|
Severe Thunderstorm
Severe Thunderstorm in PDF
Format -- 62 KB
Produced by the National Disaster Education Coalition:
American Red Cross, FEMA, IAEM, IBHS, NFPA, NWS, USDA/CSREES, and
USGS.
|
|
Why Talk About Severe Thunderstorms?
Despite their small size, all thunderstorms are dangerous. Every thunderstorm
produces lightning, which kills more people each year than tornadoes.
Heavy rain from thunderstorms can lead to flash flooding. Strong winds,
hail, and tornadoes are also dangers associated with some thunderstorms.
Thunderstorms affect relatively small areas when compared with hurricanes
and winter storms. The typical thunderstorm is 15 miles in diameter and
lasts an average of 20 to 30 minutes. Of the estimated 100,000 thunderstorms
that occur each year in the United States, only about 10 percent are classified
as severe.
All thunderstorms are dangerous. Every thunderstorm
produces lightning, which kills more people each year than tornadoes. Heavy
rain from thunderstorms can lead to flash flooding.
[Back to Top]
What Are Severe Thunderstorms, and What Causes Them?
The National
Weather Service (NWS) considers a thunderstorm severe if it produces
hail at least three-quarters of an inch in diameter, has winds of 58 miles
per hour or higher, or produces a tornado. When a severe thunderstorm
WARNING is issued, review what actions to take under a tornado
warning or a flash flood warning.
Thunderstorms may occur singly, in clusters, or in lines. Some of the
most severe weather occurs when a single thunderstorm affects one location
for an extended time. Lightning is a major threat during a thunderstorm.
It is the lightning that produces thunder in a thunderstorm. Lightning
is very unpredictable, which increases the risk to individuals and property.
In the United States, 75 to 100 people are killed each year by lightning,
although most lightning victims do survive. Persons struck by lightning
often report a variety of long-term, debilitating symptoms, including
memory loss, attention deficits, sleep disorders, numbness, dizziness,
stiffness in joints, irritability, fatigue, weakness, muscle spasms, depression,
and an inability to sit for long. It is a myth that lightning never strikes
the same place twice. In fact, lightning will strike several times in
the same place in the course of one discharge.
Learn more about severe thunderstorm risk in your area. Contact your
local emergency management office, National Weather Service (NWS) office,
or American
Red Cross chapter.
[Back to Top]
Awareness Information
- A National Weather Service WATCH is a message indicating that conditions
favor the occurrence of a certain type of hazardous weather. For example,
a severe thunderstorm watch means that a severe thunderstorm is expected
in the next six hours or so within an area approximately 120 to 150
miles wide and 300 to 400 miles long (36,000 to 60,000 square miles).
The NWS Storm Prediction Center issues such watches. Local NWS forecast
offices issue other watches (flash flood, winter weather, etc.) 12
to 36 hours in advance of a possible hazardous- weather or flooding
event. Each local forecast office usually covers a state or a portion
of a state.
- An NWS WARNING indicates that a hazardous event is occurring or is
imminent in about 30 minutes to an hour. Local NWS forecast offices
issue warnings on a county-by-county basis.
Lightning often strikes outside of heavy rain and may occur as far
as 10 miles away from any rainfall. "Heat lightning" is actually lightning
from a thunderstorm too far away for thunder to be heard. However, the
storm may be moving in your direction.
You are in danger from lightning if you can hear thunder. Because
light travels so much faster than sound, lightning flashes can sometimes
be seen long before the resulting thunder is heard. When the lightning
and thunder occur very close to one another, the lightning is striking
nearby. To estimate the number of miles you are from a thunderstorm, count
the number of seconds between a flash of lightning and the next clap of
thunder. Divide this number by five.
Many strong thunderstorms produce hail. Large hail, or flying
glass it mayhave broken, can injure people and animals. Hail can be smaller
than a pea, or as large as a softball, and can be very destructive to
automobiles, glass surfaces (skylights and windows), roofs, plants, and
crops. In a hailstorm, take cover immediately. Pets and livestock are
particularly vulnerable to hail, so bring animals into shelter before
storms begin.
