3. 1.Tornadoes are the most destructive of all weather- related events. 2. On average, a tornado's path is 2 miles long and 100 yards wide but can be as long as 10 miles and as much as a mile wide.

4. 3.The average tornado travels at a speed of 25 to 40 mph. 4.Winds inside a tornado can swirl at close to 300 mph.

5. 5. Most tornadoes occur between 8 pm and midnight. 6. Tornadoes occur throughout the world; however, the greatest number of tornadoes and most intense tornadoes occur in the United States.

6. 7. All tornadoes occur during the months of April, May, and June. 8. Tornadoes stay on the ground for an average of twelve minutes; however, a tornado can touch down several times.

7. 9. Tornadoes most frequently form in Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Louisiana, Mississippi, Missouri, Nebraska, Oklahoma, South Dakota, and Texas. 10. Most tornadoes move from northwest to southeast.

8. 11. Only 2 percent of tornadoes cause 70 percent of tornado-related deaths. 12. On average, 100 people are killed by tornadoes each year.

10. WHAT IS A TORNADO? The National Weather Service defines a tornado as "a violently rotating column of air pendant from a thunderstorm cloud and touching the ground." Each year, about 100,000 thunderstorms form over the United States. In an average year, between 600 and 1,000 of those thunderstorms generate tornadoes.

11. Go to www.teachersdomain.org for video clipwww.teachersdomain.org

12. TORNADO CHASER VIDEO Discussion Questions What is a tornado? How does it cause damage? Look at the tornado damage shown in the video. Why do you think some buildings are standing while buildings right next door to them are severely damaged or totally demolished? What are some characteristics of tornadoes that you can observe looking at the video?

13. Go To: http://www.usatoday.com/weather/graphics/tornadoes/fla sh.htm http://www.usatoday.com/weather/graphics/tornadoes/fla sh.htm to see how tornadoes form.

14. Thunderstorms form- winds move horizontally.

15. How Do Tornadoes Form? An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation. Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical. Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical. Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.

16. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation

21. HOW ARE TORNADOES MEASURED? EF-0 Light damageWind 65 to 85 mph Causes some damage to siding and shingles EF-1 Moderate damage Wind 86 to 110 mph Considerable roof damage. Winds can uproot trees and overturn single-wide mobile homes. Flagpoles bend. EF-2 Considerable damage Wind 111 to 135 mph Most single-wide mobile homes destroyed. Permanent homes can shift off foundation. Flagpoles collapse. Softwood trees debarked. EF-3 Severe damageWind 136 to 165 mph Hardwood trees debarked. All but small portions of houses destroyed. EF-4 Devastating damage Wind 166 to 200 mph Complete destruction of well-built residences, large sections of school buildings. EF-5 Incredible damage Wind above 200 mph Significant structural deformation of mid- and high-rise buildings.