One of the most terrifying weather events is a fully developed tornado. The strong air currents within a storm cloud can create a high speed vortex (spiral) or funnel of winds. Wherever the end of the vortex touches the ground it creates a path of concentrated destruction that has no equal in nature. Near the core of a tornado, winds may spiral around at more than 480 km/h (300 mph).

Tornadoes develop near the boundary between the upcurrents and downdraughts in a storm cloud. A 'funnel cloud' develops first from the cloud base and this may then extend down to ground level. 'Waterspouts' are simply tornadoes that form over water rather than land. They tend to lose their energy as soon as they cross from water to land. Waterspouts are usually confined to shallow waters during warmer seasons.The destruction caused by tornadoes is due mainly to the violence of the winds. There is very low pressure at the centre of the vortex. If a tornado goes over a building it can explode outwards because of the sudden drop in pressure as the vortex passes over the building. Although they are usually less than 250 m across, they can travel a long way, sometimes more than 200 km (125 miles) across the land surface. They pick up material from the ground as they go, including cows, cats, dogs and other animals - including humans! They can be the source of some very strange weather indeed! Find out more about tornado chasers, and how you can protect yourself from severe weather.