n.
Violent, low-pressure storm, relatively small in diameter but with very rapidly rotating winds and an intense updraft near the centre.
The relatively low pressure at the centre of a tornado's funnel-like vortex causes cooling and condensation, making the storm visible as a revolving column of cloud, called the funnel. Tornadoes normally travel at 3040 mph (5065 kph). The winds around the vortex average nearly 300 mph (500 kph) and have been known to reach 500 mph (800 kph). Tornadoes often occur in groups.