Struck by Lightning - tbp.org and physics of lightning strikes. ... ership the odds of a house being struck by lightning exceed ... improved building codes for lightning protection,
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WINTER 2005 T H E B E N T O F T A U B E T A P I 15
phone was cooked. Throughout the house, several electricfans, nightlights, and dimmer switches were stone dead.Outdoors, the automatic garage door had frozen a foot abovethe concrete floor and no longer responded to the hard-
wired button from the kitchen or the radio-acti-vated remote controls. Most tellingly, on the roofdirectly above my office and bedroom, the taper-ing concrete upper part of the chimney had beensheared in two, and concrete chunks lay aroundmy driveway.
Lightning had struck my house.As curious neighbors paraded through to see
what lightning damage looked like, followed by in-surance adjustors and workmen giving estimates,it seemed everyone either had a personal lightning-damage story or directly knew someone with astory. One had a computer zapped when lightningstruck several houses away. Another had nearlybeen struck as a teenager playing ball during a
BANG! BANG!A quarter to three on the morning of August 26, 2003, in themidst of an unusually violent thunderstorm that had my 12-year-old daughter Roxana quivering against me, came twofast blinding flashes and simultaneously two fast, deafeningcracks like a rapid pair of cosmically loud pistol shots. MyGod, that was close! I exclaimed, watching the nightlightacross the second-floor bedroom flicker, fade, and die. Justhow close was it?
When I walked downstairs at dawn as usual to check myemail, my freelance writers office looked as though a smallbomb had exploded in the fireplace. Its brass frame had beenblasted out of its three-inch masonry bolts and one of itsglass doors launched 10 feet away. The foot-wide inch-thickmarble slabs on the sides of the fireplace had been blownout to a 45 degree angle, one of them split in half [Fig. 1]. Sootand gray plaster/brick/concrete grit coated carpet, curtains,computer, desk, papers, books, and vertical files, and a burntsmell permeated the large room. Fortunately for me, thecomputer booted normallypraise be to its battery-backupuninterruptible power supply/surge protector (UPS)butthe UPS itself had taken a hit through the phone line, be-cause the computers modem could not get a dial tonethrough its jack. My color inkjet printer/scanner/photocopierwas totally dead; my black-and-white laser printer wouldturn on, but not respond to print commands.
Nor was the damage limited to my office. In the kitchen,my microwave oven was fried. Upstairs, the cordless tele-
Figure 1 Lightning struck the authors chimney on August 26, 2003,shearing the masonry holding the metal damper (upper left), and blasting
a fireplace into a first-floor office (lowerright). The strike also fried the automaticgarage-door opener mechanism (lower left)and appliances throughout the house.
A powerful electrical storm created an eerie tapestry of light in thehours preceding the launch of STS-8, August 31, 1983 at KennedySpace Center.
Struck by Lightningby Trudy E. Bell
If you think your odds of winning the lottery are about the same as getting
16 WINTER 2005 T H E B E N T O F TA U B E TA P I
thunderstorm in a half-flooded field. A third felt his haircurl over his entire body just before a bolt cleaved a treeoutside the window, not 10 feet away. The chimney brick-layer himself was working simultaneously on another house15 miles east of mine that had been struck in the same stormthat had struck mine. A month after my experience,Clevelands Plain Dealer ran an essay by a local womanshaken by the experience of seeing her living room wallpunctured by a lightning bolt that entered and explodedher television set without disturbing anything else.
Advice came fast and contradictory. Should I put uplightning rods? I asked the electrician. Immediately heshook his head and responded: Absolutely not! Lightningrods actually attract lightning! And no one could answermy basic question: Why did the lightning strike my houseinstead of any of the much taller trees nearby? The bestanswer was harrumphed by one insurance adjustor whodseen it all: Lightning does what it wants to do. Theres noaccounting.
If you live through it, write about itthats myjournalists motto. And since no one seemed to have straightanswersat least not ones satisfying to someone with sci-entific curiosityit was clear there must be a story in thefrequency and physics of lightning strikes.
