Question: We’re planning to sail from New York to Falmouth (UK) leaving around May 18th. Our plan is to sail WSW out from New York till we hit the Gulf Stream and then attempt to sail the great circle to Falmouth. We’re debating whether to consider a more southerly route to stay clear of weather systems? Any views?
Answer: This type of question (asking for a suggested route for a trans-Atlantic passage) has come up several times lately so I’m going to deal with it in some detail.
Route planning, particularly in the North Atlantic, is a dynamic process that starts before departure and continues throughout the passage since the best route is continuously changing depending on the state of several factors.
The goal is to come up with a route that, as far as practical, keeps the sailboat:
- south of low pressure systems, so that the wind is fair;
- north of the Bermuda/Azores high, so there is wind;
- and clear of the ice to the east of Newfoundland.
Also, if it does not require too large a course alteration and does not conflict with the first criteria, it would be good if the route took advantage of the Gulf Stream and any attendant eddies but without risking getting into a wind-against-current situation.
I’m going to explain the process by using real data from today, May 10, and write about how I would react to it. All of this data can be accessed at sea using weather fax and some method of receiving data files like an Iridium phone or Sailmail over SSB radio. None of this needs to be horribly expensive: Equipment costs are in the range of US$1000 to US$4000 and data costs from zero to less than five dollars a day—almost certainly less than that of the wear and tear on your boat that getting hammered several times would probably cause.
But before I start, a couple of cautions:
- Because this is a relatively short post, I will be radically oversimplifying. This post will not make you a competent voyaging sailboat router. It is only intended to illustrate the process. If you want to learn to do this properly, we recommend the Starpath Weather Trainer and Weather Predicting Simplified by Michael Carr.
- As the second chart shows, the North Atlantic, even in late spring and summer, can be a rough place. No amount of weather routing will save you from every gale and storm. If you and your boat are not prepared to withstand a multi-day gale or even a storm, you should not cross the North Atlantic by any route.
Monitor the Path of Lows
Using weather fax, you can monitor the position of the Jet Stream (top map) and particularly the 564mb contour (in bold). As you can see by comparing the two maps, lows and particularly gales generally follow about the same path as this contour. The Jet Stream is a long way south at the moment so I would stay well south too.
As the lows rumble up on my port (hopefully) quarter I would then use GRIB wind field and pressure files (not shown) to refine my course to try, as far as possible, to stay close enough to the lows to have good fair winds but far enough away to avoid gale or storm force winds. As I got further east I would watch the position of the Bermuda/Azores high to make sure I did not get too far into it and lose the wind.
Look Out For the Gulf Stream
Since we are cruising and not racing, I would deemphasize the Gulf Stream except to make sure that I did not inadvertently get into a wind-against-current situation. I can tell you from my ocean racing navigator days that given the choice of sailing toward a fair current or a fair wind, the fair wind wins every time. Of course both at once are nice.
I would be careful of the Gulf Stream. As you can see on the chart, it is not just a nice simple river of water heading the way we want to go. There are plenty of eddies and meanders that can deliver a foul current and even 30 knots of wind apposing the current will quickly generate truly dangerous breaking seas. There is also a higher chance of thunder storms and other violent weather in the Stream due to temperature differentials.
Stay Out of Ice
As you can see, the ice is a long way south at the moment. In fact, this is one of the worst ice seasons in years.
I would stay south of the ice line. Even if the ice was further north, I would stay well south of the Grand Banks, to avoid excessive fog. Though I am experienced in both ice and fog, life is too short to go looking for trouble just to save a few miles.
So in summary and going back to your original question, your basic strategy is a good one and yes, given all the factors above, I would stay well south of the great circle. In fact I would not even think about the great circle. Getting stuck in one gale on the nose for several days will more than wipe out any gains to be had from a shorter distance.