Downbursts and straight-line winds associated with thunderstorms
can produce winds 100 to 150 miles per hour, enough to flip cars, vans,
and semitrucks. The resulting damage can equal the damage of most
tornadoes. If a severe thunderstorm warning is issued, take shelter the
same way you would if a tornado were approaching your area. Leave structures
that are susceptible to being blown over in high winds, such as a mobile
home.
[Back to Top]
Plan for a Thunderstorm
Develop a Family Disaster Plan. Please see the
"Family Disaster Plan"section for general family planning information.
Severe thunderstorm specific planning should include the following:
- Learn about your area's severe thunderstorm risk. Severe thunderstorms
can occur year-round and at any hour. Contact your local emergency
management office, local National Weather Service office, or American
Red Cross chapter for more information.
- Discuss how you would know if a thunderstorm may produce a tornado.
Tornadoes develop from severe thunderstorms along and ahead of cold
fronts. (See the "Tornado" section for more
information.)
- Pick a "safe place" in your home where family members can gather
during a thunderstorm. This should be a place where there are
no windows, skylights, or glass doors, which could be broken by strong
winds or hail, causing damage or injury. Severe thunderstorms do,
at times, produce tornadoes.
- In preparation for possible tornado warnings, consider making your
severe thunderstorm "safe place" on the lowest floor of the building,
near your tornado safe space.
- Learn how to squat low to the ground. Make yourself the smallest
target possible for lightning and minimize contact with the ground.
Lightning current often enters a victim through the ground rather
than by a direct overhead strike. Assume a crouched position on the
ground with only the balls of the feet touching the ground, place
your hands on your knees, and lower your head. Minimize your body's
surface area, and minimize contact with the ground.
- Discuss how you would be warned of an approaching thunderstorm.
Different communities have different ways of providing warnings. Many
communities have sirens intended for outdoor warning purposes. Use
a NOAA Weather Radio with a tone-alert feature to keep you aware of
watches and warnings while you are indoors. Learn about your community's
warning system. Make sure all family members know the name of the
county or parish where you live or are traveling, because severe thunderstorm
watches and warnings are issued for counties or parishes.
- Get training. Take an American Red Cross first aid and CPR
course to learn how to treat burns and how to give rescue breathing
and administer CPR. Everyone should know how to respond, because severe
thunderstorms can strike almost anywhere at anytime.
- Discuss severe thunderstorms with your family. Everyone should
know what to do in case all family members are not together. Discuss-ing
disaster ahead of time helps reduce fear and lets everyone know how
to respond during a severe thunderstorm.
[Back to Top]
What to Tell Children
The sound of thunder can be especially frightening for young children.
Take the "scariness" away by teaching them what to expect during a thunderstorm
and how to be safe.
- Postpone outdoor activities if thunderstorms are likely. Many
people take shelter from the rain, but most people struck by lightning
are not in the rain! Postponing activities is your best way to avoid
being caught in a dangerous situation.
- If you see or hear a thunderstorm coming, go inside a sturdy building
or car. Sturdy buildings are the safest place to be. If no building
is nearby, a hard-top vehicle will offer some protection. Keep car
windows closed and avoid convertibles. Rubber-soled shoes and rubber
tires provide no protection from lightning. However, the steel frame
of a hard-topped vehicle provides increased protection if you are
not touching metal. Although you may be injured if lightning strikes
your car, you are much safer inside a vehicle than outside.
- If you can't get inside, or if you feel your hair stand on end,
which means lightning is about to strike, hurry to a low, open space
immediately. Crouch down on the balls of your feet, place your hands
on your knees and lower your head. Make yourself the smallest
target possible and minimize contact with the ground.
- Practice the "crouch down" position. Show children how to
practice squatting low to the ground to be the smallest target possible
for lightning in case they get caught outside in a thunderstorm. Show
them how to place their hands on their knees and lower their head,
crouching on the balls of their feet.
