Meteorologist and sailor Chris Tibbs shares his top tips on how to plan the perfect crossing of the Bay of Biscay
Biscay has a fearsome reputation and for many sailors, it is their first taste of bluewater sailing. Distances may not be a huge, but we are out of shelter, in deep water, and away from an easy port of refuge, giving a rather different feeling from sailing across the English Channel or crossing the North Sea.
Although it is less than 400 miles from Ushant to Finisterre, the route is exposed to the full force of the Atlantic and can be dangerous if you try to force a passage against the weather. Going later in the season sees the likelihood of gales increase from around three per cent in September to ten per cent in November.
As the winds increase, the chance of the direction being between south-westerly and north-westerly – creating a lee shore – also increases. Late-season north-westerlies also tend to be short lived, backing to the south-west again rather than veering further north.
Northerly winds that continue past Finisterre, and turn into the Portuguese Trades extending to the Canary Islands, become less frequent. It is not impossible to get this pattern but as winter approaches, it is less likely. This ‘slingshot’ down the Atlantic is what teams wait for when trying to set a Jules Verne non-stop round the world record. Most yachts heading for the Canaries will spend some time waiting for the weather.
Dash to the south
I spent many years as a delivery skipper and invariably we were late leaving to head south. With limited periods of favourable wind between seemingly endless south-westerlies, we would make short hops along the Channel coast before hanging around at Brest for a reasonable forecast, quickly followed by a mad dash to get south of Finisterre.
In November there is still a small chance of north-easterly winds, and I did once experience a fantastic downwind sleigh ride all the way from Cowes to Finisterre. However, the majority of my Biscay crossings have involved time in harbours waiting for the weather to change. A few years ago, at least one boat heading for the ARC was put on a truck and driven south as a seemingly endless passage of depressions made crossing Biscay too risky.
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Historically ships would head as far west as possible before turning south. However, nowadays with accurate weather forecasts, I prefer to wait for a good four-day forecast and reduce my distance and time in Biscay. With under 400 miles between ports, most yachts will happily do this in three days or less, so a good forecast should see us easily across the Bay with a low risk of unexpected bad weather.
It becomes more critical when there is a time constraint. If we look at a typical depression, the initial wind direction will be southerly. That’s fine for getting west before the warm front arrives and the wind veers to south-west, but this is now tricky as neither tack looks good.
Within a low pressure system, the wind always veers, so a port tack towards the new wind is preferable. This also has the added benefit of gaining sea room. But how far to go? We obviously don’t want to over-stand once the front passes through, but neither do we want to drive into the bay only to find that once the wind veers we still cannot lay Finisterre on starboard.
Choosing the time to tack has the potential to win races and give a fast passage across the Bay. Once the veer arrives with the cold front, the north-westerly will last anywhere from a few hours, if the front is one of a family of depressions, to a number of days. In the latter case it will continue to veer to the north, giving an easy exit before the wind changes.
Whatever the forecast there are a number of additional considerations to take into account. The continental shelf extends around 60 miles south-west from Brittany, which can give a dangerous sea state – particularly when the wind swings from the south-west to the north-west and two wave trains combine on the rapidly shelving seabed. A number of yachts have been rolled or lost in this area and even if the wind is favourable, it may be necessary to wait for the sea state to drop.
Another significant feature of the Bay is the funnelling of the wind around Finisterre, particularly when it is blowing from the north-east. General forecasts and low-resolution GRIB files tend to underestimate this, so once you have crossed Biscay there may still be a sting in the tail!
The shipping factor
There is also shipping to contend with; fishing vessels operate inside the Bay of Biscay, while to the west shipping lanes bring a continual stream of large ships.
Choosing a route to minimise time spent among them makes sense and although the TSS does not extend into the Bay, ships follow straight lines between Ushant and Finisterre.
AIS is one piece of kit I would not want to be without and last time I was in Biscay I noticed a significant number of fishing boats also showed up on AIS.
About the author
Chris Tibbs is a meteorologist and weather router, as well as a professional sailor and navigator, forecasting for Olympic teams and the ARC rally.
First published in the November 2017 edition of Yachting World.