WHAT ARE THE ODDS?The single most astonishing fact is just how often lightningstrikes the earth. Numbers vary widely with the source,but the order of magnitude is clear: ever since the NationalLightning Detection Network across the continental UnitedStates was installed in 1989 by Global Atmosphericsnowthe worldwide Vaisala Group, headquartered in Finland
something like 20 to 25 million cloud-to-ground flashes aredetected annually over the nation. Because about half oflightning bolts are forked, that means lightning strikes morethan 30 million points in the U.S. each year. That trans-lates into a nationwide annual average of some four strikesper square kilometer or 10 per square mile. True, arid desertareas suffer fewer strikes, but subtropical Florida is theall-American capital, annually averaging 10 strikes persquare kilometer or more than 25 per square mile [Fig. 2].Nationwide, the prime lightning season extends from Maythrough September, although lightning has been known tooccur in winter snowstorms. Worldwide, Central Africa,parts of Southeast Asia, and mountain regions of LatinAmerica attract double or triple the amount of lightning ascentral Florida [Fig. 3].
You and Roxana are unbelievably lucky that youwerent hurt or killed and that your house wasnt set onfire! exclaimed a friend upon hearing my account. Werewe ever. My house has two chimneys; the one the lightningstruck runs down the wall at the head of my bed, becausemy bedroom is directly above my office.
National Weather Service statistics kept for more thanhalf a century reveal that on an annual average more peopleare killed by lightning than by tornadoes, floods, or hurri-canes [Table 1]. (The single largest category of victims isgolfers, because they are often the tallest beings in wide,flat terrain or they huddle for shelter under lone trees thatmay draw lightning; golfers alone account for more thansix percent of victims.) But fatalities comprise only 10 per-cent of people actually struck by lightning. About 1,000 ayear across the United States live through the experiencebut suffer burns, cataracts, or more debilitating neurologi-cal injuries; one common injury is hearing loss from theacoustic shock of accompanying thunder, which can reach apressure of 10 atmospheresenough to burst eardrums.
The top of alarge thunder-storm, roughly20 km across, isilluminated by afull moon andfrequent burstsof lightning.These twoimages weretaken nineseconds apartas the STS-97Space Shuttleflew overequatorialAfrica east ofLake Volta onDecember 11,2000. Becausethe shuttletraveled atseven km/sec,the astronautsperspective on this storm system became more oblique over theinterval between photographs. The images were taken with a Nikon35mm camera equipped with a 400mm lens and high-speed (800 ISO)color negative film.
rank1 - 1011 - 2021 - 3031- 52
flashes/sq. km/yr 8 - 16 2 - 4.5 - 1.25 - .5
Figure 2Approximately 22million lightningflashes occur overthe U.S. per year,amounting to about30 million cloud-to-ground strikesbecause half oflightning is forked.Most lightning occursover the midwesternand southeasternstates, with Floridathe nations lightningcapital, averagingmore than 25 strikesper square mile peryearthree times thenational averageaswell as a dispropor-tionate one-sixth ofthe nations lightningfatalities.
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INSURING THE RISKFar more common than deaths or injuries from lightning isproperty damage. According to Richard Kithil, founder andCEO of the National Lightning Safety Institute, Louisville,CO, about one house in 200 is struck per year. As nearly asI can calculate, that means that over a lifetime of home own-ership the odds of a house being struck by lightning exceedthe lifetime odds of a womans getting breast cancer. Ac-cording to various insurance sources, lightning damageamounts to nearly five percent of all paid insurance claimsnationwide each year, with residential claims alone exceed-ing a billion dollars. The average residential payout perlightning claim exceeds $5,000. Mine topped $16,000, whichincluded rebuilding the chimney and fireplace and replac-ing both circuit-breaker boxes plus every switch and socketin the housethis latter a routine fire-prevention precau-tion after a lightning strike, especially one documented tohave traveled through the wiring of the entire house, be-cause you cant guarantee that the breakers will functionin the future, explained the electrician. Good precaution:he later found charring in several sockets and switches notconnected to appliances that failed.
Figure 3 Data from space-based opticalsensors (April 1995 to November 2000)reveal the uneven distribution ofworldwide lightning strikes, with colorvariations indicating the average annualnumber of lightning flashes per squarekilometer. Central Africa is the lightningcapital of the world.
Commercial costs are even greater, even not countingindirect costs (such as payroll for a workforce idled by notbeing able to use the premises). According to the electricutility companies research group EPRI, lightning accountsfor 30 percent of all power outages, and losses to the indus-try exceed $1 billion annually.
Because a lightning bolt can reach temperatures exceed-ing 30,000Cfive times hotter than the surface of t