[Causes of Wind] [Types of Winds] [Hail Storm] [Hurricane] [Tornado] [Typhoon] [Wind Erosion]Tornado
In any seasons of this world, be it summer, fall, winter, and spring,
tornadoes can occur. But they occur most in the spring because the
temperature contrast is greatest during that time of year. Also, the warm
surface air is more prevalent during the spring and summer months while
absent during the winter months. The most powerful tornadoes occur during
the month of April when horizontal and vertical temperature and moisture
contrasts are the greatest.
What is a Tornado?
A tornado is a violent windstorm characterized by a twisting,
funnel-shaped cloud. It is spawned by a thunderstorm (or sometimes as a
result of a hurricane) and produced when cool air overrides a layer of
warm air, forcing the warm air to rise rapidly. The damage from a tornado
is a result of the high wind velocity and wind-blown debris. Tornado
season is generally March through August, although tornadoes can occur at
any time of year. They tend to occur in the afternoons and evenings: over
80 percent of all tornadoes strike between noon and midnight.
Did you know?
Tornadoes can be nearly
invisible, marked only by swirling debris at the base of the funnel.
Some are composed almost entirely of windblown dust and still others are
composed of several mini-funnels.
On average, the United States
experiences 100,000 thunderstorms each year. Approximately 1,000
tornadoes develop from these storms.
Although tornadoes do occur
throughout the world, the United States experiences the most intense and
Tornadoes produce the most
violent winds on earth. Tornado winds can approach speeds as high as 300
miles per hour, travel distances over 100 miles and reach heights over
60,000 feet above ground.
In November 1988, 121
tornadoes struck 15 south central states, resulting in 14 lives lost and
damages reaching $108 million.
According to the National
Weather Service, about 42 people are killed because of tornadoes each
Fujita - Pearson Tornado Scale
40-72 mph, chimney damage, tree branches broken
73-112 mph, mobile homes pushed off foundation or overturned
113-157 mph, considerable damage, mobile homes demolished, trees
158-205 mph, roofs and walls torn down, trains overturned, cars thrown.
207-260 mph, well-constructed walls leveled.
261-318 mph, homes lifted off foundation and carried considerable
distances, autos thrown as far as 100 meters.
Tornado Danger Signs
An approaching cloud of
debris can mark the location of a tornado even if a funnel is not
Before a tornado hits, the
wind may die down and the air may become very still.
Tornadoes generally occur
near the trailing edge of a thunderstorm. It is not uncommon to see
clear, sunlit skies behind a tornado.