Managing Ocean Currents

I have written a lot about weather up to this point in the book, but in many cases routing for the combination of the prevailing weather and any current or tide can be the most important contributor to a comfortable and safe passage. In this chapter I look at a real passage across the Gulfstream and discuss what to look for and how to react, information that will help you in any ocean with currents.

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C. Dan

It’s posts like this that remind me that I’m nowhere near ready for offshore passages as a skipper. Thanks for the important reminder.

One day, though.

Jan-Paul Waldin

John, I have re-read this post in preparation for our Bermuda-NY crossing scheduled to start with the first weather window after June 1, and thank you for the insights.
Is there a router who you would recommend to advise on Gulf Stream entry and exit points? Also, may I ask where you captured that excellent colour graphic of the Stream in your post on the loss of Tao yesterday?

Kind regards,
Jan Waldin

Ernest E Vogelsinger

Hi John,
the graphics on the website you mentioned in your post unfortunately don’t work anymore, the last successful image dates from March 6th, 2019, with increasingly degrading until no data within the 3-4 following days.
Have you got any other source like this?
Thanks, Ernest

Jan-Paul Waldin

Thank you, John, much appreciated.

I think we are on the same page here. I agree entirely with your point on the skipper’s job, and that this responsibility is not delegable. And that certainly applies to routing decisions.

That said, seeking knowledgeable advice, and weighing it with other material factors — including the advisor’s abilities and limitations —knowledge of the capability of the vessel and its crew, etc. etc.,, is central to this process, as it is to all executive decision-making. Seeking advice is one thing, what one does with it is another.

As you have underscored in other posts, (e.g. The Best Weather Forecast You Never Heard Of) wx forecasts themselves are opinions to be considered, and it is invaluable to understand what goes behind them; the same applies to across the board.

Thanks for sharing your insights from your thirty and more years of Stream crossings. I can see another seminar in the making there, if you were so inclined . . .

Kind regards,

Jan

Bill Attwood

Hi John.
I should be interested to know the science/mechanics behind the wind against current phenomenon. Googling the question was a limited success, with the only explanation which made sense referring to the effect of the wind on the elliptical movement of the water in waves. The deeper water continues pushing forward, while the higher water is pushed back by the wind, leading to steeper and breaking waves. Do you or any of your correspondents have a better explanation for the phenomenon? There are a number of shallow water examples around the British Isles, the Portland Race probably being the best known, but I have never had the misfortune to experience one of the major ocean currents.
Yours aye,
Bill

Marc Dacey

As an aside, and because I agree with the argument that skippers should learn to interpret weather data from the level of the deck, I have been learning a lot from this book written by a professional mariner: http://www.chesneaumarineweather.com/?p=214

Stan Creighton

Hi John,
Maybe a stupid question, but I’ll ask anyway. My wife and I cruise in a powerboat so I know what speed to expect for a given rpm in calm water. If, for example I normally cruise at 10 knots and I am now only making 8 knots, can I conclude that I may have up to 2 knots of current affecting me? In other words, is there a direct correlation between my speed and the current? My gut tells me yes, but I cannot find a real world statement confirming this.

I’ll give you more details if you’re interested, but I ask the question because we just had an experience going from New Zealand to Australia. Instead of going our usual 10 knots, we were only making 7 knots as we got into the Eastern Aussie current. This was going on for about 24 hours. Winds were 10-15 knots directly on the starboard beam. Suddenly the wind increased to 30 knots and the seas built rapidly. We then had the closest thing we have ever had to a rollover. I made a number of stupid mistakes and piloting errors. I am trying to get some insight into how to predict current in a real time/real world situation and want to make sure I am making the correct assumptions. BTW, the forecasted current speed at the time in our location was 1.3 knots but we had a boat speed reduction from normal of 3 knots.
Stan

stan creighton

John,
Thank you so much for your thoughtful reply. This is the best explanation I’ve had and it makes total sense. BTW, you and your blog are such a resource for cruisers, thanks for all the effort.

Dave Meindl

There’s a really great pamphlet on navigating the Gulfstream. It comes from a collection of articles written in Ocean Navigator magazine from 1987 through 1994. You can buy it on Amazon:
https://www.amazon.com/Gulf-Stream-Companion-Art-Navigating/dp/B07L5XW6Z2

Ernest E Vogelsinger

Currently unavailable on Amazon, found here: https://www.abebooks.de/servlet/BookDetailsPL?bi=30514753717

Michael Lambert

Thanks John for this and all your articles, including the ones comparing the Garcia and Boréal which first led me here. My first comment/question is this: how do you get accurate waypoints off of those little online gulf steam charts? Tell me it’s not just guesswork based on given Lat/long Lines?