The plot device of the Wizard of Oz is a TORNADO. A TORNADO is a violent, rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris. They are often referred to as twisters or cyclones, although the word cyclone is used in meteorology to name any closed low pressure circulation.