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What
is a Lightning?
Lightning is an atmospheric discharge of electricity,
which typically occurs during thunderstorms, and sometimes
during volcanic eruptions or dust storms. In the atmospheric
electrical discharge, a leader of a bolt of lightning
can travel at speeds of 60,000 m/s, and can reach temperatures
approaching 30,000 °C (54,000 °F), hot enough
to fuse silica sand into petrified lightning, known scientifically
as glass channels or fulgurites which are normally hollow
and can extend some distance into the ground. There are
some 16 million lightning storms in the world every year.
For an American, the chance of being struck by lightning
is approximately 576,000 to 1 and the chance of actually
being killed by lightning is approximately 2,320,000 to
1.
Lightning
can also occur within the ash clouds from volcanic eruptions,
or can be caused by violent forest fires which generate
sufficient dust to create a static charge.
How
lightning initially forms is still a matter of debate:
Scientists have studied root causes ranging from atmospheric
perturbations (wind, humidity, friction, and atmospheric
pressure) to the impact of solar wind and accumulation
of charged solar particles. Ice inside a cloud is thought
to be a key element in lightning development, and may
cause a forcible separation of positive and negative charges
within the cloud, thus assisting in the formation of lightning.
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Tips:
Determine the danger:
If
you are outdoors when you see or hear a thunderstorm coming
or your hair stands on end, immediately stop your activities
and seek safe shelter immediately!
Flash-to-bang:
When
you see the FLASH
Count the seconds to the BANG
Every 5 seconds equals 1 mile. Divide by 5 to give the
distance in miles from you to the lightning.
30 seconds - suspend all outdoor activities (lightning
strike was 6 miles away or less) and seek safe shelter.
If you count 15 seconds or less, a lightning strike could
occur where you are (3 miles away or less).
Outdoor safety:
Postpone
outdoor activities if thunderstorms are imminent.
Move to a sturdy enclosed building.
Get inside a hardtop vehicle and keep the windows rolled
up. Avoid touching any metal.
If caught outdoors and no
shelter is nearby:
Stay
away from tall trees. If there is no shelter crouch in
the open, keeping twice as far away from a tree as it
is tall.
Avoid being the tallest object around. Get as low as you
can but do not lie prone on the ground. Squat on the balls
of your feet to have minimum contact with the ground.
Place your hands over your ears and your head between
your knees.
Get below tree line if you are in the mountains and into
a grove of SMALL trees.
Toss metal golf clubs, fishing rods, tennis rackets, tools,
walking sticks, backpacks with metal or any other metal
objects away from you. You can be burned by them.
Get out of the water. If caught in a boat, crouch down
in the center of the boat away from metal hardware. Swimming,
wading, snorkeling and scuba diving are NOT safe. Don't
stand in puddles, even if wearing rubber boots.
Move away from a group of people. Stay several yards away
from each other. Don't share a bleacher bench or huddle
in a group.
Avoid open fields, high places, trees (especially isolated
trees), water, unprotected gazebos or picnic shelters,
baseball dugouts, communications towers, flag poles and
light poles, metal or wood bleachers, metal fences, convertibles,
golf carts, bicycles, and motorcycles.
Indoor
safety:
Utility
lines and metal pipes can conduct electricity.
Do
not use any electrical appliances (except those used for
weather information) and unplug unnecessary ones.
Turn off air conditioners and computers to protect them
from power surges.
Do not use a corded telephone except in an emergency.
Do not bathe or shower during a thunderstorm.
Avoid contact with anything that conducts electricity
Stay away from windows and doors.
Avoid contact with concrete walls or floors which may
contain metal reinforcing bars; carports or open garages;
covered patios; washing your hands or doing dishes.
No place is completely safe from lightning, but some places
are safer than others. Although some victims are struck
directly by the main lightning stroke, many victims are
struck as the current moves in and along the ground.
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2008 - Department of Meteorology, 383, Bauddhaloka Mawatha, Colombo
07, Sri Lanka. |
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