Skinny lightning bolts
Q: My kids were wondering how wide and long lighting can
be. George, Greeley, Colorado
 Lightning pencil thin and up to a hundred miles long.
Photo courtesy of Alan Moller, NOAA/National Weather Service.
A: The return stroke of a lightning bolt the bright light we
see follows a charge channel only about a half-inch (1.3-cm) wide. As deadly
as lightning is, as brilliant as it is the channel is no wider than a pencil.
A luminous corona (made of hot ionized gases) envelops the
lightning channel. This faint glow may be 10 to 20 feet (3 to 6 m) across.
How long? A poker-thin bolt can extend, like a deadly tongue,
118 miles or more. The longest lightning bolts start at the front of a squall
line and go backwards horizontally to the trailing cloud layers. "Lightning can
be as little as a few feet long to many miles long," says
David Schultz, meteorologist at the National
Severe Storms Laboratory in Norman, Oklahoma. The longest recorded bolt was near
Dallas, Texas 118 miles (190 km) long.
Most lightning bolts are about a mile (1.6 km) long.
By the way, we can hear thunder about 10 to 15 miles (16 to 24
km) from a thunderstorm.
How to tell how far? When you see a lightning flash, start
counting the seconds until you hear the thunder. Say, you get to10 seconds. Take
that number and divide by 5 to get the distance in miles: in this case, 2 miles
(3 km).
This example is an unsafe distance. According to the National
Severe Storms Laboratory, go inside if the count is less than 30 (15 miles, 24
km). Also, stay inside for 30 minutes after you see the last lightning bolt or
hear its thunder. These rules may seem stringent but lightning is a tricky,
devious phenomenon.
Further Reading:
National Severe Storms Laboratory: Questions and answers about
lightning
USA Today: Anatomy of a lightning strike neat graphic
(briefly, turn off your firewall to see it)
(Answered Oct. 1, 2004, Updated July 22, 2007)
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