Lightning is frightening



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In the United States, an average of 73 people are killed each year by lightning. That's more than the annual number of people killed by tornadoes or hurricanes. Do you know about lightning?




By Michael R. Helfert, South Carolina Department of Natural Resources, Water Resources Division

Although lightning by strict definition is the flashing of light produced by a discharge of atmospheric electricity from one cloud to another or between a cloud and the earth, lightning to most people, and in this publication, is the electrical discharge itself. Actually, lightning is a massive spark of electricity created inside a thunderstorm. The thunder is the booming or rumbling sound that accompanies the lightning flash. Lightning may travel from different parts of the cloud or from the cloud to the ground. When lightning hits the ground, it tends to strike tall, isolated objects such as buildings and trees, because it is seeking the shortest distance to ground. The lightning flash carries an electrical charge estimated to be up to 100 million volts or more a million times greater than the electrical charge running through the electrical wiring of your home. According to Kahl (1993), lightning heats the air as it moves through it to more than 54,000 degrees Fahrenheit--five times hotter than the surface of the Sun.

Electrical charges are generated inside a cumulonimbus cloud by the updrafts and downdrafts, which carry water and ice crystals through the cloud. It is believed that the collision or interaction of water droplets with ice crystals permit electrons to jump from one atom to another. During this process the lighter ice crystals lose electrons and become positively charged. Being lighter, they tend to move to the upper part of the cloud, giving it a predominately positive charge. Warmer, heavier objects--such as raindrops and hailstones--gain electrons during these collisions and tend to settle to the lower part of the cloud, giving it a mostly negative charge with scattered areas of positive charge. As the negative charges increase within the lower part of the cloud, the ground below becomes positively charged. In a similar manner, any positive charged areas near the bottom of the cloud attract a negative charge on the surface of the earth underneath the cloud.

Which way does lightning travel? A cloud-to-cloud lightning strike begins as an invisible channel of negatively-charged air moving toward a positively-charged area. In cloud-to-ground lightning, the negatively-charged channel streams from the vase of the cloud toward the ground in a series of steps, called a stepped leader. When the stepped leader approaches the earth, a positively-charged channel, called an upward streamer, moves upward to meet it. Once these opposite electrical charges meet, a powerful surge of electricity flows through the entire channel between the cloud and the ground, creating the bright flash and roaring thunder, known as the lightning strike.

It is generally agreed that lightning strikes may be of four types: (a) Negative cloud charge to positive ground charge, (b) Positive cloud charge to negative ground charge, (c) Positive ground charge to negative cloud charge, and (d) Negative ground charge to positive cloud charge. Both negative cloud-to-ground lightning and positive ground-to-cloud lightning connect negative regions in the lower or middle cloud regions with the ground. Other types, positive cloud-to-ground and negative ground-to-cloud, link the top of the cloud and the ground.



By Richard Kithil, President, National Lightning Safety Institute

Atmospheric Physics 101. At any one time around the planet, there are 2000 thunderstorms and 100 lightning strikes to earth per second. The frequency of lightning increases in the lower latitudes (closer to the equator), and in the higher altitudes (mountainous terrain). In the USA, central Florida experiences some 10-15 lightning strikes per sq. km./yr. The Rocky Mountain west has about two thirds this activity. Central Africa, parts of Southeast Asia, and the Latin American mountain regions can experience two to three times as much lightning as central Florida.

Lightning leaders from thunderclouds proceed in steps of tens of meters, electrifying ground-based objects as they approach the earth. Ground-based objects may launch lightning streamers to meet these leaders. Streamers may be heard (some say they "sound like bacon frying") and seen (we may notice our hair standing on end). A connecting leader-streamer results in a closed circuit cloud-to-ground lightning flash. Thunder accompanying it is the acoustic shock wave from the electrical discharge. Thus, thunder and lightning are associated with one another.

Flash/Bang. We all possess a first-class lightning detection device, built into our heads as standard equipment. By referencing the time in seconds from seeing the lightning (the FLASH, or "F" ) to hearing the accompanying thunder (the BANG, or "B"), we can range lightning's distance. A "F" to "B" of five seconds equals lightning distance being one mile away. A "F" to "B" of ten = two miles; a "F" to "B" of twenty = four miles; a "F" to "B" of thirty = six miles; etc.

(Editor's note. Geez, this isn't rocket science. The lightning is one mile away for every 5 seconds between seeing it and hearing it.)

New information shows successive, sequential lightning strikes (distances from Strike 1 to Strike 2 to Strike 3) can be some 6-8 miles apart. Taking immediate defensive actions is recommended when lightning is indicated within 6-8 miles. The next strike could be close enough to be an immediate and severe threat.

Lightning is a capricious and random event. It cannot be predicted with any accuracy. It cannot be prevented. Advanced planning in the form of a risk management program is the best defense for maximum safety.

