Direction of tidal currents

Every year I buy…
Tidal Current Tables _____, Pacific Coast of North America and Asia, formerly published by NOAA. Tidelog’s Puget Sound edition is pretty good, too. Additionally, I have a Washburnes Tables keyed to the Strait of Georgia and Strait of Juan de Fuca. My Navigation library includes Burch, first and foremost, then Ferrero and Moyers books. Additionally, if you are planning any forays into the PNW, I would advise a look at Jeff Renner’s Northwest Marine Weather.



As Flatpick said, you should know what the water is doing around here before you get on it, or whatever he said. Understanding the tides is easy to learn and maintain. For what it’s worth, the nautical charts and understanding symbology are pretty important. Winging it might get you by for a while, but mother nature can get pretty dismissive of the careless among us.



Dogmaticus

web sites
I paddle in and near New York Harbor, and I check tide predictions regularly, for two reasons. First, while there aren’t many places around here where the tidal current is strong enough to completely prevent paddling, it can make a big difference in how long you need, and how tired you get, for a given distance. Second, the relationship between current strength and water level is hard to predict: At my club, the max level occurs at about the same time as the max flood current, while you would think it would occur at slack water. But at Hell Gate, seven miles away and in a different part of the harbor, the intuitive relationship holds.



I imagine the importance of local knowledge of the tides depends completely on where you are. Some places have a weak enough tidal current that it doesn’t matter much.



I get my predictions from Eldridge, wunderground.com’s marine forecasts, tbone.biol.sc.edu (which has all sorts of fancy plotting options) and, most interestingly, from tidesandcurrents.noaa.gov. I suspect the NOAA site has the original data that all the other sources use (they’ll even sell you the FORTRAN code for running your own predictions). In particular, NOAA has two kinds of current tables: the tables for primary locations, with predictions based on computer simulations, and the tables for secondary locations, which just give never-changing time differences relative to the primary locations. For instance, the East River at Hell Gate is a primary location, since it’s so scary, and then the middle of the Harlem River is just given as “20 minutes before Hell Gate.” I learned a lot about how the currents travel around the harbor by studying the secondary-location charts.



– Mark

REEDS
is a great resource.



yeah, i always check

But are they accurate?
Somewhere on the NOAA site about current stations and data there is a little comment that many of the calculations, in particular the secondary stations, are old and are not considered to be accurate. So while you may see all these nice current charts in books and your computer may produce reams of data about such stations, I wonder just how accurate it all is. I rather suspect the current station data near major shipping lanes is timely and good. Extrapolated data and station data from less important primary stations might be good or might be junk.

SK and MarkinNC Are Correct

– Last Updated: Dec-02-06 2:22 PM EST –

at least regarding the sounds of NC. The direction and speed of the wind matters a lot. The amount of fresh water emptying into the sounds has got to be an influence as well.

I think the most important tide information is when high and low are right AT the inlet. In the creeks, rivers, and sounds the tide can make you tired and miserable. At the inlets the tide can kill ya.

Nobeltec
Nobeltec Tides and Currents software is an excellent program for info. Not free, but not super expensive. Covers all of North and Central America and Hawaii.



All tide and current prediction data are just that. Predictions.



Tides can be altered by weather. Even weather far away.

Getting back to the actual question
I’ve only had a chance to scan this:



http://eezway.org/clinic/Oceanography/Resources/Tides.pdf



But it looks like an excellent and comprehensive reference on tides and tidal currents.

importance of local knowledge
We spend most of July on Muscongus Bay. None of the nautical almanacs nor the Coast Pilot have much information on tidal currents for this bay. When I asked a resident about sources for such information, his reply was “That’s what they call local knowledge.”



So, we started noting the currents, and next summer will start recoding our observations so we can use the currents to our advantage.



(The number of islands and depth variations results in a marvellous array of tidal current direction and speed)

I’ve read that
they got it all wrong

Is it accurate? Look at these…
http://tinyurl.com/yyape5



http://tinyurl.com/y2p63j




Thank you all, plus a tidbit of info:
Wow, I really didn’t expect many replies to my question. Wouldn’t you rather argue about skeg vs. rudder, soft vs. hard chine? :wink:



Sounds like figuring out a specific place/time can be tricky. But I suppose if it were all cut-and-dried, it would take some of the wonder out of paddling.



Here’s a comment made by the guy I referred to in my initial post. Little did I know he read my post, till he e-mailed me saying he was working in the deep freeze of Alberta. He said I could quote him, so I will give exact quote of part of his advice (boldface added by me):



Current changes may lag tides considerably. If there’s a large basin “inland” from where you are, it has to keep filling long after you reach high tide. The reverse is typically also true. Baja is a good example. In the middle and southern part of the Sea of Cortez, tides and therefore currents are small. In the northern part however, tidal range goes up dramatically. It might be only 2-3 feet in Loreto, but will be 8 feet or so in LA Bay. Since the basin continues a couple hundred miles north, you will hit high tide at LA Bay, long before you hit high tide further north. So even though the tide is beginning to drop where you are, it’s still filling to the north! and you have a current against you (flooding north) paddling south while the tide is dropping. There’s no current tables for the area that tell you this, but if you study up on the basic principles it makes sense. What’s harder is to try to predict the times of these movements.

Is It Accurate for Currents?
The question was not about tide levels, it was about currents. My point was that NOAA states the tide current primary and secondary info, except at locations where there has been recent observations, tends to be dated and should not be considered accurate. All the publications and software rely upon the same NOAA dataset AFAIK and, therefore, one needs to take the predictions with a grain of salt in many cases.