Tornadoes

What is a tornado?

A violent rotating column of air extending from a thunderstorm to the ground.

Some tornadoes are capable of horrible destruction with wind speeds of up to 300mph.

They can destroy large buildings, uproot trees and throw vehicles hundreds of yards.

In an average year, 1000 tornadoes are reported nationwide.

How do tornadoes form?

Most tornadoes form from thunderstorms. Warm, moist air from the Gulf of Mexico

meets cool, dry air from Canada. This creates instability in the atmosphere.

Wind changes direction and speed. This causes a spinning effect close to the ground.

Rising air rotates the spinning winds from horizontal to vertical.

http://esminfo.prenhall.com/science/geoanimations/animations/Tornadoes.html

What is a funnel cloud?

A rotating cone-shaped column of air pointing down from the base of a thunderstorm, but not touching the ground.

When it reaches the ground it is called a tornado

When do most tornadoes occur?

Tornadoes can happen at any time of the year and at any time of the day.

In the southern states, tornado season is from March through May. A few southern states have more tornadoes in the fall

Tornado season in the northern states is during the summer.

Tornadoes are most likely to occur between 3 p.m. and 9 p.m.

Where do most tornadoes occur?

The central part of the United States, known as the Great Plains, has all the right “ingredients” for tornadoes.

More than 500 tornadoes typically occur in this area every year

It is called "Tornado Alley"

Tornado Alley

Tornado Scale

F-0: 40-72 mph, chimney damage, tree branches brokenF-1: 73-112 mph, mobile homes pushed off foundation or overturnedF-2: 113-157 mph, considerable damage, mobile homes demolished, trees uprootedF-3: 158-205 mph, roofs and walls torn down, trains overturned, cars thrownF-4: 207-260 mph, well-constructed walls leveledF-5: 261-318 mph, homes lifted off foundation and carried considerable distances, autos thrown as far as 100 meters

Effects of Tornadoes