TORNADOES - Nature's Most Violent Storms!
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What Causes Tornadoes?
Thunderstorms develop in warm, moist air in
advance of usually eastward moving cold fronts. These thunderstorms often produce large hail, strong winds and tornadoes. Tornadoes in the winter and early spring are often
associated with strong, frontal systems that form in the Central States and move east. A tornado is defined as a violently
rotating column of air extending from a thunderstorm to the ground. The most violent are capable of tremendous destruction
with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long. |
What Are Tornadoes?:
A tornado is a violently rotating column of air in contact with the ground.
The air column may be seen when it contains condensation in the form of a cloud or surface dust and
debris. Often its appearance is a result of both. When a tornado touches the ground there usually
is a swirl of dust and debris even when the visible cloud portion is missing or fails to reach all
the way to the ground. When the column of air is aloft and does not produce damage, the visible
portion is properly called a funnel cloud. A waterspout is a tornado in contact with a water surface.
Size: Tornadoes vary greatly in size, intensity and appearance. Sixty-two percent of tornados fall
into the weak category with wind speeds 100 MPH or less accounting for less than 3% of deaths from tornadoes.
About 1 in every 3 are classified as strong when wind speeds reach 200 MPH with an average path length of 9
miles and width of 200 yards. About 30% of all deaths occur from this type. Nearly 70% of all fatalities
result from violent tornadoes (2%) these can last for hours. Average path lengths are 26 miles and 425 yards
with the largest exceeding a mile in width and winds approaching 300 MPH.
Color: The color of a tornado is determined by a number of factors such as the amount and direction of sunlight,
type of debris being picked up at the surface.
Shape: The shape may vary widely and usually does during its life. In early stages it may become highly tilted and
shrink in size. With exceptionally large tornadoes the classic funnel shape may be absent appearing to be a large
turbulent cloud near the ground. It may even be mistaken for a large rain shaft or even a non-weather event such
as a fire.
Series: Sometimes a series of two or more tornadoes may be associated with a parent thunderstorm. Occasionally
two or more can occur simultaneously extending downward from he same thunderstorm. As the parent thunderstorm
moves along tornadoes may form, travel along in contact with the ground, and dissipate or lift, followed shortly
by other touchdowns. Tornadoes can also be made up of a number of smaller but intense vortices rotating about a
common center. The most intense damage is concentrated along the paths of the small vortices.
How They Develop: Except for weak tornadoes and waterspouts in coastal areas, they usually develop from strong or
severe thunderstorms. Most significant tornadoes have their origin within the right rear quadrant of the thunderstorm
where a circulation develops at heights between 15,000 and 30,000 ft. A tornado or funnel cloud may be observed
further downward toward the ground surface. Tornado development can also occur along the leading edge of a single
thunderstorm or line of thunderstorms. While dangerous, such tornadoes are usually weak and short-lived. Tornadoes
occasionally accompany tropical storms and hurricanes that move over land and are most common to the right and ahead
of the path of the storm center as it comes onshore. Before thunderstorms develop a change in wind direction and an increase in wind speed with increasing height creates
an invisible spinning effect in the lower atmosphere. Rising air within the thunderstorm updraft tilts the rotating
air from horizontal to vertical. |
Myth
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Myths and Facts about Tornadoes
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Myth 1
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The low pressure with a tornado causes buildings to explode as the tornado passes overhead.
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Fact 1
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Violent winds and debris slamming into buildings cause most damage.
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Myth 2
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Areas near rivers, lakes, and mountains are safe.
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Fact 2
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NO PLACE IS SAFE!
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Myth 3
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Windows should be opened before a tornado approaches to equalize pressure.
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Fact 3
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Opening windows allows damaging winds to enter. Leave windows alone and seek safety
immediately.
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Occurrences: Tornadoes can occur at anytime of the year. 1) In the Southern states peak tornado occurrence is
in March through May. 2) In the Northern states peak months are in the Summer. In some states a secondary occurrence
may occur in the Fall. 3) Tornadoes have been most likely to occur between 3 and 9 p.m. but have been known to occur at any time.
4) The average tornado moves from southwest to northeast, but can move in any direction. The average forward speed is 30MPH but
may vary up to 70MPH (or higher). 5) Total number of tornadoes is probably higher than indicated in the Western states. Sparse population
reduces the number reported.
What To Look For: Dark greenish sky, wall cloud, large hail, loud roar similar to a freight train. Some tornado’s appear as a
visible funnel extending only partially to the ground. Look for signs of debris being kicked-up below the visible funnel. Some tornadoes are
clearly visible while others are obscured by rain or nearby low-hanging clouds.
These Dangers Often Accompany Thunderstorms: Flash floods which are the number 1 weather killer; lightning which
kill 75 - 100 people per year; damaging straight-line winds can reach 140 MPH (or higher); and large hail which can reach the size of a grapefruit.
What You Can Do
Before The Storm:
1) Develop a plan for you and your family for home, work, school and when outdoors.
2) Have frequent drills.
3) Know the area in which you live and keep a highway map nearby to follow storm movement from weather bulletins.
4) Have a
NOAA weather radio with a warning alarm tone and battery back-up to receive warnings.
5) Listen to radio and television for
warnings.
6) If planning a trip outdoors listen to the latest forecasts and take necessary action if threatening weather is
possible.
If A Warning is Issued (or threatening weather approaches): 1) In a home or building move to a pre-designated shelter such
as a basement. 2) If an underground shelter is not available move to an interior room or hallway on the lowest floor and get
under a sturdy piece of furniture. 3) Stay away from windows. 4) Get out of automobiles. 5) Do not try to outrun a tornado
in your car, instead leave it immediately. 6) If caught outside or in a vehicle, lie flat in a nearby ditch or depression.
7) Mobile homes even if tied down offer little protection and should be abandoned and 8) If hail starts and appears large drive under the closest
bridge or into a nearby building. Getting hit with hail as large as grapefruit is no fun and can be very damaging to body and vehicle (except perhaps a tank)!
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Prepare a Disaster Kit This should include as a minimum: A 3-day supply of water (1 gal. per person per day), one change of
clothing and footwear per person, one blanket or sleeping bag per person, a first-aid kit including medicines, emergency tools
including a battery powered NOAA Weather Radio, a portable radio, flashlight and plenty of extra batteries, an extra set of car
keys and credit card or cash, and special items for infants, elderly or disabled family members, and don’t forget food for each
person. You can get these and the book (cover shown at left) including all the survival food and preparedness items you'll need right here in Karinya.
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Go to this reference for food and other
supplies needed for SURVIVAL situations. |
Sources: National Oceanic and Atmospheric Administration (NOAA)
U.S. Dept. of Commerce, National Weather Service,
Federal Emergency Management Agency, American Red Cross
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