Received: from hplms26.hpl.hp.com by opus.hpl.hp.com with SMTP (1.37.109.8/15.5+ECS 3.3+HPL1.1) id AA14145; Thu, 24 Aug 1995 22:54:31 -0700 Return-Path: <kasplash@crl.com-DeleteThis> Received: from mail.crl.com by hplms26.hpl.hp.com with SMTP ($Revision: 1.36.108.11 $/15.5+ECS 3.3+HPL1.1S) id AA210500138; Thu, 24 Aug 1995 22:55:38 -0700 Received: from crl10.crl.com by mail.crl.com with SMTP id AA28888 (5.65c/IDA-1.5 for <wind_talk@opus.hpl.hp.com-DeleteThis>); Thu, 24 Aug 1995 22:47:40 -0700 Received: by crl10.crl.com id AA14621 (5.65c/IDA-1.5 for wind_talk@opus.hpl.hp.com-DeleteThis); Thu, 24 Aug 1995 22:47:40 -0700 Date: Thu, 24 Aug 1995 22:47:39 -0700 (PDT) From: Bob Galvan <kasplash@crl.com-DeleteThis> To: wind_talk@opus.hpl.hp.com-DeleteThis Cc: Multiple recipients of list <wind_talk@opus.hpl.hp.com-DeleteThis> Subject: Re: WIND_TALK digest 63 In-Reply-To: <9508242049.AA21572@jr.hpl.hp.com-DeleteThis> Message-Id: <Pine.SUN.3.91.950824222534.14227A-100000@crl10.crl.com-DeleteThis> Content-Type: TEXT/PLAIN; charset=US-ASCII
Jim Paugh asks:
"What I would like to hear is an explanation of why slack current occurs
after say, a low tide. For instance, today, low tide at Crissy is at
5:03pm, but low slack is at 7:29pm! How is it that slack current occurs
2.5 hours after low tide? "
Bottom Bob replies:
Think of the tides as very long period waves. This tidal wave emanates
from a node somewhere between Mexico and Hawaii and travels northward toward
us. The trough is 6 hours behind the crest.
When this wave crest gets to the Golden Gate, it enters and rolls right
on past Alcatraz, down to the South Bay, up to the North Bay and beyond,
past Vallejo, Antioch, Sherman Island, Windy Cove and on to Sacramento.
It takes about five hours to get to Rio after passing the Golden Gate.
So as this wave crest rolls up river, water continues to FLOW into the
bay/delta system even as the water LEVEL drops at the Gate. The
flowing water is making the level rise futher up the bay.
Conversely, consider low water at the Gate. Low water at San Rafael is
an hour later, and low water at Rio is five hours later. So even as the
tide rises at Crissy, water continues to drain out of the upper bay for
another 1.5 to 2.5 hours.
Bob Galvan
kasplash@crl.com-DeleteThis
P.S. Going to Maui on Saturday.
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