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Tornadoes: Introduction
The eerie sight of a funnel groping downward from a dark sky and the
deafening sound of violently rotating winds help to make the tornado
one of nature's most feared hazards. Tornadoes are highly publicized
for the destruction and loss of life that they can leave in their
path. While Kentucky does not lie in the heart of Tornado Alley, the
state averages nearly ten tornadoes per year.
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Photo Credit: NOAA Photo
Library, NOAA Central
Library; OAR/ERL/National
Severe Storms Labratory
(NSSL). |
Tornadoes can be spawned by thunderstorms during any time of year in
Kentucky. Fortunately, less than one percent of all thunderstorms
produce tornadoes. The storms that are most likely to produce
tornadoes are thunderstorm supercells. These powerful storms are most
common during spring when tropical and polar air masses clash over the
Southeast and Midwest. They develop at the leading edge of a cold
front or along a squall line ahead of the front. Sharp temperature
contrasts between the leading warm air and trailing cold air are one
indicator of the potential for severe thunderstorms and tornadoes.
History shows that tornadoes can be unpredictable, but certain
tendencies are noted. Most tornadoes develop in the afternoon or
early evening hours. They most frequently move along the ground from
the southwest toward the northeast at speeds near 30 miles per hour,
but as high as 70 miles per hour. Most tornadoes are classified as
weak tornadoes, have lifetimes of only a few minutes, and reach wind
speeds near 100 miles per hour. Violent tornadoes are rare, but their
impacts are often devastating. They are responsible for well over
half of all tornado-related deaths. A single tornado with wind speeds
reaching 300 miles per hour can stay on the ground for more than an
hour and cut a swath of damage more than one mile wide. On rare
occasions, atmospheric conditions lead to an outbreak of tornadoes,
such as occurred on April 3, 1974.
The sudden and massive destruction that can be caused by tornadoes
highlights the importance of mitigation. Fortunately, advances in
early warning capabilities have greatly reduced the number of
casualties caused by tornadoes. The effectiveness of early warning
systems emphasizes the need for communities to be prepared in advance
by implementing strategies to minimize the damage and disruptions
created when a tornado strikes.
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