Facts About Tornadoes
Q. What is a tornado? A. 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. In an average year, 800 tornadoes are reported nationwide.
Q. How do tornadoes form? A. 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. Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical. 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.
Q. Are there different kinds of tornadoes? A. Some tornadoes may form during the early stages of rapidly developing thunderstorms. This type or tornado is most common along the front range of the Rocky Mountains, the Plains, and the Western State. 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.
Q. What should people look for to identify likely conditions for tornadoes? A. Dark, often greenish sky; large hail; wall cloud; a loud roar, similar to a freight train. Some tornadoes appear as a visible funnel extending only partially to the ground. Look for signs of debris below the visible funnel. Some tornadoes are clearly visible while others are obscured by rain or nearby low-hanging clouds.
Q. When are tornadoes most likely to occur? A. Tornadoes can happen any time of the year and any time of day. In the southern states, peak tornado season is from March through May. Peak times for tornadoes in the northern states are during the summer. A few southern states have a second peak time for tornado outbreaks in the fall. Tornadoes are most likely to occur between 3 p.m. and 9 p.m. Q. Who is most at risk during tornadoes? A. People in automobiles and people in mobile homes; people who may not understand a warning due to a language barrier; the elderly and very young; people with physical or mental impairments.
Q. What dangers other than tornadoes often accompany thunderstorms? A. Flash floods, lightning, damaging straight-line winds, and large hail.
Prepare: Q. I live in an area where there are a lot of tornadoes -- what can I do to be prepared ahead of time? A. The most important steps you can take to protect yourself and your family is to stay tuned to weather forecasts for the most current information, watches and warnings. Have a NOAA Weather Radio with a warning alarm tone and a battery back-up. These special radios can be set up to turn on automatically and alert you when a tornado watch or warning is issued, even when you are sleeping. Listen to radio and television for more information. You should also develop a plan for you and your family so you know where to take shelter at home, at work, at school or when outdoors.
Q. What actions should people take to protect themselves during a tornado? A. Move to a pre-designated shelter such as a basement in a home or building. If an underground shelter is not available, move to an interior room or hallway on the lowest floor and get under a sturdy piece of furniture. Stay away from windows; get out of cars -- do not try to outrace a tornado. If you're caught outside, lie flat in a nearby ditch or depression.
Myths: Q. Should I open my windows before a tornado approaches? A. It's a myth that open windows equalize pressure and minimize damage when a tornado strikes. Opening windows allows damaging winds to enter the structure. Leave the windows alone and immediately go to a safe place.
Q. Doesn’t the low pressure associated with a tornado cause buildings to explode? A. Violent winds and flying debris slam into buildings and cause most structural damage .