Although tornadoes occur in many parts of the world, these destructive forces of nature 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. A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 MPH or more. Damage paths can be in excess of one mile wide and 50 miles long. Once a tornado in Broken Bow, Oklahoma carried a motel sign 30 miles and dropped it in Arkansas!

What causes tornadoes?

Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather. Several states may be affected by numerous severe thunderstorms and tornadoes.

During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.
 

Tornado Variations

• Some tornadoes may form during the early stages of rapidly developing thunderstorms. This type of tornado is most common along the front ranges of the Rocky Mountains, the Plains, and the Western States.
• Tornadoes may appear nearly transparent until dust and debris are picked up.
• Occasionally two or more tornadoes may occur at the same time.
• Waterspouts are weak tornadoes that form over warm water.
• Waterspouts are most common along the Gulf Coast and southeastern states. In the western United States, they occur with cold late fall or late winter storms, during a time when you least expect tornado development.
• Waterspouts occasionally move inland becoming tornadoes causing damage and injuries.
   

How Do Tornadoes Form?
 

1. 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.
2. Rushing air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.
3. 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.
4. A lower cloud base identifies an area of rotation known as a rotating wall cloud. This area is often nearly rain-free.
5. Moments later a strong tornado develop in this area. Softball-size hail and damaging "straight-line" winds also occur within this storm.

Tornadoes Take Many Shapes and Sizes

Weak Tornadoes
 

• 69% of all tornadoes
• Less than 5% of tornado deaths
• Lifetime 1-10+ minutes
• Winds less than 100 mph

  Strong Tornadoes

• 29% of all tornadoesMay last 20 minutes or longer
• Winds 110-205 mph

  Violent Tornadoes

• Only 2% of all tornadoes
• 70% of all tornado deaths
• Lifetime can exceed 1 hour
• Winds greater than 205 mph

Tornado Myths

Myth: Areas near rivers, lakes, and mountains are safe from tornadoes.
 

FACT: No place is safe from tornadoes. In the late 1980's, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000 ft. mountain.

MYTH: The low pressure with a tornado causes buildings to "explode" as the tornado asses overhead.
FACT: Violent winds and debris slamming into buildings cause most structural damage.

MYTH: Windows should be opened before a tornado approaches to equalize pressure and minimize damage.
FACT: Opening windows allows damaging winds to enter the structure. Leave the windows alone: instead, immediately go to a safe place.

Occurrence of Tornadoes In Texas:

• A secondary tornado maximum occurs in the fall.
• Tornadoes are most likely to occur between 3 and 9 p.m., but have been known to occur at all hours of the day or night.
• The average tornado moves from southwest to northeast, but tornadoes have been known to move in any direction. The average forward speed is 30 mph but may vary from nearly stationary to 70mhp

Who's Most At Risk?
 

• 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 order to get more info, please contact the local Red Cross, and ask for the brochure entitled "Tornadoes... Nature's Most Violent Storms".

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