Lightning strike leaves its mark

Dax Williams, 13, of Mullins Mill Road holds a strip of bark forced off a tree in his front yard when lightning struck and split its trunk. (T-G Photo by Clint Confehr) [Click to enlarge]

A bolt of lightning stripped the bark off a front yard tree at a Shelbyville family's home Wednesday afternoon and made more noise than thunder, but what a clap that was.

"It sounded like a bomb going off in the house," Bo Williams of Mullins Mill Road said. "It lit the whole house up with a bright light, set the alarm off with sirens and the alarm company called."

Controls for Williams' swimming pool were "knocked out," he said of the system that's grounded so swimmers have some protection from being electrocuted by nearby lightning strikes.

Nobody was hurt, but cable TV service was interrupted on a street that got service just last year.

The question arose as Williams recalled a lesson from one of his former teachers, Deery Eakin, who taught him that lightning strikes upward from the ground.

"It's almost philosophical that it's the strike that's going back" into the clouds, said Sam Herron, a National Weather Service meteorologist who explained lightning last night for the Times-Gazette.

Bo Williams of Mullins Mill Road speaks with a technician from Charter Communications cable TV service who declined to give his name. The charge removed bark from the tree and blew dirt from the ground above a root that connected the trunk and the cable TV service line buried a few inches below the lawn's surface. (T-G Photo by Clint Confehr) [Click to enlarge]

Traveling at the speed of light, lightning goes in three directions: between clouds, from clouds to the ground, and back.

"It starts by a separation of static charges from the ice crystals in the clouds and the water droplets in clouds," Herron began.

Static electricity builds up in a way similar to slippers on a wool carpet.

"Separation comes from the turbulent motion from up-drafts of rising winds as the lower part has the liquid and the top area has ice crystals," Herron said. "The particles stir around and generate charges. When they're released, you get lightning.

"But it's not just a bolt that comes down and goes 'zap,'" he said. "The ground has a charge that's different from the charge in the clouds and the charges build up and when there's an opportunity to restore balance in the atmosphere, it results in lightning."

Small flashes reach down, rapidly, and when they reach an avenue for return.

That return could be from a tree, like the one Williams must have removed because the trunk is split.

"When the connection is made, there's a return bolt and that's the big flash, but since it's all so fast, I wouldn't differentiate that it's a return strike," Herron said. "It's so fast that it's all together.

And it causes a huge expansion of air that's heated by the lightning and that expansion of air is the thunderous shockwave.

For more on lightning, read the Weather Service's web site at www.weather.gov/nashville and follow the "education" link.

Williams' computer colors were jumbled for a while, but they came back, he said.

As for lightning striking twice in the same place. It won't at that part of Williams' yard after the tree's taken down.