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Published: Sunday, 7/29/2001

Lightning can be strikingly beautiful, or strikingly dangerous.

Lightning can be strikingly beautiful, or strikingly dangerous.

It all depends on whether you are in a safe place and can thrill at witnessing this awesome, dazzling spectacle of nature, or whether you are caught outdoors - unsheltered and vulnerable.

The air within a lightning strike can reached 50,000 degrees Fahrenheit, and lightning can heat its path five times hotter than the surface of the sun. One ground stroke can generate between 100 million and one billion volts of electricity.

Such heat and power generate great pressure waves followed by a series of compressions - we simply call it thunder. Yet make no mistake: Thunder makes the noise but lightning does the work.

The United States experiences more than 25 million cloud-to-ground lightning strikes a year, according to the National Oceanic and Atmospheric Administration. Florida, the lightning-strike leader, averages some 3,500 bolts a day. Moreover, lightning may occur at any time of year, though it is most prevalent in summer.

Nationally, about 85 people are killed every year by lightning, according to NOAA records. Death usually is attributed to cardiac arrest or stopped breathing. The fatality toll is more than that caused by tornadoes or hurricanes.

Neighboring Michigan trails only Florida, moreover, in terms of annual lightning fatalities. It averages between two and three deaths a year and 94 in the last 40 years. Michigan's dubious track record ironically may be attributed to its great reputation as an outdoor recreation state.

Only one of 10 persons injured by lightning dies, but most of the other nine suffer lifelong severe injuries, usually neurological.

Beyond the physical threat, lightning also causes property damage - some $5 billion in losses annually. In short, lightning is an act of nature that must be reckoned with.

It takes far longer to explain lightning and its causes than it does for a bolt to strike. That usually only takes a half second.

Most lightning activity takes place within the clouds themselves - in-cloud lightning, and cloud-to-cloud or sheet lightning. About one discharge in five is cloud-to-ground, and that may come as streaks and branches or forks.

Lightning originates at altitudes of 15,000 to 25,000 feet as raindrops are drawn upward and converted to ice, the NOAA says.

For reasons not generally agreed upon, a cloud-to-ground bolt originates in this zone of water and ice. A negative electrical charge moves downward in 50-yard sections called step leaders and keeps moving ground-ward in steps, producing a channel through which a charge is deposited.

Eventually the flowing negative charge reaches a connection on the ground, where positive electrical charges, called return strokes, have collected. In a blink a megavolt circuit is completed with the cloud. The flowing charge or current produces an eye-searing flash.

Heat lightning simply is lightning so distant that the eye sees the flash in the sky above the clouds but the resultant thunder cannot be heard.

Ball lightning is a strange phenomenon that most authorities agree exists, but for which no accepted theory of explanation exists. It generally is described as a luminous sphere, usually about six inches in diameter, that appears and lasts for just seconds, usually after a nearby cloud-to-ground bolt.

The “ball” may roll around erratically, bounce along the ground, or even pass through closed windows, thin metal walls, or even slip down chimneys before fizzling out. Rarely, ball lightning is said to explode.

Though there is no such thing as being absolutely safe from lightning, NOAA offers some common-sense safety tips:

  • Use the 30-30 rule around lightning. Quickly seek safe shelter if the time-lapse between a boom of thunder comes within 30 seconds of a lightning flash. Stay in safe shelter 30 minutes after hearing the last thunder.

    Thunder travels roughly at the speed of sound, a fifth of a mile a second. If lightning flashes and thunder booms five seconds later, the bolt was a mile away.

  • The most danger comes before or after the worst of a storm, not in the middle of it, because the storm's edges are taken for granted.

  • The best shelter is a substantial building with plumbing and wiring - it is grounded. Once inside, avoid using a telephone or water supplies (bathing, dishes, laundry) during a lightning storm.

    A motor vehicle with a metal roof provides good protection, more so than being in an open-sided or ungrounded building (no wiring or plumbing). The metal shell of the motor vehicle is what offers the protection - that rubber tires “insulate” the vehicle by interrupting a ground for lightning is a myth.

  • If safe shelter cannot be reached, at least avoid higher elevations or wide-open areas such as sports fields. Also avoid standing under tall objects such as trees or utility poles, and all water-related activities. Also avoid use of open vehicles, and such open-area activities as golfing.

  • In the worst case scenario, with no shelter and a strike imminent and nearby (your hair is standing on end), assume the “lightning crouch:” Put your feet together, squat down, tuck your head, and cover your ears.



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