- Stay away from tall things like trees, towers, fences, telephone
lines, or power lines. They attract lightning. Never stand underneath
a single large tree out in the open, because lightning usually strikes
the highest point in an area.
- Stay away from metal things that lightning may strike, such as
umbrellas, baseball bats, fishing rods, camping equipment, and bicycles.
Lightning is attracted to metal and poles or rods.
- If you are boating or swimming, get to land immediately. Stay
away from rivers, lakes, and other bodies of water and get off the
beach. The saturated sand conducts electricity very well. Water is
an excellent conductor of electricity. When lightning strikes nearby,
the electrical charge can travel through the water. Each year people
are killed by nearby lightning strikes while in or on the water or
on the beach.
- Turn off the air conditioner and television, and stay off the
phone until the storm is over. Lightning can cause electric appliances,
including televisions and telephones, to become dangerous during a
thunderstorm.
- Stay away from running water inside the house; avoid washing your
hands or taking a bath or shower. Electricity from lightning has
been known to come inside through plumbing.
Assemble a Disaster Supplies Kit
Please see the section "Disaster Supplies Kit"
for general supplies kit information. Severe Thunderstorm - specific supplies
should include the Disaster Suplies Kit basics.
[Back to Top]
How to Protect Your Property
- Make a list of items to bring inside in the event of a storm.
Having a list will help you remember things that may be broken or
blown away in strong winds.
- Keep trees and shrubbery trimmed. Make trees more wind resistant
by removing diseased or damaged limbs, then strategically remove branches
so that wind can blow through. Strong winds frequently break weak
limbs and hurl them at great speed, causing damage or injury when
they hit.
- Remove any debris or loose items in your yard. Branches and
firewood may become missiles in strong winds.
- Consider installing permanent shutters to cover windows. Shutters
can be closed quickly and provide the safest protection for windows.
- Install lightning rods. Lightning rods will carry the electrical
charge of lightning bolts safely to the ground, greatly reducing the
chance of a lightning-induced fire.
- Insure crops against financial loss from storm damage through
the Federal Crop Insurance Corporation of the U.S. Department of Agriculture.
If applicable, it is recommended you obtain separate specific insurance
to cover your crops. Losses are not covered through usual insurance
policies. Each year severe storms cause millions of dollars in crop
damage. Hail, in particular, has been known to wipe out entire fields.
[Back to Top]
Media and Community Education Ideas
- Publish a special section in your local newspaper with emergency
information about thunderstorms and lightning. Place special emphasis
on what people should do if they are caught outside. Localize the
information by printing the phone numbers of local emergency service
offices, the American Red Cross chapter, and the nearest hospitals.
- Interview officials with the
U.S. Department of Agriculture about the Federal
Crop Insurance Corporation.
- Periodically inform your community of local public warning systems.
- Have your meteorologist speak to elementary schools and youth groups
about the dangers of thunderstorms, lightning, and hail.
- Interview a representative of the American Red Cross about giving
first aid to people who have been struck by lightning.
- Interview agents from various insurance companies about what homeowner's
insurance does and does not cover in severe weather (flooding, fallen
trees creating no structural damage, etc.).
[Back to Top]
What to Do Before a Thunderstorm
- Use a NOAA Weather Radio with a tone-alert feature to keep you
informed of watches and warnings issued in your area. The tone-
alert feature will automatically alert you when a watch or warning
is issued.
- If planning a trip or extended period of time outdoors, listen
to the latest forecasts and take necessary action if threatening weather
is possible. Knowing what weather could happen helps you be prepared
to respond if necessary. Having a raincoat, umbrella, and disaster
supplies kit available will make it easier to deal with severe weather
if it occurs.
- Postpone outdoor activities if thunderstorms are imminent. Coaches
of outdoor sports teams should have a NOAA Weather Radio with a tone-alert
feature during practice sessions and games. Threatening weather
can endanger athletes, staff, and spectators. Many people take shelter
from the rain, but most people struck by lightning are not in the
rain! Postponing activities is your best way to avoid being caught
in a dangerous situation.
