A tornado is a violently rotating column of air touching the ground, usually attached to the base of a thunderstorm.
A tornado forms when a rotating updraft within a severe thunderstorm, typically a supercell, develops a strong enough rotation to extend a column of air from the cloud to the ground, usually occurring when warm, moist air collides with cooler, dry air, creating wind shear that causes the air to spin vertically; this spinning motion intensifies as it descends, forming a tornado.Â