How does lightning form?
Rapidly rising air in a thunderstorm interacts with rapidly falling air within
the thunderstorm to create separately positive and negative charged areas within
the cloud. Air acts as an insulator, but when the charge builds up to a level
that exceeds its ability to act as an insulator, the result is a spark we see
as lightning. The lightning equalizes the positive and negative charged areas.
Several types of lightning are common:
* In-cloud lightning extends from one charged region of a cloud to another
* Cloud-to-cloud lightning extends between two clouds
* Cloud-to-air lightning extends from a cloud to the air, not touching the ground
* Cloud-to-ground lightning stretches from a cloud to the ground
There are two ways of looking at lightning's direction:
1. Upward streamers: Lightning starts in a cloud when there is an updraft reaching
subfreezing temperatures. A cloud-to-ground flash starts at around 15,000 feet
during summer in the US. It travels toward the ground in 50-yard steps - this
is the downward "leader". At the ground, there are small, upward "streamers" reaching
upwards toward the electrified cloud. When the downward leader connects with
the upward streamer, the bright light that we call lightning is visible, and
moves upward. The way to think of it is that charge is lowered but current
flows upward. This happens in a split second, so it's difficult to see.
2. True ground-to-cloud lightning: In some cases, the cloud area where lightning
usually originates (15,000+ feet high) can be so low, like in a winter storm,
that very tall natural (mountains) or man-made objects (towers or skyscrapers)
sort of interfere with the initial charge moving downward toward the ground.
Instead, the very tall object actually triggers the lightning, and the strike
with its steps, forks, and branches truly appears to go upward. This is an unusual
lightning event that we don't see every day, but there are photos that document
it.
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What causes thunder?
The air in the lightning strike is heated very rapidly and expands, creating
a shock wave we hear as thunder. Thunder lasts a few seconds because we first
hear the shock wave from the portion of lightning closest to us and then we continue
to hear the shock wave from the lightning bolt farther away from us that is reaching
us at later times.
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How far can lightning travel?
Typically, lightning travels 10 miles or less. However, lightning has been observed
to travel 20 miles or more, often extending up to 10 miles away from the cloud
that formed the lightning.
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How hot is lightning?
Within the lightning bolt the air is superheated to temperatures exceeding
50,000°F,
many times hotter than the surface of sun.
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How can I protect my small business and home computers,
TV, and other electronics from lightning?
Lightning damage to small office and home electronics usually occurs
when lightning strikes nearby utility poles or wires, then enters the
building through power,
phone, and TV wires. For direct or indirect hits, the only sure way is to pull
the power, phone, and cable plugs on sensitive electronics before thunderstorms
threaten. The first ever 21st century unplugging solution is StrikeUPS™,
designed specifically for small business and home office environments. StrikeUPS™ automatically
unplugs power & phone connections to eliminate the threat of devastating
loss of data, hardware & equipment such as printers, copiers and fax machines,
due to lightning or other frequent power irregularities. It does not however,
disconnect cable. The Storm Shelter Electronics Corporation will be introducing
a second patented product solution in 2004 designed specifically for the protection
of consumer home entertainment and automation systems – including cable
connections.
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Should I really be concerned about the chances
of being struck by lightning and why is knowing where lightning strikes
more important today?
At any time, 2,000 thunderstorms are occurring around the world, producing
lightning that strikes the earth up to 100 times every second. Every
time it reaches the
earth's surface, it makes an enormous impact, causing power and telecommunications
outages, forest and building fires, damage to aircraft and sensitive electronics,
and deaths. The better we can pinpoint lightning, the better we can reduce
its negative impact. We know that over 20 million flashes strike the
ground in the
United States every year. And most of them hit more than one point on the ground.
While the problems caused by lightning often happen to one person or to one
building at a time, it adds up to cause as much damage and as many casualties
as any other
storm hazard. One of the major reasons why lightning has become more important
in recent years is our tremendous reliance on computers and technology, even
in our homes and small businesses. Today in the information age, irreplaceable
data is at risk. Entire businesses can be reduced to a standstill by the loss
of data that no insurance company can replace. Viewed in this context and with
so much more money due to information lossat stake, the new StrikeUPS™ power
protection device is fast becoming the latest necessity for protecting valuable
small business investments.
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What are the odds of being a lightning victim?
With about 1,000 lightning injuries and deaths each year in the United
States and a population of about 240 million, your the odds are 1 in
240,000 each year.
Over an 80-year lifetime, your chance of being a lightning victim during your
life is 1 in 3,000. You have a about a 1 in 300 chance of being affected by
a lightning death or injury of a close friend or a relative. Now, buildings
and
utility poles are a different story – and these are the primary conduits
for losing valuable electronics and data. There are no hard statistics on the
odds of your small business or home office being “fried”, but the
reasonable and unanimous consensus among prediction experts is that the odds
dramatically increase. Virtually everyone has experienced power outages in
their lives. And statistics point to over a billion dollars in lightning damage
alone
in 2002.
