aujax
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it's usually 20 minutes before high tide, right?
when is slack tide?
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Charlie99
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It depends upon the local geography.
Where you have a large bay with a very small entrance, it will be close to midway between high and low.
With a smaller bay / larger entrance slack will be closer to the highs and lows.
For some locations, you can get current predictions from http://tidesonline.nos.noaa.gov/
If you post the specific location you are curious about, there might be somebody that can make a recommendation --- perhaps including things like which slack is better for diving.
Where you have a large bay with a very small entrance, it will be close to midway between high and low.
With a smaller bay / larger entrance slack will be closer to the highs and lows.
For some locations, you can get current predictions from http://tidesonline.nos.noaa.gov/
If you post the specific location you are curious about, there might be somebody that can make a recommendation --- perhaps including things like which slack is better for diving.
Where?aujax:
Ok... slack tide occurs when the water level on one side of the site is the same as the water level on the other side of the site. Think for a moment about the dynamics here and you'll see why Charlie99's answer makes sense.
Rick
The good news is that most places where we want to know the tidal currents have both tide charts and tide current charts.
Ask the local divers, boaters and fishermen.
Ask the local divers, boaters and fishermen.
Don Burke
Contributor
That's a trick question.aujax:
The points where the tide is as low or as high as it is going to get are called the "stand" of the tide.
Slack water occurs when the incoming current due to the tide change cancells the outgoing current coming from the rivers and streams. Normally, this happens some time before high tide and some time after low tide. If the rains are heavy in the watershed, it may not happen at all.
Twenty minutes may be correct for the place you are thinking of. It varies quite a bit from place to place.
DivemasterJoe
Registered
You are all welcome to use my XTide server at http://64.25.141.124 to produce your own tide/current tables.
Joe
Joe
Tide tables for Idaho, Utah, Colorado, Wyoming and Montana are as follows:
Gary D.
Gary D.
DivemasterJoe
Registered
Hi All,
Right after I posted the link to my XTide server I noticed the harmonics file I was using was a little outdated. I have installed the most recent harmonics file and restarted the server.
Cheers,
Joe
Right after I posted the link to my XTide server I noticed the harmonics file I was using was a little outdated. I have installed the most recent harmonics file and restarted the server.
Cheers,
Joe
This topic has been done before and recently:
http://www.scubaboard.com/t51743.html
---
In summary slack water although its based on high/low water is NOT the same as them. Due to ocean bottom topography and land shape and many other factors slack water can be pretty much any time and incredibly hard if not impossible to predict. Local knowledge is the only reliable way.
Some sites are slack nearly all the time, some are slack relative to high AND low water, some are low water slack only and so on.
http://www.scubaboard.com/t51743.html
---
In summary slack water although its based on high/low water is NOT the same as them. Due to ocean bottom topography and land shape and many other factors slack water can be pretty much any time and incredibly hard if not impossible to predict. Local knowledge is the only reliable way.
Some sites are slack nearly all the time, some are slack relative to high AND low water, some are low water slack only and so on.
DivemasterJoe:
The UK government somehow managed to patent the harmonic constant used for the UK coastline and as a result its no longer freely available meaning no software can use it without an extortionate licence fee. The ONLY online method for it is via their own "Easytide" site and that only goes up to 6 days in advance so long term planning is out.
Not sure what date the harmonic constants on X-Tide are but they dont agree with the UKHO ones (http://www.ukho.gov.uk/tideprediction.cfm) or my paper tide table booklet.
Port in question is Milford Haven FWIW.
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