Gentlemen! Start your engines!
09 Nov 2019
Log 00089
It is not exactly true to say that we started with just under 100 miles on our log. We upgraded our chart plotters during the scheduled repairs, and the log got reset. In fact, we have 41 228 NM under our belt, which is yet to be added to the log. But for ease of reference I will stick to the log reading on the new Raymarine, so just keep those extra 41 000 NM at the back of your mind.
The route from the South coast of England to Antigua has been run numerous times over the last 5 centuries or so, and is probably the most documented ocean crossing on the planet. Navigational notes haven’t changed much over time either: head south until the butter melts and turn right.
However, things become slightly more interesting when one must do this crossing to a deadline. And this is exactly what we were trying to do to ensure we could still grab some charter work in the Caribbean prior to the start of the racing season.
Today, with global forecasting services at our side, a yacht can choose whether to opt for a direct, Azores or traditional (Canaries) route in order to arrive in the shortest time possible without trashing the boat in the process. There are a number of global forecasting services that issue both long-range and more detailed, local forecasts. An American model called GFS is probably the best known in terms of WIND. It offers the furthest glimpse into the future at 16 days, but only in a 100 NM resolution. Personally, I find it less reliable than the alternatives, and use it only to understand the bigger picture.
The French models (AROME/ARPEGE) are my favourites for the Channel, the Irish Sea, and the Atlantic. In fact, this will be the default prediction model that we will use when offshore racing (unless, of course, there happens to be a complete lack of consensus between the various models). For those who are interested, the French take weather forecasting VERY seriously. In fact, their Météo service could be held liable if a French citizen ends up in distress due to a poor or lacking forecast. This is why MeteoFrance is generally believed to be the best-funded weather forecasting service in the world.
The British have a very handy tool called PREDICTWIND that ‘cooks’ the original GFS model (as well as that of its European counterpart – ECMWF) based on historical observations, and also tries to take into account local conditions and katabatic winds. For areas favoured by British sailors, including the Solent, the Channel, and Antigua, these models are pretty good. The recent update to their algorithms (2019) seems to have been quite a good one, and for models of 1-3 days this service has historically proved to be much more reliable than the original GFS.
For wave height and direction, the default is an American model WWIII. Realistically there are few alternatives. However, it is important to always bear in mind that the development of waves is secondary to wind and pressure! And WWIII (rather obviously) employs the GFS forecast for its inputs. So in a situation where there is a significant difference between the American wind model and whatever you might be using, it is prudent to remember that WWIII would most likely also be off. And then the trick is to consider the differences between the models and make an appropriate adjustment to the WWIII model.
And, finally, ocean currents have quite a significant impact on passages like ours. Common sense suggests that going with the current will take you to your destination faster than fighting the current all the way. Luckily for us currents are well studied and quite constant. TIDETECH is my tool of choice, and uses the MERCATOR global ocean forecasting system to issue a forecast 7 days in advance. Just to make the navigator’s life that little bit more fun, MGOFS is based on the European wind and pressure forecast ECMWF, so can at times be quite different to the wave model in its raw underlying data.
Ah! I almost forgot! There are also things called tidal currents. These have a considerable effect in the Channel as well as the north European Atlantic coast. Generally, the chef and the guys below decks don’t enjoy the ride when the yacht is battling with the tide. Again, I rely on TIDETECH to take tidal streams into consideration.