2. Wind Speeds
4. Number Of Tornadoes Per Year
5. Deaths And Injuries
B. Types Of Tornadoes
C. Average Tornado
2. Distance Moved
D. Frequency Of Tornadoes
1. Southern States
2. Northern States
III. Where And When Tornadoes Occur
A. North America
1. Rocky Mountains
2. Appalachian Mountains
B. Other Areas Of The World
C. Spring And Summer
V. Detection Of Tornadoes
A. Doppler Radar
A. Atmospheric Conditions
B. Environmental Clues
VII. Staying Safe
A. Safety Rules To Follow
B. Where To Go
1. Storm Shelter
C. What To Avoid
Facts. A tornado is defined as a violently rotating column extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of two hundred and fifty miles per hour or more. Damage paths can be in excess of one mile wide and fifty miles long. In an average year, eight hundred tornadoes are reported nationwide, resulting in eighty deaths and over one thousand five hundred injuries.
Types Of Tornadoes. The average tornado is usually split up into categories based on the strength of the tornado. Most tornadoes, about sixty nine percent (69%), are considered weak, which means they usually last between one minute and ten minutes, have winds less that one hundred and ten miles per hour, and the percent of deaths that occur during these is less than five percent. Strong tornadoes, about twenty nine percent (29%), may last about twenty minutes, have winds between one hundred and ten and two hundred and five miles per hour, and the percent of deaths that are found are about thirty percent of all tornado deaths. The last category for tornadoes is violent ones. With these comes winds greater than two hundred and five miles per hour, they can last about an hour, and have seventy percent of all deaths from tornadoes.
Variations. Some variations of tornadoes are that they can be found in the early stages of rapidly developing thunderstorms. This type of tornado is most common along the range 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.
Another type of tornado is known as a waterspout. This is a weak tornado that forms over warm water. They 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 it to develop. They occasionally move inland becoming tornadoes that can cause a great deal of damage and many injuries.
Average Tornado. The average tornado moves from southwest to northeast, but they have been known to move in any direction. The average forward speed is about thirty miles per hour but can vary from that to seventy before it really gets going.
Frequency Of Tornadoes. Tornadoes can occur at any time of the year. In the southeastern states, peak tornado occurrence is March through May, while peak months in the northern states are during the summer months. They are most likely to occur between three and nine o’clock p.m. but have been known to occur at all hours of the day or at night.
Where Tornadoes Come From:
Energy. Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm’s energy sometimes gets focused into something as small as a tornado.
Where And When Tornadoes Occur:
North America. Whenever and wherever conditions are right, tornadoes are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains.
Spring And Summer. They occur mostly during the spring and summer, however, the tornado season comes early in the south and later in the north because spring comes later in the year as one moves northward. They usually occur during the late afternoon and early evening. However, they have been know to occur in every state in the United States, on any day of the year, and at any hour.
Wind. The damage from tornadoes comes from the strong winds they contain. It is generally believed that tornadic wind speeds can be as high as three hundred miles per hour in most violent tornadoes. Wind speeds that high can cause automobiles to become airborne, rip ordinary homes to shreds, and turn broken glass and other debris into lethal missiles.
The biggest threat to living creatures, including humans, from tornadoes is from flying debris and from being tossed about in the wind. It used to be believed that the low pressure in a tornado contributed to the damage by making buildings “explode” but this is no longer believed to be true.
Detection Of Tornadoes:
Doppler Radar. Today, the development of Doppler radar has made it possible, under certain circumstances, to detect a tornado’s winds with a radar. However, human beings remain an important part of the system to detect tornadoes because not all of them occur in situations where radar can “see” them.
Ordinary citizen volunteers make up what is called SKYWARN (www.skywarn.org) network of storm spotters who work with their local communities to watch out for approaching tornadoes, so that those communities can take appropriate action in the event of a tornado. Spotter information is relayed to the National Weather Service, which operates the Doppler radars and which issues warnings, usually relayed to the public by radio and televison, for communities ahead of the storms using all the information they can obtain from weather maps, modern weather radars, storm spotters, monitoring power line breaks, and so on.
Atmospheric Conditions. Tornadoes can be predicted, but only to a limited extent. Although the process by which tornadoes form is not completely understood, scientific research has revealed that tornadoes usually form under certain types of atmospheric conditions. Those conditions can be predicted, but not perfectly.
When forecasters see those conditions, they can predict that tornadoes are likely to occur. However, it is not yet possible to predict in advance exactly when and where they will develop, how strong they will be, or precisely what path they will follow.
There are some “surprises” every year, when tornadoes form in situations that do not look like the right conditions in advance, but these are becoming less frequent. Once a tornado is formed and has been detected, warnings can be issued based on the path of the storm producing the tornado, but even these cannot be precise about who will or will not be struck.
Environmental Clues. Some clues to look for in the environment that could give you an idea that a tornado is coming are that the sky gets dark and sometimes green, there are walls of clouds everywhere, even close to the ground, large hail comes down, and loud roars, like a freight train. These are all things that help us to determine if we may experience a tornado.
Safety Rules To Follow. During a tornado, you should always take the proper safety rules so that you can stay safe with your family. The main rule to follow is be protected from flying and falling debris. If you hear a tornado warning, seek shelter immediately!! The storm is known to come at any given moment.
Where To Go. During a tornado, you must seek shelter as soon as possible. A storm shelter is the best choice, if you have one. If you have a basement, go there and get under something sturdy to shelter you from falling debris.
If you have no storm shelter or basement, go to an interior room without windows on the first floor of your home. Bathrooms are a good choice because the plumbing reinforces the walls. Closets are also a good choice because they normally have no windows. The idea is to put as many walls between you and an approaching tornado as possible. Flying debris can penetrate through exterior walls easily.
What To Avoid. Some things to avoid during a tornado are definitely windows. It used to be thought that opening windows would reduce a tornado’s damage to a home, but this is no longer considered to be good advice. Leave windows alone completely and get to a safe place immediately.
If you are in an automobile, don’t drive away from the storm. Seek shelter immediately to avoid having the car being lifted into the funnel. One of the most dangerous places during a tornado is in an automobile so get out as soon as possible!
Rosenfeld, Jeffrey O.; Eye of the Storm: Inside the World’s Deadliest Hurricanes, Tornadoes, and Blizzards; Harpercollins Trade Sales Dept, January 1999
Compton’s Encyclopedia Online; www.comptons.com
SKYWARN Online; www.skywarn.org