- Keep an eye on the sky. Pay attention to weather clues around
you that may warn of imminent danger. Look for darkening skies, flashes
of lightning, or increasing wind, which may be signs of an approaching
thunderstorm.
- Stay aware of your surroundings. Look for places you might
go should severe weather threaten.
- Listen for the sound of thunder. If you can hear thunder,
you are close enough to the storm to be struck by lightning. Go to
safe shelter immediately.
[Back to Top]
What to Do During a Severe Thunderstorm WATCH
- Listen to a NOAA Weather Radio, or local radio or television stations
for updated information. Local authorities will provide you with
the best information for your particular situation.
- Avoid natural lightning rods such as golf clubs, fishing poles,
tractors, bicycles, and camping equipment. Lightning is attracted
to metal and poles or rods.
- Be prepared to seek shelter if a severe thunderstorm approaches.
A sturdy building is the safest place to be during a severe thunderstorm.
Avoid unprotected gazebos, rain or picnic shelters, golf carts, baseball
dugouts and bleachers. While many people take shelter from rain in
these locations, they are often isolated structures in otherwise open
areas, and, therefore, a target for lightning. In addition, gazebos
and picnic shelters are often poorly anchored and subject to being
uprooted and blown around in strong thunderstorm winds. They also
offer little protection from large hail.
If you perceive a severe thunderstorm approaching:
- Secure outdoor objects such as lawn furniture that could blow
away or cause damage or injury. Take light objects inside.
- Shutter windows securely and brace outside doors. This will
help protect your house from damaging winds or flying debris.
- Avoid electrical equipment and telephones. Lightning could
follow the wire. Television sets are particularly dangerous at this
time.
- Avoid bathtubs, water faucets, and sinks because metal pipes can
transmit electricity.
[Back to Top]
What to Do During a Severe Thunderstorm WARNING
Listen to a NOAA Weather Radio or a battery-powered radio or television
for updated emergency information. If the power goes out, you still will
have access to important information.
[Back to Top]
What to Do at Home During a Thunderstorm WARNING
- Draw blinds and shades over windows. If windows break due
to objects blown by the wind or large hail, the shades will help prevent
glass from shattering into your home.
- Unplug appliances. Avoid using the telephone or any electrical
appliances. If lightning strikes, telephone lines and metal pipes
can conduct electricity. Leaving electric lights on, however, does
not increase the chances of your home being struck by lightning.
- Avoid taking a bath or shower, or running water for any other
purpose. Metal pipes and plumbing can conduct electricity if struck
by lightning.
- Turn off the air conditioner. Power surges from lightning
can overload the compressor, resulting in a costly repair job.
[Back to Top]
What to Do if You Are Outside and a Severe Thunderstorm Is Approaching
- If you are boating or swimming, get to land, get off the beach,
and find shelter immediately. Stay away from rivers, lakes, and
other bodies of water. Water is an excellent conductor of electricity.
When lightning strikes nearby, the electrical charge can travel through
the water. Each year, numbers of people are killed by nearby lightning
strikes while in or on the water.
- Take shelter in substantial, permanent, enclosed structures, such
as reinforced buildings. Sturdy buildings are the safest place
to be. Avoid unprotected gazebos, rain or picnic shelters, golf carts,
baseball dugouts and bleachers. While many people take shelter from
rain in these locations, they are often isolated structures in otherwise
open areas, and, therefore, a target for lightning. In addition, gazebos
and picnic shelters are often poorly anchored and subject to being
uprooted and blown around in strong thunderstorm winds. They also
offer little protection from large hail.
- If there are no reinforced buildings in sight, take shelter in
a car. Keep car windows closed and avoid convertibles. Rubber-soled
shoes and rubber tires provide no protection from lightning. However,
the steel frame of a hard-topped vehicle provides increased protection
if you are not touching metal. Although you may be injured if lightning
strikes your car, you are much safer inside a vehicle than outside.
