Tornadoes
Tornadoes are one of weathers most
deadly and fascinating forces. Even though they are often limited by size (not being more
than one kilometer wide at most) they leave vast areas of destruction and death behind
them. They are also called twisters or cyclones.
Tornadoes are characterized by violent winds that swirl in a counter
clockwise direction north of the equator and clockwise south of the equator. Most people
recognize them as a towering black funnel extending downward from the base of a large
cumulonimbus cloud. It rotates at speeds up to three hundred miles per hour (480 kpm) or
in some rare cases, even faster. In the center of the tornado, the air pressure is very
low in comparison to surrounding air pressure.
The speed of the wind is the primary cause of deaths and destruction of
property. Many people are killed by flying objects and debris (missiles). The funnel
shaped cloud travels in a skip like movement, and usually never lasts for more than a
couple of minutes in any one given place. It is because of this skip movement that the
tornado leaves some areas wrecked while others a few yards away almost untouched.
Certain parts of the world (ie. Australia, the Midwestern and Southern
US) are more prone to have tornadoes. They also occur more frequently in the spring and
summer months. Tornadoes usually occur as part of a severe thunderstorm and often come in
advance of cold fronts, however, they can also occur (although less frequently) ahead of
warm fronts, and even behind cold fronts.
The greatest killer tornado in the United States occurred during the
year 1925 in Indiana, Illinois, and Missouri. It was the fastest and largest one ever
recorded, with a destructive path two hundred and twenty miles long and one mile wide, and
traveled at a speed of sixty miles per hour. It killed six hundred ninety five people and
injured over two thousand.