LIGHTNING by gdf57j


T h e U n d e r r a t e d K i l l e r

The Striking Facts:
It is estimated that at any given moment nearly      Lightning usually kills more people each year than do
2,000 thunderstorms are in progress over the         tornadoes and hurricanes combined. Occasionally, flash
earth’s surface, and lightning strikes the earth     floods will kill more people. Lightning fatalities are not
100 times each second. There are about 45,000        publicized as often as hurricane and tornado deaths. Lightning
thunderstorms daily and 16 million annually          deaths usually happen one or two at a time while several may
around the world. There are at least 100,000         be killed during a tornado or hurricane event.
thunderstorms annually across the United
States. Since 1940, lightning has killed close       The first strike of lightning from a thunderstorm may be
to 9,000 people. Since 1959, Florida has had         the most dangerous, not in terms of impact, but
more lightning deaths than any other state.          because of the element of surprise. In Santa
In a ten year period, approximately 75 deaths        Rosa County, three men were standing
were reported in Florida from lightning, June,       under a tree with a dark storm cloud
July and August are by far the highest casualty      in the distance. The first strike from
months with an average of 17 deaths occurring.       the distant storm hit the tree and
                                                     eventually killed all three. A boy
Northwest Florida averages 75 thunderstorms a        swimming near Fort Pickens
year. The west central part of the state leads the   was struck by lightning from a
country in frequency of thunderstorm days each       storm that was occurring over
year with more than 100.                             the mainland. Luckily, he lived
                                                     but was severely injured. In Bay
                                                     County, a family outing turned
                                                     into a disaster when two boats were
                                                     trying to get to shore ahead of an
                                                     approaching thunderstorm. Lightning
                                                     struck the boats killing two people.

                                                     The graph below (left) shows the months
                                                     most prevalent for lightning fatalities.

                                                     The Florida map below (right) shows the distribution of
                                                     lightning fatalities by county.
What Causes Lightning?
There are different kinds of lightning: within clouds, between     How Thunderstorms Develop:
clouds, and from clouds to clear air. The lightning that           As thunderstorms develop, interactions
concerns people most goes from cloud to the ground, as             of charged particles produce an intense
seen in the pictures above. These flashes start fires, splinter    electrical field within a cloud. A large
trees, knock out electric power and even kill people. Cloud        positive charge is usually concentrated
to ground lightning represents only about 20 percent of all        in the frozen upper layers of the cloud;
  lightning strikes.                                               a large negative charge, along with a
                                                                   smaller positive area, is found in the lower
               Here is what happens: Negatively charged            portions.
                 electrons zigzag downward in a forked
                     pattern known as a stepped leader. As         As the thunderstorm passes over the
                       this stepped leader nears the ground,       ground, the negative charge in the base of
                         it draws a stream of positive charges     the cloud induces a positive charge on the
                           upward, usually through something       ground below and for several miles around
                            high such as a tree. As the leader     the storm. The ground charge follows the
                             and streamer come together, a         storm like an electrical shadow, growing
                             powerful electrical current begins    stronger as the negative cloud charge
                             flowing and the return stroke         increases.
                             begins with an intense wave of
                             positive charges traveling upward     The attraction between positive and
                            about 60,000 miles per second          negative charges make the positive
                           (about one-third the speed of light).   ground current flow up buildings, trees
                         This is the light that we see. The        and other elevated objects in an effort
                       process can repeat several times in         to establish a flow of current, but air – a
                     less than half a second, making lightning     poor conductor of electricity – insulates
                  flicker.                                         the cloud and ground charges, preventing
                                                                   a flow of current until huge electrical
            What Causes Thunder?                                   charges are built up. Lightning flashes
     Average lightning strikes produce currents of 30,000          when the attraction between positive and
amperes, although some may approach 100,000 amperes. The           negative charges become strong enough
rapid rise in current produces temperatures in the lightning       to overcome the air’s high resistance to
channel of more than 50,000º F which causes the air in the         electrical flow.
channel to expand. The expanding air cools, then contracts.
This rapid expansion and contraction starts air molecules
moving back and forth, making sound waves we hear as
thunder (much like the sound a paper bag makes when you
blow it up and pop it—the air expands quickly making a loud
bang). When a lightning bolt flashes through the sky, we see
it instantly. Thunder (the sound that lightning creates) takes a
few seconds to reach us.
                                                                                Sound travels a mile in about
                                                                                five seconds. Start counting
                                                                                when you see the lightning,
                                                                                if you hear the thunder in
                                                                                five seconds, the lightning is
                                                                                a mile away; in ten seconds
                                                                                the lightning is two miles
                                                                                away and so on. If you see the
                                                                                lightning and hear the thunder
                                                                                at the same time, the lightning
                                                                                is directly over head. Thunder
Staying Safe During                                                             sometimes rumbles because
Thunderstorms:                                                                  we hear it first from the flash
                                               nearest us, then from other parts of the flash farther away.
• If you’re outside, get inside a building
or inside an all metal (not a convertible)     When there is no shelter, avoid the highest objects in the
vehicle.                                       area. If only isolated trees are nearby, your best protection is
                                               to crouch in the open, keeping twice as far away from isolated
• Stay indoors and do not venture outside,     trees as the trees are high. Get out of the water, off small
unless absolutely necessary.                   boats, and off beaches. The safest place is an automobile until
                                               the storm passes. If you are caught aboard a boat, crouch
• Stay away from open doors and windows,       down in the center of the boat, away from metal hardware
fireplaces, stoves, metal pipes and plugged-   such as fishing poles. Golfers using golf clubs and wearing
in electrical devices.                         cleated shoes are particularly good lightning rods. If you
                                               happen to get caught outside and you feel your hair stand on
• Don’t use pools, hot tubs, bath tubs,        end, lightning may be about to strike you. Frequently, two or
showers, sinks or other plumbing fixtures.     three seconds before lightning strikes, your hair may stand
                                               on end. Crouch over and make yourself as small an area
• Turn off the television and avoid using      as you can. Do not lie down as the wet ground can carry the
corded telephones or computers during a        lightning.
                                               Persons struck by lightning receive a severe electrical shock
• Wait 30 minutes after the last clap of       and may be burned, but they do not carry an electrical
thunder before venturing outside.              charge and can be handled safely. A person killed by
                                               lightning can often be revived by prompt first aid medical care
      For more information contact:            (CPR, mouth to mouth).

                                               Do not become another lightning statistic. When dark
                                               clouds are around, lightning is seen or thunder is heard,
                                               get inside and stay safe.

           Escambia County
  Division of Emergency Management
         6575 North “W” Street
        Pensacola, Florida 32505

To top