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 AA19767; Tue, 13 Dec 1994 17:29:29 -0800 Return-Path: <jluu@mainsoft.com-DeleteThis> Received: from ftp.mainsoft.com by hplms26.hpl.hp.com with SMTP (1.36.108.4/15.5+ECS 3.3+HPL1.1S) id AA00017; Tue, 13 Dec 1994 17:29:35 -0800 Received: from mainsoft.mainsoft.com ([192.187.191.210]) by firewall.mainsoft.com (4.1/SMI-4.1) id AA01156; Tue, 13 Dec 94 17:21:47 PST Received: from bamako.mainsoft.com by mainsoft.mainsoft.com (4.1/SMI-4.1) id AA10763; Tue, 13 Dec 94 17:32:26 PST Date: Tue, 13 Dec 94 17:32:26 PST From: jluu@mainsoft.com-DeleteThis (Jose Luu) Message-Id: <9412140132.AA10763@mainsoft.mainsoft.com-DeleteThis> To: wind_talk@opus.hpl.hp.com-DeleteThis Subject: Re: Tide Data and high/slack time differences
> On a related note, does anyone know why high/low tide times differ
> (sometimes substantially) from slack times?
Think about the golden gate, there is a time where the tide is high
and the bay has not filled up yet because of the restriction (strait).
Then the tide begins to go down and the bay continues to fill up, at
some point later, the bay has filled up enough, and the tide has gone
down enough for the current to stop flowing, this is the slack.
For those used to electronics, it is like the phase lag between current
and voltage in an RC circuit.
Obviously the phase lag depends on R (the flow restriction), and C
(the water capacity downstream), this means that the time difference
between high and slack differs among locations.
I noticed and happened to think about all this when I was sailing at PA.
The road goes over a little bridge which is in fact more a burried pipe
than a bridge (high restriction). This pipe communicates between the harbor
and some channels in the baylands. I have always been amazed by the phase
difference there (pipe flowing full at high tide).
I hope this is clear enough.
Jose
This archive was generated by hypermail 2b29 : Mon Dec 10 2001 - 02:28:27 PST