- The Washington Times - Wednesday, August 2, 2006

When lightning strikes, the danger is not in using a cell phone, IPod or other electronic device, but in being outside, says Gregory Forbes, severe-weather expert for the Weather Channel in Atlanta.

“The cell phone is irrelevant. Being outside is the problem,” Mr. Forbes says. “You need to be indoors, away from the lightning path.”

According to the Lightning Safety Group’s 30-30 rule, if thunder is heard within 30 seconds of a lightning flash or bolt, people should move indoors or into a metal-topped vehicle, which serves as a conductor, and stay there for 30 minutes after the last thunder is heard, Mr. Forbes says. (The Lighting Safety Group was formed during a 1998 meeting of the American Meteorological Society in Boston as an ad hoc group to develop safety advice.)

“Basically, anytime you hear thunder, there’s some danger,” he says.

Mr. Forbes and other meteorologists working for weather-related services provide advice on how to avoid being struck by lightning.

“The general guideline is, anytime a thunderstorm is nearby or the sky looks threatening, get inside,” says John Jensenius, warning coordination meteorologist for the National Weather Service in Gray, Maine.

Lightning is a spark of electricity within the atmosphere or between a cloud and the ground that results from a buildup of charges on ice crystals, water droplets, hail and other particles within the cloud, Mr. Jensenius says.

The ice crystals are lifted by the updraft, or rising air, of the storm to the top of the cloud, while the heavier pieces of hail remain in the middle or fall to the bottom of the cloud, Mr. Jensenius says. In the process, the ice crystals take on a positive charge and the hail a negative charge as they collide with one another, he says.

“The negative charges in the cloud cause positive charges to build up on the ground,” Mr. Jensenius says. “That positive charge follows that cloud around almost like a shadow.”

A negatively charged, 1-inch-wide channel called a stepped leader forms in the negatively charged portion of the cloud and moves toward the ground, Mr. Jensenius says. At about 50 to 100 yards from the ground, a positive charge reaches up to meet the stepped leader, establishing a channel, he says.

“The negative charge comes to the ground as the channel becomes positively charged,” he says. “Electricity passes through, and you get a visible flash of lightning.”

The lightning flash moves at about 200 million miles per hour and heats the air for a fraction of a second to about 50,000 degrees Fahrenheit, or five times the temperature of the sun, Mr. Jensenius says. As the air is heated and expands outward, a shock wave results, creating thunder that can be heard up to 10 miles away, the striking range of lightning, he says.

“Lightning isn’t always caused by thunderstorms,” says Doug Hill, chief meteorologist for WJLA/ABC 7 in Arlington and a forecaster for WTOP radio in Northwest. Lightning can occur during fires and near volcanoes, he adds.

“Lightning is a discharge of electricity. … When the charges build up, they have to be released,” he says.

Lightning tries to reach the closest point as it travels toward the ground and will hit the tallest object in its path, says Gregory Jenkins, associate professor and director of the graduate program in atmospheric sciences at Howard University in Northwest. He holds a doctorate in atmospheric sciences.

A person in an open field or flat, open area can become that object, Mr. Jenkins says.

Other dangers are inside the home.

For instance, electrical devices plugged into an outlet, such as a telephone or computer, or that are hard-wired outside, can serve as conductors and the wiring as a conductive path, Mr. Jensenius says.

“If your house is struck or lightning strikes nearby, it can follow the wires and affect anything nearby, including you,” he says.

Mr. Forbes recommends staying away from plumbing, such as a shower or a sink, because charges can be conducted along the pipes, he says.

The charges also can be conducted along the electrical and plumbing lines for indoor and outdoor swimming pools, Mr. Jensenius says.

Being on water, which, in its pure form, is a poor conductor of electricity, presents another danger because the person or boat on the water becomes the tallest object, Mr. Forbes says. Water in a lake or pond can have a variety of materials in it, and with enough voltage can conduct electricity, he says.

“Historically, in a typical year, lightning will kill more people than tornadoes or hurricanes,” Mr. Jensenius says.

An average of 66 people are killed in the United States each year from lightning, Mr. Jensenius says. The number of cloud-to-ground lightning strikes in the United States averages 25 million a year, he says.

“We estimate nine of 10 people survive a lightning strike,” Mr. Jensenius says. “Primarily, it’s cardiac arrest that kills people. It doesn’t mean they’re without problems, because electricity going through the body can do neurological damage.”

Having a cell phone or other metal object, such as jewelry, next to the body can leave a burn mark from a lightning strike, Mr. Jensenius says.

“That’s insignificant compared to the neurological effects lightning can cause,” he says.

Survivors of lightning often receive a glancing blow or a portion of a lightning strike, which can carry 15,000 to 200,000 amps of current, 1,000 times more than household amperage, Mr. Forbes says. The lightning may strike the ground or an object first before hitting a person, he says.

“It’s rare to be struck, and more so to be struck more than once,” Mr. Forbes says.

If people are struck more than once, it is a matter of coincidence or of engaging in activities that put them at risk, such as being outdoors during a storm, Mr. Forbes says.

People can experience warning signs when lightning is imminent, such as a tingling sensation, their hair standing on end and a funny smell in the air, Mr. Jensenius says.

“You don’t want to wait for those to occur,” he says. “It’s best if you hear thunder to get inside immediately.”

Why wait 30 minutes once inside?

“Often charges linger in the atmosphere. You can get lightning well after the rain ended,” Mr. Jensenius says.

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