The occurrence of tornadoes
are most frequent in the United States east of the Rocky Mountains
during the spring and summer, In an average year, 800 tornadoes
are reported resulting in 1,500 injuries and 80 deaths.
What conditions lead to tornadoes?
Tornadoes are often produced in early spring during thunderstorms
associated with strong frontal systems that form in the Central
States and move east. Thunderstorms in the central plains frequently
develop along a "dry line" which separates very warm,
moist air to the east from hot, dry air to the west. Tornado-producing
thunderstorms may form as the dry line moves east during the afternoon
hours. A change in wind direction and an increase in wind speed
with increasing height creates an invisible, horizontal spinning
effect in the lower atmosphere.
Rising air within the thunderstorm updraft tilts the
rotating air from horizontal to vertical. Most strong and violent
tornadoes form within this area of rotation. The lower cloud base
in the rear of a storm identifies an area of rotation known as a
rotating wall cloud. This area is often nearly rain-free.
SEVERE WEATHER DEFINITIONS
Tornado Watch
Conditions are favorable for tornadoes (or severe thunderstorms)
to occur. Stay informed.
Tornado Warning
A tornado or severe thunderstorm is occurring or is imminent.
Seek shelter immediately!
Severe Thunderstorm
A storm that produces wind damage, dime-size hail or larger and
winds up to 58 mph.
Tornado
A violently rotating column of air in contact with the ground
and coming from a thunderstorm.
Funnel cloud
Similar to a tornado, but not in contact with the ground.
WHAT TO DO WHEN A TORNADO
THREATENS
If your area is threatened by a tornado, the thought that should
be uppermost in your mind is how to save lives, not possessions.
Time is of the essence. You may only have time to duck under a sturdy
table or get into an interior hallway.
DURING A TORNADO
Absolutely avoid buildings with large free-span roofs such as auditoriums
and gymnasiums, as well as upper stories of multi-story buildings.
Stay away from west and south walls and windows. Remember, lowest
level, smallest room, center part.
Seek safe places for shelter, such as modern, steel-reinforced
office buildings, storm shelters, tunnels, caves, root cellars,
sub-basements, bank vaults, underground parking facilities, basements,
interior corridors, and subways. Keep away from mobile homes and
parked cars.
HOMES OR SMALL BUILDINGS
Go to the basement (if available) or to an interior room on the
lowest floor, such as a closet or bathroom. Upper floors are unsafe.
If there is no time to descend, go to a closet, a small room with
strong walls, or an inside hallway. Wrap yourself in overcoats or
blankets to protect yourself from flying debris.
CARS OR MOBILE HOMES: ABANDON
THEM IMMEDIATELY!
Most deaths occur in cars and mobile homes. If you are in either
of those locations, leave them and go to a substantial structure
or designated tornado shelter. An automobile, whether parked or
moving is the most dangerous place to be. Violent winds can tumble
a car over and over, crushing it and its occupants. Seek shelter
immediately in the kinds of structures mentioned in this article.
Do not attempt to drive out of the storm path, because this has
proven fatal to many motorists. If you are trapped in open country,
seeking shelter in a ravine or ditch may be your only hope. However
be aware of the torrential rains that often accompany tornadic weather.
OFFICE BUILDINGS, DORMATORYS
OR
HIGH RISE BUILDINGS
If you are in an office building, dormitory, or any other multi-story
structure, go to interior hallways on a lower floor, preferably
in the basement. In homes, a basement usually offers the greatest
safety. If no basement is available, take cover under heavy furniture
in the center of the house against strong inside walls. Covering
yourself with a rug or blanket provides some protection against
flying glass and falling debris. If you are in a mobile home park,
or any non- reinforced structure without a basement, seek shelter
elsewhere, such as a public building, friend's basement, community
shelter, etc.
SCHOOLS, HOSPITALS, FACTORIES,
OR SHOPPING CENTERS
Go to interior rooms and halls on the lowest floor. Stay away from
glass enclosed places or areas with wide-span roofs such as auditoriums
and warehouses. Crouch down and cover your head. Don't take shelter
in halls that open to the south or the west. Centrally-located stairwells
are good shelter. Also, avoid school buses unless they are part
of an evacuation plan. At shopping centers, stay away from large
glass windows. If possible, take cover under a strong counter.
IF NO SUITABLE STRUCTURE
IS NEARBY
Lie flat in the nearest ditch or depression and use your hands to
cover your head. Be alert for flash floods.
No matter where you are, do some advance planning
if possible. Identify protective areas you can get to in a hurry.
Obtain a "Secure-Weather Alert" radio that will provide
an alarm if a tornado watch is in affect in your county. Call the
National Weather Service only to report a tornado you have actually
sighted.
TO PREPARE FOR A TORNADO
Store water in clean covered containers. You should keep disaster
supplies in your home at all times (i.e. flashlight, candles, matches,
battery powered radio, cell phone, etc.).
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