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How
is lighting formed?
(Part 1)
Ice crystals at the top of the cloud accumulate positive charges; rain
drops in the bottom half of the cloud consist mostly of negative charges;
the ground below the cloud becomes positively charged. The separation
in charges within the cloud is produced by rapidly rising air, called
updrafts, interacting with precipitation moving downward within the cloud.
The stronger the updrafts, the greater the electrical potential developed.
Lightning flashes when the attraction between positive and negative charges
becomes strong enough to overcome the air's high resistance to electrical
flow. The entire process takes less than a second, and this is how it
happens.
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Lightning
Safety Tips
Some
thunderstorms can be seen approaching, while others hit without warning.
It is important to learn and recognize the danger signs. To
be the safest, "Seek safe shelter Indoors immediately!"
"Danger
signs"
Distant lightning and thunder.
Dark, towering, or threatening clouds or visible cloud bursts.
Severe Thunderstorm Watches and Warnings are issued by the NWS.
(A severe thunderstorm watch is when the weather conditions are such that
a severe thunderstorm damaging winds 58 miles per hour or more, or hail
three-fourths of an inch in diameter or greater is likely to develop.)
(A severe thunderstorm warning is issued when a severe thunderstorm has
been sighted by watchers or indicated by weather radar.)
"When
Indoors"
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. Listen to a battery
operated radio or television for the latest storm information Stand clear
from windows, doors and electrical appliances. Unplug appliances well
before a storm nears - never during. Avoid bathtubs, water faucets, and
sinks because metal pipes can transmit electricity. Do not use the telephone
except for emergencies.
L lightning can follow the electrical and phone lines.
When Outdoors:
Look for, and get in a hard topped car.
Never use a tree as a shelter.
Avoid areas that are higher than the surrounding landscape.
Keep away from metal objects including
bikes, golf carts, fencing, machinery, etc.
Avoid tall structures such as towers, tall trees,
fences, telephone lines, or power lines.
Stay away from natural lightning rods such as golf clubs,
tractors, fishing rods, bicycles, or camping equipment.
Be aware of the potential for flooding in low-lying areas.
Immediately get out and away from pools, lakes,
and other bodies of water.
Removing all metal objects from your person is recommended.
Don't stand in a crowd of people. - "Spread out"
If you feel a tingling sensation, your hair stands on end or you hear
'buzzing' from nearby rocks, fences, etc., move immediately.
Lightning may be about to strike!
Immediately crouch down, get on the balls of your feet
and cover your ears.
Do not lie down or place your hands on the ground.
What
to do if you or someone around
you is struck by Lightning?
If the victim is burned, provide first
aid and call 911 immediately. Look for burns where Lightning entered and
exited the body. If the strike cause the victim's heart and breathing
to stop, give cardiopulmonary resuscitation (CPR) until medical professionals
arrive and take over.
"Prepare
for an emergency"
Have disaster supplies on hand Flashlight
with extra batteries Portable, battery-operated radio and extra batteries
First aid kit and manual Emergency food and water, Nonelectric can opener,
Essential medicines, Cash and credit cards. Dead or rotting trees and
branches can fall during a severe thunderstorm and cause injury and damage.
Teach family members how and when to turn off gas, electricity and water.
Teach children how and when to call 9-1-1, police, fire department, and
which radio station to tune for emergency information. Develop an emergency
communication plan. In case family members are separated from one another
during a thunderstorm (a real possibility during the day when adults are
at work and children are at school), have a plan for getting back together.
Ask an out-of-state relative or friend to serve as the "family contact".
After a disaster, it's often easier to call long distance. Make sure everyone
knows the name, address, and phone number of the contact person.
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National
Lightning Safety Institute (NLSI)
Lightning
Strikes & The Effects On Humans
By William T.
Hark, MD
Doswell's
Do's & Don'ts
Lightning
Facts, Myths Miracles and Mirages
By Mary Ann Cooper MD
How
is lighting formed?
(Part 2)
The
Lightning stroke originates from negatively charged "step leaders" at
the base of a thunderstorm cloud. These step leaders surge downward
150 feet at a time, sometimes more horizontally than vertically, attempting
to complete a channel to the ground. Electrical charges separate within
the cloud; positive charges accumulate at the top of the cloud, negative
charges at the base of the cloud. The negatively charged cloud base
induces a positive charge at ground level. The negatively charged electrons
begin to descend in a zigzagging pattern. This is the "step leader."
As the "step leader" nears the ground, it draws a positively charged
"streamer" upward. This "streamer" is normally drawn from the tallest
nearby object. As the "step leader" and "streamer" connect, a powerful
electrical current begins flowing downward. When the step leader is
close to the ground, one or more positively charged "streamers" are
pulled upward, usually from a tallest item in the vicinity (for example:
trees, buildings, flag poles, golfers). The last surge of a step leader
completes the electrical channel with the ground and the Lightning stroke
becomes visible. The light seen is the return stroke, an intense wave
of positive charge that travels upward about 60,000 miles per hour.
The process can repeat several times along the same path in less than
half a second, making Lightning appear to flicker.
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