Thunderstorms and Tornadoes

1. Thunderstorms and Tornadoes By: Bisma Parvez, Teri-Lynn Gelinas, and Lydia Kim

2. What are Tornadoes? • A tornado is a violent windstorm characterized by a twisting, funnel-shaped cloud. • It is spawned by a thunderstorm (or sometimes as a result of a hurricane) and produced when cool air overrides a layer of warm air, forcing the warm air to rise rapidly.

3. How Tornadoes are Formed • Tornadoes are formed because thunderstorms usually contain updrafts, which are large rising swells of warm, moist air. • As the updraft moves, it rotates; if the rotation grows sufficiently intense, the storm can evolve into a tornado or funnel cloud

4. What Time of Year it Occurs • Tornado season is generally March through August, although tornadoes can occur at any time of year. • Most tornadoes occur during the mid afternoon to early evening. They can occur at anytime and without any warning.

5. Which Area is Most Common? • In the United States, most tornadoes occur in the area of Texas, Kansas, Nebraska, Iowa, and Oklahoma. This area is known as the Tornado Alley. • Canada's "tornado alleys" are southern Ontario, Alberta, southeastern Quebec, and a band stretching from southern Saskatchewan and Manitoba through to Thunder Bay.

6. Tornadoes in This Area • Windsor, Ontario- June 17, 1946; 17 dead, hundreds injured • Windsor, Ontario-April 3, 1974; 9 dead, 30 injured • Barrie, Ontario- May 31, 1985; 8 dead, 155 injured

7. Recent Tornadoes • November 10, 2002 8:50 PM CSTAbout one third of the town of Carbon Hill, Walker County, Alabama, was completely destroyed. At least 11 people were killed and 50 were injured. The tornado ripped through the very center of town. • November 10, 2002 7:45 PM CSTIn Lowndes County, Mississippi, one man was killed when a tornado threw his trailer 150 feet. The same tornado, or one in the same family, destroyed dozens of buildings at Columbus.

8. Recent Tornadoes Continued… • November 5, 2002 6:00 PM CSTA tornado disrupted the election process in Abbeville, Alabama. The funnel ripped apart homes, businesses, and the high school in the downtown area. One person died as a large tree crashed through the house. About 25 others were injured.

9. Potential for Destruction • Every tornado is a potential killer and may cause considerable damage. • The most violent tornadoes are capable of tremendous destruction with wind speeds of 250mph or more. • Damage paths can be in excess of one mile wide and 50 miles long.

10. Frequency • On average, there are about 850 tornadoes per year. • In 1973 & 1990 there were over 1100 tornadoes reported. • In Canada, during an average year, there are about 80 tornadoes.

12. Other Exciting Details • Tornadoes vary in size from a few hundred yards wide to over 20 miles. • Most rotate counter-clock-wise in the northern hemisphere and clockwise in the southern hemisphere because of the Coriolis effect. • Most move from southwest to northeast, however, their direction can be very erratic. The time a tornado spends on the ground may vary from a few minutes to many hours.

13. What are Thunderstorms • Thunderstorms are relatively small, organized parcels of warm and moist air that rise and produce lightning and thunder. They are one of Nature's frequent ways of balancing the amount of energy in the atmosphere - it is estimated that over 40,000 thunderstorms occur each day around the world. • a cumulonimbus cloud that reaches sufficient intensity to produce lightning and thunder.

14. The basic fuel is moisture (water vapour) in the lowest levels of the atmosphere. The air above the lowest levels has to cool off rapidly with height, so that 2-3 miles above the ground, it is very cold. Finally, we need something in the atmosphere to push that moist air from near the ground up to where the air around it is cold. This "something" could be a cold front or the boundary between where the cold air from one thunderstorm meets the air outside of the storm or anything else that forces the air at the ground together. How it Forms

15. The Time of Year it Occurs • The best time of year for a thunderstorm to occur is between September to March. • While most of the more violent storms occur in the spring and summer months, thunderstorms may develop at any time of the year.

16. Where it is Most Common • The Midwest and Great Plains regions of the U.S. average between 40 and 60 days of thunderstorms per year. These two regions are prone to some of the most severe thunderstorms on Earth. • Florida experiences an average of 90 days or more per year of thunderstorm activity. This is mostly due to the proximity to the Gulf of Mexico and the Atlantic Ocean, which provide an ample amount of warm, moist air.

17. Thunderstorms in Our Area • Tuesday July 23, 2002 - Thunderstorms in southern Ontario knocked down power lines and ruptured gas lines. • Severe thunderstorms, stretching from Barrie to Windsor, moved through southern Ontario on Monday July 22, 2002.

18. Potential For Destruction • Severe thunderstorms are really dangerous. They are capable of producing baseball sized hail, strong winds, intense rain, flash floods, and tornadoes. Severe thunderstorms can last several hours and grow 18km high.

19. Frequency • It’s estimated that 100,000 thunderstorms occur each year in the U.S. • World wide, the tropics produce by far the most thunderstorms. On a daily basis, about 44000 thunderstorms occur and about 2000 are in progress at any time.

20. Other Exciting Details • There are three stages describing the life cycle of an air-mass thunderstorm. • 1. cumulus • 2. mature • 3. dissipating • About 10% of the thunderstorms that occur each year in the United States are classified as severe. • They may appear different in colour and some may not be seen.

21. THEEND