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How does lightning detection work for StrikeUPS™?
The Storm Shelter Electronics Corporation new StrikeUPS™ device uses advanced
lightning detection data through its exclusive agreement with Vaisala-GAI, the
foremost authority and provider of weather data in the world. A sensor detects
a cloud-to-ground flash when five specific criteria are satisfied. These criteria
come from the time series of the electromagnetic signal that is produced by a
typical cloud-to-ground flash over a small portion of a second. When the sensor
observes that these features have been satisfied, it declares that a cloud-to-ground
flash has been detected. This report is combined with similar information from
several other sensors and the data is then used to calculate the flash position.
Storm Shelter receives this data and processes it instantaneously through its
Storm Cell™ network. The Storm CellTM network uses the most advanced digital
paging technology to signal your new StrikeUPS™ unit of the lightning
threat in your area.
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Does sheet lightning pose the same threat as
bolt lightning?
The term sheet lightning generally refers to long channels of lightning
that appear horizontal. This is often seen at the base of clouds in
the 10,000- to
15,000-foot range, and may be at the bottom of a thunderstorm's anvil cloud.
The horizontal--or sheet--portion of the flash may strike the ground some distance
away. Think of the flash as having an upside down "L" shape, where
there is a connection to ground and a long horizontal section along the base
of a cloud. Flashes have been observed by special lightning detection systems
that have one ground strike point that is connected to a horizontal segment
up to 54 miles (90 kilometers) long!
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How many people are struck by lightning?
In the United States, lightning kills 75 to 100 people each year. Lightning safety
experts estimate that there are 10 times as many lightning-related injuries as
deaths, totaling several hundred to a thousand injuries each year. Some of these
injures are reported to authorities; many are not. To find out more, visit the
National Weather Service Natural Hazard Statistics or the Lightning Strike and
Electric Shock Survivors International
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Is it safe to use the telephone during thunderstorms?
Corded telephones are not safe and should not be used during thunderstorms.
The usual way that current enters a telephone is through the wire.
Cloud-to-ground
flashes tend to hit tall objects such as utility poles. When a pole is struck,
its current enters a building through the wiring, then to the phone, and then
straight to your head. Cell phones and cordless phones are safer, but be sure
to stand away from the cordless phone's base as a strong current can possibly
arc a few feet from the base to the handset. There is still a risk of ear damage
from loud static and "pops" associated with cell phone and cordless
phone use during thunderstorms.
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Are headsets safe to use during thunderstorms?
No, is not safe to use any devices that have can conduct electricity from outside
the building to inside the building. That includes telephone headsets, stereo
headsets, TV video games, and your computer's keyboard. Wiring is made to conduct
electricity to you, including lightning's strong electrical current.
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Should I keep all windows in my home closed to keep
lightning from traveling into my house?
It doesn't make much difference if windows are open or closed when
lightning is occurring. It's the window's frame that matters when it
comes to lightning.
If the window frame is metal, lightning current can easily travel through it
and can injure a person touching it. So, it is a bad idea to be touching or
closing them during a thunderstorm. Of course, lightning is Mother
Nature's warning sign
of severe weather. Lightning may not come through your window, but during a
thunderstorm's high winds or microbursts, a patio chair can. So, stay
away from windows. Also,
it used to be recommended that windows should be opened to "equalize pressure" when
a tornado is approaching, this has been proven wrong. Close your windows and
doors at the first signs of approaching thunderstorms.
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What are "positive" and "negative" strikes?
The sign--or polarity--of a lightning strike depends on what type of charge is
lowered to ground. A negative cloud-to-ground flash means that negative charge
is lowered to ground. In this case, excess negative charge occurred aloft in
a thunderstorm, often at about 20,000 feet above sea level, and negative charge
was brought down to the ground by the flash to try to equalize the electrical
imbalance. Usually, the layering of charge is such that negative charge builds
up closer to the ground than positive charge, so negative charge lowers more
readily to the earth's surface. About 95% of all cloud-to-ground flashes worldwide
are negative. In the case of positive charge, the positive charge is brought
to ground, but this usually happens near the end of storms, in winter storms,
and on the edge of large thunderstorm complexes. Although less frequent, positive
strokes generally contain more current and are more apt to catch more people
by surprise.
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Can we use the energy in lightning as an alternate
power source?
Capturing the energy of lightning is intriguing, but not yet feasible for several
reasons. First, no one knows exactly where to collect lightning as it does not
naturally strike specific places more than a few times a year. Next, conventional
storage devices for electricity--like a battery--do not accommodate the magnitude
and duration of a powerful flash that lasts only fractions of a second. Finally,
about half of the energy of a lightning strike dissipates into light, acoustic
energy, and electromagnetic waves. There are ongoing studies to explore the use
of laser beams to control lightning. It appears possible that a laser beam can
be sent into an electrified cloud to trigger lightning which could then be, in
theory, captured.
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Is marine life killed or injured when lightning strikes
in an ocean?
