All About Tornadoes

• A tornado is a violent rotating column of air extending from a thunderstorm to the ground.
• The most violent tornadoes can produce massive destruction with wind speeds of 250 mph or more. 
• Damage paths can be more than 1 mile wide and 50 miles wide.
• The typical tornado moves from southwest to northeast, but they have been known to move in any direction. The average forward speed of a tornado is 30 mph but it may vary from stationary to 70mph.

There are three basic ingredients necessary  for development of a tornado.

• Moist, unstable air at the surface.
• Cold air aloft.
• Change in wind direction and/or speed with height (Vertical wind shear)

What happens:

• Before thunderstorms develop, a change in wind direction along with an increase of 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. The area of rotation, 2-6 miles wide, now extends through much of the storm.
• This rotating column of air, known as a funnel extends from the cloud and grows downward toward the ground. Once the funnel touches the ground is becomes a tornado.
• Since the center of the funnel is a low pressure area, air rushes into the column and rises. The air is cooled as it rises and water vapor condenses to form the familiar funnel shaped cloud. As the rotating winds begin to pick up dirt and debris from the ground, the funnel will darken.
• The strongest tornadoes occur in supercell thunderstorms which can also produce large hail and strong downbursts.

Tornadoes are classified by wind speed and damage according to the Fujita Scale.

FUJITA WIND DAMAGE SCALE

Although tornadoes occur in many parts of the world, they are found most frequently in the United States east of the Rocky Mountains during the spring and summer months.

In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and over 1,500 injuries.

Even though tornadoes can occur in the United States anywhere at any time of the year,  there are certain areas that favor tornado formation at different times of the year.

• In the southern states peak tornado season is March through May when warm, moist gulf air mixes with the cooler air masses that extend into the south.
• In the northern states the peak tornado season is in the summer, when the warm, moist gulf air reaches farther north.
• In some areas along the Gulf Coast there is a second peak season in the fall.

• People in automobiles
• The elderly, very young, and the physically or mentally impaired
• People in mobile homes
• People who may not understand the warning due to a language barrier

In addition to keeping abreast of the latest watches and warnings issued by the NWS there are certain environmental clues that Mother Nature provides us with:

• Dark, often greenish sky
• Wall cloud
• Large hail
• Loud roar-similar to a freight train.

• Wxnet4 Tornado Page
• Tornadoes....Nature's Most Violent Storms, A Preparedness Guide published by NOAA and the American Red Cross.
• Storm Prediction Center
• Everything you want to know about tornadoes by USA Today
• Tornado myths
• Owlie Skywarn Weather Book Great for elementary school children.
• Are you ready for a tornado?