The definition of tornado is a twirling, narrow funnel of wind with speeds of 100 to 300 miles per hour that can damage anything in its path.
How a Tornado Forms
- Before a thunderstorm forms, there is an area in the lower atmosphere of horizontal, spinning air caused by a change in wind direction and an increase in the wind’s speed along with an increase in height.
- When warm air rises, the atmosphere is considered unstable. When the air is cooler than the surrounding air, it will sink and the atmosphere is said to be stable.
- When the thunderstorm starts to develop, the updraft lifts the area of spinning air, changing its pitch from horizontal to vertical. At this point, there is a large area of rotation, from two to six miles in diameter, where the tornado typically forms.
- A wall cloud will form, a low mass of clouds which rotates.
- A tornado forms, which is accompanied by high winds and damaging hail. Tornadoes are frequently spawned by huge thunderstorms called "supercells."
- Tornadoes will typically travel in a northeast direction, depending on the winds.
- Most tornadoes will not last for more than 10 minutes.
- A tornado's path can range from just 100 yards, to one mile wide, or to a path of up to 15 miles wide.
- "Tornado Alley" indicates the states which have the highest possibilities of having a tornado: Missouri, Indiana, Illinois, Arkansas, Oklahoma, Nebraska, Kansas, Colorado, and Texas. In these areas the plains are mostly flat and are where cold air masses from Canada and the Rocky Mountains collide with warm and moist air masses from the Gulf of Mexico.
- Tornadoes can form in any area at any time of the year; but, most tornadoes form in the southern regions of the U. S. in early spring. The tornado season every year goes from April until mid-June.
A tornado watch means that conditions are favorable for the formation of a tornado. It implies a severe thunderstorm warning, as any thunderstorm capable of producing a tornado will be severe. Usually, there will also be a threat for large hail and high winds.
- When a watch is issued, stay alert to changing weather conditions, especially looking for dark green clouds or orange-gray skies, hail, rotating clouds or funnels, and listen for a loud roar. Also, stay tuned to local weather updates and be ready to take action quickly.
A tornado warning means that either storm spotters have seen a funnel, or radar is indicating a possible funnel. Tornado sirens may sound in your area. You will need to take shelter immediately, listen for updates and remain in a safe place until the tornado has passed.
- If you are outside, go to a low-lying area, like a ravine or ditch and cover your head with your hands. Do not take shelter under an overpass. If you are in a trailer or car, seek shelter in a sturdy building immediately. If you are in a building, go to the basement or lowest floor and go to the center of an interior room, like a closet, bathroom, or hallway that is away from windows, doors, corners, and outside walls.
- F-0 (40-72 mph) Light damage characterized by broken tree branches, damaged chimneys, toppled shallow-rooted trees.
- F-1 (73-112 mph) Moderate damage characterized by peeled off roof surfaces, snapped tree trunks, overturned mobile homes, destroyed garages.
- F-2 (113-157 mph) Considerable damage characterized by damaged roof structures, destroyed mobile homes, airborne debris, uprooted large trees.
- F-3 (158-205 mph) Severe damage characterized by torn walls and roof structures, destroyed small buildings, most trees uprooted.
- F-4 (207-260 mph) Devastating damage characterized by destroyed well-constructed homes, structures lifted from their foundations, blown cars, airborne large debris.
- F-5 (261-318 mph) Incredible or violent damage characterized by lifted strong-framed houses from foundations, damaged concrete structures, airborne vehicle-size missiles and debarked trees.
An example of a tornado is the whirlwind that carried Dorothy and her dog Toto away to Oz in the movie The Wizard of Oz.