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Auburn, Feb. 21---Each year many people are hurt or killed by tornadoes and severe thunderstorms in Alabama despite advance warnings. Some did not hear the warning, while others heard the warning but did not heed it.

Once you receive a warning or observe threatening skies, you must make the decision to seek shelter before the storm arrives. It could be the most important decision you will ever make.

Tornadoes occur in many parts of the world and in each of the 50 U.S. states. However, no area is more favorable to their formation than the continental plains and Gulf Coast of the U.S. during April, May and June. Tornadoes are least frequent in the United States during the winter months. However, Alabamians know first hand that damaging tornadoes can develop at any time of year. Several deadly tornadoes swept across the state this past fall and, just last week, high winds from severe thunderstorms caused a death and much damage.

Tornadoes travel at an average speed of 30 miles per hour, but speeds ranging from stationary to 70 miles per hour have been reported, says Dr. Tony Cook, Extension program specialist with the Alabama Cooperative Extension System. Most tornadoes move from the southwest to the northeast, but their direction of travel can be erratic and change suddenly.

In populated areas, it is very dangerous to attempt to flee to safety in an automobile. While chances of avoiding a tornado by driving away in a vehicle may be better in open country, it is

still best in most cases to seek or remain in a sturdy shelter such as a house or building. Even a ditch or ravine offers better protection than a vehicle if more substantial shelter is not available.

While hail may or may not precede a tornado, the portion of a thunderstorm with accompanying hail is often the area where strong violent tornadoes are most likely to occur.

Once large hail begins to fall, it is best to assume that a tornado may be nearby and seek appropriate shelter. Once the hail has stopped, remain in a protected area until the

thunderstorm has moved away. This will usually be 15 to 30 minutes after the hail stops.

The tornado's atmospheric pressure drop plays, at most, a minor role in the damage process, Cook says. Most structures have sufficient venting to allow for the sudden drop in atmospheric pressure.

"Opening a window, once thought to be a way to minimize damage by allowing inside and outside pressures to equalize, is not recommended." In fact, if a tornado gets close enough to a structure for the pressure drop to be experienced, the strong tornado winds probably already will have caused the most damage. Furthermore, opening the wrong window can actually increase damage.

While most tornado damage is caused by violent winds, most tornado injuries and deaths result from flying debris. Cook says small rooms, such as closets or bathrooms, in the center of a home or building offer the greatest protection from flying debris. Such rooms are also less likely to experience roof collapse. Always stay away from windows and exterior doors.

Tornado winds may produce a loud roar similar to that of a train or airplane. At night or during heavy rain, the only clue to a tornado's presence may be its roar.

Thunderstorms can also produce violent straight-line winds which produce a similar sound. If any unusual roar is heard during threatening weather, take cover immediately.

Although most tornadoes occur during the mid-afternoon or early evening ( 3 p.m. - 7 p.m.), they can occur at any time -- often with little or no warning.

The key to survival is advanced planning. Have a tornado emergency plan at work and school and conduct drills. All members of a household should know where the safest areas of their home are. Identify interior bathrooms, closets, halls or basement shelter areas. Be sure every family member knows that they should move to such safe areas at the first signs of danger. There may be only seconds to act.

SOURCE: DR. TONY COOK (jacook@aces.edu), Extension Program Specialist, Alabama Cooperative Extension System, (334) 844-2233