When lightning hits open water, the current is able to travel through the water
quite well. How far away the dangerous current travels is not known, but it's
probably on the order of tens of yards. At and very near the strike point--within
a few yards--current enters the body of a living organization, resulting in injury
or death. At greater distances, the effects are less, so that the current might
stun an organism but not kill it. There are few reports of massive fish kills.
It may be that there are not too many fish in any single volume in the affected
water, they may recover quickly, or maybe larger fish eat the incapacitated fish.
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Why is the launch of the shuttle delayed because
of bad weather, when commercial airliners take off and land in thunderstorms
and lightning?
The shuttle is quite different from a commercial airliner. The shuttle launches
straight up through any clouds that are there. Airliners sometimes fly through
clouds, but they can avoid the worst ones. Rocket exhaust plumes stretching from
the shuttle (or other rockets) to the ground makes an excellent lightning rod
and therefore lightning is drawn especially to a flying rocket. This is very
dangerous. The shuttle has a fragile and critical thermal tile skin that must
be intact for re-entry. Lightning strikes would probably shatter thermal tiles.
The shuttle also uses extremely explosive hydrogen and oxygen for fuel. A lightning
strike on or near the launch pad or during flight could cause this propellant
to explode. An airliner uses a kerosene-like fuel which is far less flammable.
Airliners can land in the rain, but even they often delay or divert to avoid
severe thunderstorms.
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How can you tell how far away lightning is?
It takes five seconds for sound to travel one mile. When you see a flash, count
the number of seconds between until you hear the thunder and then divide by five
to get the number of miles between the lightning and you. National lightning
safety experts agree a good rule of thumb is if you count 30 seconds or less
between the flash and thunder, you are in immediate danger and should seek safety.
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Do tires in a car or rubber soles on shoes protect
you from lightning?
No. The lightning has traveled many miles to reach you; the extra inch of rubber
offers no protection. The inside of a car is safer because the lightning travels
around the car's metal frame to the ground. Rubber soles on shoes offer no protection
from lightning.
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How can I protect myself from lightning?
People who spend much of their time outside are most at risk being struck by
lightning. Golfers, fishermen, and hikers are most prone to being struck. Anyone
who works outside, such as a construction worker, is also at risk. You can avoid
being struck by immediately seeking shelter inside a substantial building or
metal-topped vehicle when lightning is present. Never seek shelter outside under
a tree. It's better to be wet from rain than dead or disabled by lightning. When
inside and lightning is nearby, do not use electrical appliances, including computers
and video games connected TV sets, telephones, or have contact with running water
or water pipes. Electricity from lightning can travel through phone wires, electric
wires, TV cables, and plumbing.
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If I can't reach shelter how do I protect myself?
As a last resort, make yourself as short as possible with as little contact with
the ground as possible. Lightning usually strikes the tallest objects such as
trees, utility poles, and metal objects. Do not seek shelter under trees, utility
poles, near metal fences or gates. Go to a low spot, but avoid washes and places
where water will collect, crouch down on the balls of your feet and make yourself
into as small a ball as you can. Do not lay down or sit on the ground. Lightning
currents can travel across the ground so you want to make as little contact with
the ground as possible.
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How close to a thunderstorm can you be and remain
safe?
In urban areas, buildings and city noise reduce your ability to hear thunder
until it's only 10 miles away or less. Since lightning can easily travel 10 miles
away from a thunderstorm, if you're in a city and can hear thunder, you are at
risk from being hit by lightning. In quiet, rural areas, thunder can be heard
from thunderstorms that are up to 15 or more miles away. The best course of action
is to remain alert to your weather surroundings. Be aware of new thunderstorms
forming near you as other thunderstorms are leaving the area.
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Where does the most lightning occur in the United States?
Year in and year out, the hot spot for the most lightning per square mile is
in central Florida. Other lightning hot spots vary from year to year, but in
Gulf Coast areas of northwest Florida, Alabama, Mississippi, Louisiana, and east-central
Texas usually trail central Florida in strike density.
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Is there much lightning in tornadoes and hurricanes?
Tornadoes can have a wide variety of lightning. Some closely-observed tornadoes
had no thunder at all from the storm during the tornado. But usually, the parent
storm eventually produces a fair amount of lightning. Hurricanes usually have
very little or no lightning. The only significant lightning is observed in the
outer rain bands. Probably less than 10% have more than a few cloud-to-ground
flashes in the eye wall. Data on in-cloud flashes during hurricanes is scarce.
Why there is so little lightning in the core of hurricanes has been the subject
of conjecture. It probably has to do with the strong horizontal winds not allowing
much vertical mixing compared to a more isolated storm.
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Is lightning attracted to water or other objects
on the ground?
A cloud-to-ground flash usually begins in a cloud at 15,000 to 20,000 feet above
ground. It comes to earth in 50-yard steps. Until it's close to the ground, it
has no idea of what it will hit. Then, within 30 to 50 yards of the ground, lightning
decides what is the best connection to make with the surface. Often, the best
connection is the tallest object within the 30 to 50 yard area.
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