Dear Tom,
Why does lightning appear to be forked or zigzagged?
Connie VanSwol
Dear Connie,
It’s a vexing question, and even lightning experts cannot give a definitive answer. Lightning researcher Ron Holle at the National Severe Storms Laboratory in Norman, Okla., says lightning comes to the ground in “steps” approximately 50 yards in length. A precise explanation for this is not known, except that it seems to be the result of the composition of the Earth’s atmosphere.
Holle further explains that as a cloud-to-ground lightning flash comes down, it generally reaches toward the ground within 18 degrees of the vertical. Its lower tip branches out, unsuccessfully spreading in different directions, as revealed in lightning photographs of downward-pointing branches that end without reaching the ground. The best path—and the path that ultimately reaches the ground—is most likely connecting to slightly more favorable pockets of electric charges attached to water and ice particles in the air.
———-
Tom Skilling is chief meteorologist at WGN-TV. His weather forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.
Send your questions to:
ASK TOM WHY, 2501 Bradley Place, Chicago, IL 60618
e-mail: asktomwhy@tribune.com
