This paper discusses tornadoes: Description, impact, susceptible areas, causes and forecasting.
The typical tornado has ground contact for about six miles, marking a path up to 500 feet wide. Tornadoes travel as fast as 35 to 60 miles per hour. The average number of tornadoes in the United States ranges between 700 and 800 per year, exceeding 1,000 in some years 1973, 1982, 1990, and 1992. Tornadoes occur most frequently in Texas, followed by Oklahoma and Kansas. Tornadoes have been observed in every continent except Antarctica. Most tornadoes occur in the United States but other areas that often experience tornadoes include New Zealand, western and southeastern Australia, south-central Canada, northwestern and central Europe, Italy, south-central and eastern Asia, east-central South America, and Southern Africa. There are many different sizes and styles of tornadoes. The wedge tornado is the most typical type of tornado and is straight on the sides, has a wide damage path and is usually as wide as it is tall.