Tornadoes, or twisters as they are often called, are violent storms that can rip paths of destruction through towns and cities and kill large numbers of people. Their characteristic funnel shapes look very dramatic in photographs and videos, though it is difficult and dangerous to get close enough to take these shots.
Tornadoes tend to occur more frequently in parts of the world such as the mid-western United States where weather patterns create the general set of conditions they need to form.
COPYRIGHT: BBC
More info on: http://www.bbc.co.uk/science/earth/natural_disasters/tornado