- If you are in the woods, find an area protected by a low clump
of trees. Never stand underneath a single large tree in the open.
Be aware of the potential for flooding in low-lying areas.
- As a last resort and if no structure is available, go to a low-
lying, open place away from trees, poles, or metal objects. Make sure
the place you pick is not subject to flooding. Have as little
contact with the ground as possible. Squat low to the ground. Place
your hands on your knees with your head between them. Make yourself
the smallest target possible. Do not lie flat on the ground this will
make you a larger target.
- Avoid tall structures such as towers, tall trees, fences, telephone
lines, and power lines. Lightning strikes the tallest objects
in an area.
- Stay away from natural lightning rods, such as golf clubs, tractors,
fishing rods, bicycles, and camping equipment. Lightning is attracted
to metal and poles or rods.
- If you are isolated in a level field or prairie and you feel your
hair stand on end (which indicates that lightning is about to strike),
drop to your knees and bend forward, putting your hands on your knees.
Crouch on the balls of your feet. Do not lie flat on the ground.
The electrical build-up just before lightning strikes will cause your
hair to stand on end. Make yourself the smallest target possible and
minimize contact with the ground.
[Back to Top]
What to Do While driving During a Thunderstorm and Heavy Rain
- Pull safely onto the shoulder of the road and stop, making sure
you are away from any trees or other tall objects that could fall
on the vehicle. Stay in the car and turn on the emergency flashers
until the heavy rains subside. Heavy rains produced by thunderstorms
can greatly reduce visibility. Vehicles will provide better protection
from lightning than being out in the open. Emergency flashers will
alert other drivers with limited visibility that you have stopped.
Keep car windows closed.
- Avoid contact with metal or conducting surfaces outside or inside
the vehicle. Lightning that strikes nearby can travel through
wet ground to your car. The steel frame of a hard-topped vehicle provides
increased protection if you are not touching metal. Rubber tires provide
no protection from lightning. Avoid contact with potential conductors
to reduce your chance of being shocked. Although you may be injured
if lightning strikes your car, you are much safer inside a vehicle
than outside.
- Avoid flooded roadways. Most flood fatalities are caused by
people attempting to drive through water, or people playing in high
water. The depth of water is not always obvious. The roadbed may be
washed out under the water, and you could be stranded or trapped.
Rapidly rising water may stall the engine, engulf the vehicle and
its occupants, and sweep them away. Look out for flooding at highway
dips, bridges, and low areas. Two feet of water will carry away most
automobiles.
[Back to Top]
What to Do After a Thunderstorm
- Continue listening to local radio or television stations or a
NOAA Weather Radio for updated information and instructions. Access
may be limited to some parts of the community, or roads may be blocked.
- Help a neighbor who may require special assistance - infants,
elderly people, and people with disabilities. Elderly people and
people with disabilities may require additional assistance. People
who care for them or who have large families may need additional assistance
caring for several people in emergency situations.
- Stay away from storm-damaged areas. You may be putting yourself
at further risk from the residual effects of severe thunderstorms.
- Watch out for fallen power lines and report them immediately.
Reporting potential hazards will get the utilities turned off as quickly
as possible, preventing further hazard and injury.
[Back to Top]
What to Do if Someone Is Struck by Lightning
- Call for help. Get someone to dial 9-1-1 or your local Emergency
Medical Services (EMS) number. Medical attention is needed as quickly
as possible.
- Give first aid. If breathing has stopped, begin rescue breathing.
If the heart has stopped beating, a trained person should give CPR.
If the person has a pulse and is breathing, look and care for other
possible injuries.
- Check for burns in two places. The injured person has received
an electrical shock and may be burned, both where they were struck
and where the electricity left their body. Being struck by lightning
can also cause nervous system damage, broken bones, and loss of hearing
or eyesight. People struck by lightning carry no electrical charge
that can shock other people, and they can be handled safely.
[Back to Top]
|
|