Standard lightning defenses. The eco-tourism environment is different from situations where substantial buildings or fully enclosed metal vehicles are the recommended shelters. Lightning in remote terrain creates dangerous conditions. Follow these guidelines:


LIGHTNING SAFETY TIPS.

AVOID: Avoid water. Avoid all metallic objects. Avoid the high ground. Avoid solitary tall trees. Avoid close contact with others - spread out 15-20 ft. apart. Avoid contact with dissimilar objects (water & land; boat & land; rock & ground; tree & ground). Avoid open spaces.

SEEK: Seek clumps of shrubs or trees of uniform height. Seek ditches, trenches or the low ground. Seek a low, crouching position with feet together with hands on ears to minimize acoujstic shock from thunder.

KEEP: Keep a high level of safety awareness for thirty minutes after the last observed lightning or thunder.

Medical treatment and symptoms. Treat the apparently dead first. Immediately administer CPR to restore breathing. Eighty percent of lightning strike victims survive the shock. Lightning strike victims do not retain an electric charge and are safe to handle. Common lightning after effects include impaired eyesight and loss of hearing. Electrical burns should be treated as other burns.

Did you learn something about lightning? Take the Red Cross Lightning Quiz.

By Michael R. Helfert, South Carolina Department of Natural Resources, Water Resources Division

Virginia Deaths and Injuries

Lightning is an underrated killer in Virginia. During the period 1959-1993, 45 people have been killed by lightning, 178 people injured (see Table 7-1), with property losses in the millions. The random nature of lightning-caused deaths, plus the fact that lightning is such a common event in Virginia, often results in little publicity given to lightning casualties.

Although lightning is a year-round event, all of Virginia's casualties since 1959 occurred during the warmer part of the year, March through October. There has been considerable variation from year-to-year in the number of people reported struck by lightning, varying from none in the years 1959, 1960, 1962, 1964, 1973, 1976, and 1984, to 39 people injured by lightning in 1989. The largest number of fatalities in a single year were four in 1961 and again in 1985.

There is a positive relationship between the number of thunderstorms and lightning strikes. Although it is difficult to explain the variability in the annual number of lightning fatalities, there were slightly more (58%) during the first half of the period than during the last half (42%). Hopefully, increased awareness of the lightning hazard has led to this decrease.

The total deaths and injuries by month caused by lightning during the 1959-1993 period are itemized below:
Month Deaths Injuries
Jan 0 0
Feb 0 0
Mar 0 1
Apr 0 4
May 10 10
Jun 10 21
Jul 11 95
Aug 11 39
Sep 3 8
Oct 0 0
Nov 0 0
Dec 0 0
TOTAL 45 178

Listed below is a summary of some of the known activities or locations of people injured by lightning in Virginia, 1959-1993. Unfortunately, in 57% of the cases, the activity of the person is not known:

LOCATION OF PERSON NUMBER OF PERCENT OF TOTAL
WHEN INJURED INJURIES PEOPLE INJURED

Open fields, or open 17 10%
spaces

Under or near trees 39 22%

Boating or water 8 4%
related

On or near tractors 2 1%
or heavy equipment

On golf courses 7 4%

At or using telephone 4 2%

Either other activities 101 57%
or unknown

These Virginia lightning statistics vividly illustrate the danger of being either under or near trees during a thunderstorm. During the period of record, 1953-93, 22% of the people injured were either under or near trees. As an example, in August 1993 four people attending a funeral were standing near a tree when lightning struck. They were seriously injured but fortunately survived. Another dangerous location during a thunderstorm was an open area. Twenty percent of Virginia's lightning fatalities occurred when the victims were in the open when struck.

Being near a window proved to be unsafe location during a thunderstorm. There were a number of instances where someone was injured or killed while standing near a window looking outside. For example, in August of 1993 two women in separate homes during a thunderstorm were injured while looking out the window.

The largest number of known injuries during a single thunderstorm was in 1989 when 30 people attending a fair were injured by a lightning strike. While everyone survived, three of the victims were seriously injured.


VIRGINIA LIGHTNING STATISTICS
(Table 7-1)


YEAR INJURIES FATALITIES
59 0 0
60 0 0
61 11 4
62 0 1
63 1 1
64 0 1
65 9 3
66 1 3
67 2 1
68 1 1
69 6 2
70 1 0
71 5 3
72 4 2
73 0 1
74 1 0
75 22 1
76 0 0
77 1 1
78 2 3
79 1 0
80 6 2
81 2 1
82 6 0
83 3 0
84 0 0
85 6 4
86 10 1
87 7 2
88 4 2
89 39 0
90 7 1
91 9 1
92 1 0
93 10 1
TOTAL 178 45


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