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» Online Classroom   »   » Public Discussion of Marine Weather   » When can sailing against 3 or 4 kts of current be to your advantage?

   
Author Topic: When can sailing against 3 or 4 kts of current be to your advantage?
David Burch


 - posted May 06, 2006 01:31 PM      Profile for David Burch           Edit/Delete Post 
Answer: when the wind is flowing with the current at 30+ kts!

An example from our recent training cruise was Apr 27 at about 5 pm ADT sailing south toward Exchange Cove off of Snow Pass, AK in a sustained 30 kts of south wind, and into a north flowing current of some 3+ kts, judging by SOG and predicted currents at the time. Waves were still breaking over the bow but the situation would have been much worse in slack water, since the current flowing with the wind flattened out the seas to a large extent.

Three or four hours later when the current reversed to flow into that wind it would have been quite horrible... 30 kts of wind against almost 4 kts of current would cause tremendously steep waves.

In the online weather course we will analyze this situation using theoretical steepness factors. We have graphs of these factors in the weather trainer program. They depend on the ratio of current speed to wave speed which we can estimate from the wind speed and duration.

From: Starpath, Seattle, WA


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