Dear Tom,
I heard that an El Nino may be forming due to a Kelvin wave. What is a Kelvin wave?
Martin Mockenhaupt
Buffalo Grove
Dear Martin,
In this case a Kelvin wave is a warm bump in the ocean. Forming near Indonesia, it travels east across the equatorial Pacific toward the Americas. A typical Kelvin wave is only 2-4″ high, but hundreds of miles wide with temperatures a few degrees higher than its surroundings. The waves are triggered when the easterly trades decrease. Normally, brisk trade winds push sun-warmed water west across the Pacific pooling it near Indonesia. When the trades weaken, this warm water begins a slide back to the east, due to the Earth’s rotation. When the trades decrease for just a few days or weeks, a common occurrence, the result is a Kelvin wave. However, when the event last for months or years, it usually leads to an El Nino.
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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.)
