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Texas Tech University |
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Click on the links below to go to a particular topic.
Tornado Facts
Tornado Danger Signs
Tornado Watches and Warnings
Fujita Scale Damage Descriptions
How to Prepare
Safety Rules during a Tornado
After a Tornado
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Tornadoes are nature's most violent storms,
with wind speeds inside the most violent tornadoes exceeding 300 miles per hour.
This makes tornadoes very destructive and hence, very dangerous. The best way to
be able to protect yourself and others from this destructive force is to know
about it. This web page is designed with that purpose in mind. |
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Tornado Facts |
A tornado on the ground |
A tornado is a violently rotating column of
air extending from a thunderstorm to the ground.
Tornadoes are capable of destroying homes and vehicles and can cause fatalities.
Tornadoes may appear nearly transparent until dust and debris are picked up or a
cloud forms in the funnel. The average tornado moves SW to NE but they have been
known to move in any direction. The average forward speed is 30 mph but may vary
from stationary to 70 mph and have rotating winds in excess of 250 mph.
Tornadoes can accompany tropical storms and hurricanes as they move onto land.
Waterspouts are tornadoes that form over water.
Tornadoes can occur at any time of the year. They have occurred in every state,
but they are most frequent east of the Rocky Mountains during spring and summer
months. In the southern states, peak tornado occurrence is March through May,
while peak months in the northern states are during the late spring and early
summer. Tornadoes are most likely to occur between 3 and 9 p.m. but can happen
at any time. |
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Tornado Danger Signs |
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Look for:
A dark, often greenish sky,
Large hail,
A wall cloud, and/or,
A loud roar, similar to a freight train. |
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A wall cloud formation |
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Some tornadoes are clearly visible, while rain or nearby low-hanging clouds
obscure others. Before a tornado hits, the wind may die down and the air may
become very still. A cloud of debris can mark the location of a tornado even if
a funnel is not visible. Tornadoes generally occur near the trailing edge of a
thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado. |
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Tornado Watches and Warnings |
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The National Weather Service (NWS) issues a
tornado watch when tornadoes are possible in your area. Remain alert for
approaching storms. This is the time to remind family members where the safest
places within your home are located, and listen to the radio or television for
further developments. A tornado warning is issued by NWS when a tornado has been
sighted or indicated by weather radar. If a tornado warning is issued for your
area and the sky becomes threatening, move to your pre-designated place of
safety. Turn on a battery-operated radio and wait for further instructions.
Forecasters and researchers use a wind damage scale created by T. Theodore
Fujita to classify tornadoes and sometimes the damage done by other wind storms. |
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Fujita Scale Damage Descriptions |
The Fujita Scale uses numbers from 0 through
5 and the ratings are based on the amount and type of wind damage. The scale had
been calculated through F-12, which is Mach 1 - the speed of sound (750 mph) -
but tornado wind speeds are not expected to reach these speeds; see the F-6
description below.
F-0 Gale tornado (40-72 mph): Some damage to chimneys; breaks
branches off trees; pushes over shallow-rooted trees; damages sign boards.
F-1 Moderate tornado (73-112 mph): The lower limit is the
beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed
off foundations or overturned; moving autos pushed off the roads; attached
garages may be destroyed.
F-2 Significant tornado (113-157 mph): Considerable damage. Roofs
torn off frame houses; mobile homes demolished; boxcars pushed over; large trees
snapped or uprooted; light object missiles generated.
F-3 Severe tornado (158-206 mph): Roof and some walls torn off
well-constructed houses; trains overturned; most trees in forest uprooted.
F-4 Devastating tornado (207-260 mph): Well-constructed houses
leveled; structures with weak foundations blown off some distance; cars thrown
and large missiles generated.
F-5 Incredible tornado (261-318 mph): Strong frame houses lifted
off foundations and carried considerable distances to disintegrate; automobile
sized missiles fly through the air in excess of 100 meters; trees debarked;
steel-reinforced concrete structures badly damaged.
F-6 Inconceivable tornado (319-379 mph): These winds are very
unlikely. The small area of damage they might produce would probably no be
recognizable along with the mess produced by F-4 and F-5 wind that would
surround the F-6 winds. Missiles, such as cars and refrigerators would do
serious secondary damage that could not be directly identified as F-6 damage. If
this level is ever achieved, evidence for it might only be found in some manner
of ground swirl pattern, for it may never be identifiable through engineering
studies.
F-0 and F-1 tornadoes are considered "weak," F-2 and F-3 are "strong" and F-4
and F-5 are "violent." The National Weather Service accepted the Fujita Scale
for use in 1973 and Allen Pearson, then director of the National Severe Storms
Forecast Center, added the Pearson Scales for tornado path length and path
width, creating the Fujita-Pearson Scale. A separate page contains a table of
the complete Fujita-Pearson Scale. |
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How to Prepare |
 When a
tornado is coming, you have very little time to make life-or-death decisions.
Advance planning and quick response are the keys to surviving a tornado.
Develop
a plan for you and your family at home, work, school and when outdoors.
The
Federal Emergency Management Agency offers planning tips on its Internet site:
www.fema.gov/pte/displan.htm.
