Crossing Biscay

Crossing Biscay

Thursday, November 10, 2016

Chris Tibbs, Sailor, Meteorologist and Raymarine Pro Ambassador draws on his wealth of knowledge and experience to highlight key weather insights that will help you safely and competently cross the Bay of Biscay.

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Biscay has quite rightly got a fearsome reputation and pictures of lighthouses engulfed in waves are often taken near Brest. However it is also possible to have quiet crossings and in the past I have even ended up motoring all the way across in a flat calm. Around the coast of Biscay there are also some great cruising areas and the northern coast of Spain is spectacular.

With families of depressions crossing the Atlantic we get a regime of strong winds changing from SW to NW then back again, square rigged ships with huge tacking angles would become embayed in Biscay unable to beat out of the Bay. An unforgiving coastline along with hostilities against France and Spain gave sailors nowhere to go. Crossing Biscay was difficult and dangerous and some ships waited weeks for a northerly wind to get them safely past Cape Finisterre.

There is however a great deal of difference between the expected weather of high summer and that of spring and autumn although this year (2016) we have hardly had a settled period. In the summer, when the Azores high is well established, statistics tell us that there will be a ridge of high pressure extending from the high towards Brest; this gives us the predominately SW winds in the Channel, W’ly in N Biscay and a N-NE’ly in south Biscay. The semi permanent heat low over the Iberian Peninsula then accelerates and bends the N’ly into the Portuguese trade winds.

This is the settled summer weather pattern, but some years the jet stream remains well to the south allowing lows to pass close to, and over, the UK which in turn gives us predominantly SW’ly wind in Biscay with conditions more like spring and autumn rather than midsummer making crossing Biscay rather more difficult.

When depressions dominate the weather a large swell develops and as this hits the continental shelf (which extends some 60 or so miles SW of Brest); the shallower water causes the swell to increase in height and for it to shorten in wave length. If the wind then veers NW, as it will with the passage of a cold front, a dangerous and confused sea can develop and this is where a number of yachts have got into difficulties over the years.

In modern yachts with good windward performance and long range forecasts, the dangers of Biscay can be minimised. That said yachts still get into difficulty crossing the Bay which is usually due to time pressures and the inability to wait for a good forecast.

With the ease of access to the internet before we leave and a massive amount of available forecasts there should be no excuse in getting caught out although once we slip our lines, getting a forecast at sea generally means relying on the shipping forecast and what is available via VHF, and whilst many ocean cruisers have satellite communications, it is an expensive luxury. It is therefore important to get a good 5 day forecast before leaving and to make as much progress as possible.

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An exciting new way of doing this is to download Grib files directly onto our Raymarine MFD. This can be done using the marina WiFi, or a mobile phone hotspot. With a Theyr weather forecast account we get good quality forecasts directly in front of us without the need for additional computers and equipment.

On the MFD we can not only get the usual wind speed and direction but also pressure fields and rainfall. What is particularly useful for Biscay is a sea state forecast as this is important when crossing the continental shelf and on the approaches to Finisterre.

One feature that I particularly like is the ability to animate the weather as it gives a real indication to the dynamic nature of the weather.

Although the grib files are full of information I would still download synoptic charts for positioning fronts and it is still very important to listen to the marine forecasts as these are prepared using additional information and will give warnings particularly on visibility, thunderstorms, and strong winds.

Many cruising guides advise getting well to the west before pushing south; wise words if there are depressions approaching however I would rather start from near Brest to shorten the distance. We can then make a decision depending on the weather forecast. If it is currently SW’ly ,the next direction is likely to be W-NW which allows me the option to push west until the front arrives, or to wait in port with a bottle of red wine until the wind swings NW and off we go. During the summer months a short wait should see the wind swing more to the N making for a more pleasant crossing but Spring and Autumn will see more persistent SW’ly winds.

Although it is preferable to cross and get around Cape Finisterre in one go, sometimes it can become a race to get across the Bay before the next front comes along and spoils the fun. On our last crossing we headed for shelter in Celeiro one of the Rias to the east of La Coruna to avoid strong headwinds. Approaching the coast low cloud and drizzle reduced visibility considerably. There were lots of fishing boats around but as the majority had AIS there were no near misses and any without AIS were picked up clearly on radar. With the MFD working as a chart plotter along with the radar much of the worry was taken out of arriving at a new port at 0300 although fish pots still had to be dodged.

There have been a number of significant changes to our sailing over the years; GPS was the biggest game changer but AIS has now helped with a big jump in safety. It is reassuring to know where ships are heading and if there is a convergence of courses. Not all vessels have AIS but I for one have it high on my wish list when voyaging offshore.

The availability of forecasts in grib file format, the internet, and MFD’s that show and animate the forecasts, all bring the weather to life. There will always be localised weather, squalls and acceleration zones around headlands etc. but the more information we have the less likely we are to be caught out by the conditions.