I hope to explain to you about tornadoes.
Tornadoes are local storms of high-speed, rotating winds (Brown & Brown 219). They are strong windstorms that occur mostly in the central and southern U.S. during
the spring and early summer. Tornadoes are formed when warmer, lighter air from the
south gets trapped below heavier, colder air from the north. When this happens, warm
air rushes upward and begins to spin. Winds may reach two hundred to five hundred
miles per hour (Long 15).
Tornadoes are small, intense storms. Six hundred to seven hundred are
reported each year in the U.S. In some regions, tornadoes are called "twisters" or
"cyclones." Damage paths are a few hundred feet wide and a few miles long.
One out of every four tornadoes occur between four and six P.M. Tornado comes from
the Spanish word tronado, or thunderstorm. Texas holds the record for having the
greatest number of tornadoes. They can develop over large areas and can be
detected with weather radar (Armbuster and Taylor 11-12).
Tornadoes begin where two kinds of air masses meet. When warm, moist air
meets a cold front, a tornado is possible (Brown and Brown 206). In a tornado, first
comes a strong thunderstorm. During a strong one, there are constant updrafts (Armbuster and Taylor 22-23). The cumulus clouds and the updraft begin to grow stronger. This draws in more warm air, turning cumulus clouds into cumulonimbus clouds. The tops of the clouds reach the cold stratosphere, so the ascending air becomes cold. The chilling creates strong downdrafts that bring rain and create a squall line, or line of hurricanes. Slowly spinning, the vortex, or air that forms a whirlpool, forms within the cloud. Both the updrafts and downdrafts begin to grow stronger. The spiral grows tighter and spins faster, producing a whirlpool shaped updraft (Smith 50-51). The tornado is then spawned from the cumulonimbus base (Armbuster and Taylor 22). The spinning funnel cloud begins to stretch downward. As the tornado becomes more intense, the funnel cloud grows larger. The funnel touches down with explosive force (Smith 50-51).
Two conditions cause the vortex to spin faster. The pressure in the vortex drops. This causes an inward pulling force. An outward pull is generated by the vortex's rotation. These conditions cause the sides of the vortex to be sealed off. No air is able to be sucked up from the sides. Because of this, the updraft becomes stronger. The speed of wind decreases the vortex's diameter. The column of air is narrowed and stretches downward.
The newly formed vortex can spin much faster than the larger vortex and reaches very close to the ground. The greatest wind speeds in the vortex are at the base of the spiral. It is now called a funnel cloud (Armbuster and Taylor 27).
Tornado alley is the place in which there is frequent tornado activity. The
boundary runs from Texas, northward through Oklahoma and Iowa (Brown and
Brown 189). Tornado alley consists of Montana, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, New Mexico, Colorado, and Wyoming (Lampton 15-16). Tornadoes can strike anywhere, but they usually hit where there's lots of flat land
Tornadoes can occur in any one of the fifty states, but they cause the most
damage in Texas, Oklahoma, Kansas, and Missouri. Although tornadoes are most
destructive in Australia and the U.S., they can occur in almost any part of the world
(Brown and Brown 203 and 206).
There are some tornadoes that caused massive destruction in the past. The tri-
state tornado of March 18, 1925 was one of them. This tornado started in Alaska. Then,
it came toward Texas and mixed with warm, wet air, which pushed the tornado
northeast. The tornado then moved from Oklahoma through Arkansas. It was 3/4 of a
mile wide and it moved sixty miles per hour (Brown and Brown 154-158).
Another tornado was the tornado of 1931. It lifted a train off the tracks. The train
and passengers were carried through the air and dropped eighty feet from the tracks.
One hundred seventy passengers were aboard. Many people were hurt, but only one
person was killed.
The last tornado is the tornado of 1974. In 1974, a series of tornadoes hit
Missouri, Indiana, Illinois, and ten other states. It killed three hundred fifteen people in
twenty-four hours (Branley 20-21).
Waterspouts are tornadoes that occur over oceans or lakes. They form when a
center of low air pressure develops, causing wind to whirl. A thick, black rotating cloud
forms, with a rotating column of air going beneath the cloud, to the water's surface. The
atmosphere condenses in the column and surface water is drawn up at the column's
base. The air column is now visible. Most waterspouts measure twenty to two-hundred
feet in diameter. They usually occur in the tropics (Wendland 147). A waterspout's
lifetime is very short, but often destructive (Brown and Brown 205). Winds in a
waterspout move slower than the winds in regular tornadoes. Waterspouts are also
less deadly than land storms (Lampton 31). Dust devils are funnels of hot air that whirl up from the desert and other dry, dusty places (Harvey 15).
I have explained to you about tornadoes. I think that tornadoes are very destructive, yet they are great natural forces of nature. The more we learn about them, the more we can prevent them from killing and injuring us.
1. Armbuster, Ann, Taylor, Elizabeth A. Tornadoes. New York: Franklin Watts, 1989.
2. Branley, Franklyn M. Tornado Alert. U.S.A.: Harper Collins Publishers, 1989.
3. Brown, Billy Walker, Brown, Walter R. Hurricanes and Tornadoes. U.S.A.: Addison-Wesley Publishing Co., 1972.
4. Harvey Doug. "tornadoes." Weather, Kid's Discovery l994: l5
5. Lampton,Christopher. Tornado. Brookfield, Connecticut: Millbrook Press, l991.
6. Long, Jack. Why is the Sky Blue? New York City, New York: Gallery Books, 1989.
7. Smith, Robert H. Weather and Climate. Virginia: Time-life, 1992>
8. Wendland, Wayne M. "Tornado" and "Waterspout." The World Book Encyclopedia 1995