Dear Tom,
Why do most Atlantic hurricanes occur in the August-October period?
Hope D. Arlington Heights
Dear Hope,
Tropical cyclones in the Atlantic Basin are most numerous during the late summer and early fall period because that is the time of year when the two most important ingredients needed for their formation, warm ocean water (80 degrees or higher) and weak vertical wind shear (little change in wind direction and/or speed with height) are most prevalent. Additionally, this is also the season with the highest frequency of westward moving weather disturbances in the tropics that eventually develop into hurricanes. Water, with its high specific heat, is slow to warm, and the tropical oceans in the Northern Hemisphere reach their highest water temperatures in August and early September, many weeks after the time of strongest solar insolation.
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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.)