Identify
a safe place to take shelter.
Information
on how to build a “Safe Room” in your home or school is available from the
Federal Emergency Management Agency at
www.fema.gov/mit/saferoom.
Conduct
frequent tornado drills each tornado season.
Keep a
highway map nearby to follow storm movement from weather bulletins.
Have a
National Oceanographic and Atmospheric Administration (NOAA) Weather Radio with
a warning alarm tone and battery backup to receive watches and warnings.
NWS
watches and warnings are also available on the Internet. Go to the NWS Home Page
at www.nws.noaa.gov
for services or
weather.gov for weather and forecasts.
Listen
to radio and television for weather information.
Check
the weather forecast before leaving for extended periods outdoors. Watch for
signs of approaching storms.
If
severe weather threatens, check on people who are elderly, very young, or
physically or mentally disabled.
Practice
having everyone in your family go to your designated safe place in response to a
tornado threat.
Contact
your local emergency management office and NOAA for more information on
tornadoes.
Develop a communications plan
Pick
two places to meet: a spot outside your home for an emergency and a place away
from your neighborhood in case you cannot return home.
Choose
an out-of state friend as your “family check-in contact” for everyone to call if
the family gets separated.
Discuss
what you would do if advised to evacuate.
Prepare a Disaster Supply Kit
A 3-day
supply of water (one gallon per person per day) and food that won’t spoil.
One
change of clothing and footwear per person.
One
blanket or sleeping bag per person.
A first
aid kit including prescription medicines.
Emergency
tools, including a battery powered NOAA Weather Radio and portable radio,
flashlight, and extra batteries.
An
extra set of car keys and a credit card or cash.
Special
items for infant, elderly, or disabled family members.
Copies
of ID cards or driver’s licenses for all family members.
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Safety Rules during a Tornado |
Do not
get under an overpass or bridge. You are safer in a low, flat location.
In a
home or building, move to a pre-designated shelter, such as a basement (under a
sturdy piece of furniture) or a Safe Room.
If an
underground shelter is not available, move to a small interior room or hallway
on the lowest floor and get under a sturdy piece of furniture.
Put as
many walls as possible between you and the outside.
Stay
away from windows. Go to the center of the room. Stay away from corners
because they attract debris.
Get out
of automobiles immediately and seek shelter in a nearby building.
If a
building is unavailable or there is no time, get out of the car and lie in a
ditch or low-lying area away from the car.
Be
aware of potential for flooding. In urban or congested areas, never try to
outrun a tornado in a car or truck; instead, leave it immediately for safe
shelter.
Tornadoes
can change direction quickly and can lift up a car or truck and toss it in
the air.
If
caught outside, lie flat in a nearby ditch or depression and cover your head
with your hands. Be aware of potential for flooding.
Be
aware of flying debris. Flying debris from tornadoes causes most fatalities
and injuries.
Mobile
homes, even if tied down, offer little protection from tornadoes.
You
should leave a mobile home and go to the lowest floor of a sturdy nearby
building or a storm shelter.
Avoid
places with wide-span roofs such as auditoriums, cafeterias, large hallways,
or shopping malls.
Do not
open windows, use time to seek shelter.
Use
arms to protect head and neck. |
A bathroom left standing after destruction of the house |
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After the Tornado |
Help
injured or trapped persons. Give first aid when appropriate. Don’t try to move
the seriously injured unless they are in immediate danger of further injury.
Call for help.
Stay
out of damaged buildings. Return home when authorities say it is safe.
Turn on
radio or television to get the latest emergency information. Use the phone only
for emergency calls.
Clean
up spilled flammable liquids immediately. Leave the building if you smell gas or
chemical fumes.
Take
pictures of the damage – both the house and contents – for insurance purposes.
Inspect utilities in a damaged home
Check
for gas leaks – If you smell gas or hear a blowing or hissing noise, open a
window and quickly leave the building. Turn off the gas at the outside main
valve if you can and call the gas company from a neighbor’s home.
If you turn off the gas, a professional must turn it back on.
Look
for electrical damage – If you see sparks or broken or frayed wires, or if
you smell hot insulation, turn off the electricity
at the main fuse box or circuit breaker. If you have to step in water to get
to the fuse box or circuit breaker, call an electrician for advice.
Check
for sewage and water line damage – If you suspect sewage lines are damaged,
avoid using the toilets and call a plumber.
If water pipes are damaged, contact the water company and avoid using water
from the tap. Melt ice cubes for safe water.
Mitigation
Mitigation includes any activities that
prevent an emergency, reduce the chance of an emergency happening, or lessen the
effects of unavoidable emergencies. Investing in preventative mitigation steps
now, such as building a Safe Room, checking local building codes and ordinances
about wind resistant designs and strengthening un-reinforced masonry, will help
reduce the impact of tornadoes in the future.
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You can print or download copies of FEMA publications from
www.fema.gov/library. Order printed copies from FEMA’s DistributionCenter
(800-480-2520). For Taking Shelter Before the Storm, call 888-565-3896. |
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This web page was developed using information resources obtained from the
National Weather Service, Federal Emergency Management Administration, American
Red Cross, and USA Today. Many thanks are due for their efforts in serving the
public. |
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