developing thunderstorms and often appear nearly transparent until dust and debris are picked up by the winds.