Dear Tom,
I’ve been sailboat racing on Lake Michigan for years. I’m always interested in gathering the most accurate wind information possible. With the newest GPS units, I can get NEXRAD information right on the boat. Just how good is the data?
Tom Gorey
Dear Tom,
Sorry to say, the doppler radar wind information is not of much use to sailors on Lake Michigan. For one thing, the radar antenna is aimed 1/2 degree above the horizon. Due to the curvature of the Earth, that beam is measuring the atmosphere almost 2,000 feet above the lake–and even higher father from the radar. Additionally, the radar needs a target to measure–clear skies won’t do. So if you’re seeing radar returns, the weather could be getting worse. Finally, the radar only measures the component of the wind moving toward or away from the radar. Any winds perpendicular to the radar beam are reported as zero.
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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 meteorologist Dennis Haller contributed to this page.
