Dear Tom,
During the Oct. 2 storm, I noticed lightning bolts going across the sky horizontally. Were they striking the ground out of my sight or can lightning occur without striking the ground?
Tim Rasmussen, Winfield
Dear Tim,
Most lightning bolts are not ground strikes. Of the approximately 100 million flashes that occur annually in the skies above the United States, only about one in four is a ground strike.
The horizontal extent of some lightning bolts is so great that the flash you see streaking overhead might actually be part of a bolt that is making ground contact beyond your line of sight.
Lightning expert Ron Holle tells us that a lightning detection system operated by the Vaisala Group has measured “quite a few flashes over 100 miles in length, and the current record is 120 miles.”
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
