General Information About Lightning
Each year, hundreds of Americans are hit by lightning, resulting
in dozens of deaths and injuries. In fact, lightning causes more
deaths per year in the United States than those from tornadoes or
hurricanes.
Average
U.S. Deaths Per Year
(Based on 30-Year Normals)
|
Floods
Lightning
Tornadoes
Hurricanes
|
140
90
80
30 |
In addition, lightning sparks thousands of fires and causes millions
of dollars in damage to homes and businesses each year in the United
States.
In Utah, lightning is the number one killer among weather phenomena:
Utah Deaths
From Weather Phenomena
(January 1950 - August 2003)
Lightning
57
Flash Floods 26
Tornadoes 1
Briefly described, lightning is a massive electrical discharge,
caused by the flow of electrons between oppositely charged parts
of a cumulonimbus (thunderstorm) cloud or between the cloud and
the ground. It's formed when clouds become electrically polarized--with
a net positive charge near the top of the cloud and net negative
charge in the lower part of the cloud. Exactly how this polarization
occurs is still a mystery. However, a number of researchers suggest
that a channel of electrons--called a stepped leader--sometimes
flows out a cloud and moves towards the ground. The approach of
this leader increases the ground's positive charge and draws a similar
stream of positively charged electrons--called a pilot streamer--upwards.
When the leader and streamer meet, a closed circuit is created and
electrical current begins to flow. Electrons are discharged onto
the ground and an upward moving return stroke heats the air and
makes lightning visible.
Lightning is very powerful. It can discharge millions of volts of
electricity, propel return strokes at nearly the speed of light,
and heat surrounding air up to thousands of degrees Fahrenheit.
When this superheated air explodes away from the electrical current
it creates a shock wave called "thunder."
Lightning is extremely dangerous, highly unpredictable and very
fickle. It can strike and destroy one object without touching another
one nearby; or it can hit an object and travel across the ground
for dozens of feet electrocuting anything in its path.
Here are five interesting facts about the affect of lightning on
people and objects:
In 1991,
lightning killed 73 people in the United States with five times
as many males as females killed by lightning. The 10-39 age group
tended to be the most susceptible to the dangers of lightning with
62% of the fatalities falling into that range. Also, 21 people perished
standing under a tree, 12 died out in the open, and 10 in a boat.
Lightning
does strike the same place twice. The Empire State Building in New
York City is struck on the average of about 23 times per year.
On September
1, 1939, lightning hit and killed 835 sheep on the top of Pine Canyon
in the Raft River Mountains of Box Elder County, Utah.
On June 28,
1956, a lightning bolt struck the top of a home in Cedar City, Utah,
leaving a 10-foot wide hole in the roof.
On May 30,
1987, a giant coal truck (having tires seven feet tall) was hit
by lightning at a strip mine near Providence, Kentucky. The six-wheel,
177,000 pound truck "felt like it had been picked up and set
down, and shook all over." One of the six $4,000 steel-belted
tires was blown from the rim and landed 30 feet away, another was
turned inside out and a third went flat, leaving only one of the
four rear tires intact. (Contrary to popular belief, the "rubber
tires" of a car or truck do NOT protect people from lightning.
Instead, the metal covering of the vehicle usually protects the
occupants by conducting the electrical discharge across the vehicle
and down into the ground.)
Lightning
Safety Rules
Lightning normally strikes the tallest object in an area, and is
particularly attracted to metal and objects near or on water. In
other words, lightning loves three things: height, metal and water.
Also history has shown that lightning's most likely targets are
tall, isolated structures that are close to water, such as hilltops,
swimming pools and lakes. These safety rules will help save your
life:
- If inside a building or a metal-enclosed vehicle, remain inside.
- Inside a home, avoid using telephones and electrical appliances.
- If outside, seek cover in a large enclosed building or metal-enclosed
vehicle.
- If outside and there is not time to reach a large enclosed
building or metal-enclosed vehicle, follow
these rules:
- Do not stand underneath a natural lightning rod such as
an isolated tree (move away from any tree a distance that
is twice the height of the tree).
- Avoid projecting above the surrounding landscape as you
would if you were standing on a hilltop, in an open field,
on a beach, or fishing in a small, open boat.
- Get out of and away from open water.
- Get away from metallic equipment.
- Get off of and away from motorcycles, scooters, golf carts,
bicycles, and tractors without enclosed cabs.
- Put down golf clubs.
- Stay away from wire fences, clotheslines, metal pipes,
metal rails, and other metallic conductors that can carry
lightning to you from some distance away.
- Avoid seeking shelter in small, isolated sheds or other
structures in open areas.
- If in a forest, seek shelter in a low area under a thick
growth of small trees.
- In open areas, go to a low place such as a ravine or gully,
but be alert for flash floods.
- If you are isolated in a level, open area and you feel
your hair stand on end (indicating that lightning is about
to strike), drop to your knees and bend forward putting your
hands on your knees and your chin to you chest. Do NOT lie
flat on the ground.
Much of the information for this section originally appeared in
the copyrighted book Utah's Weather and Climate, edited by
Dan Pope and Clayton Brough, in 1996. UCCW Directors have received
permission from the copyright owners of this book to reproduce such
information on its website and to revise and updated it where appropriate.
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