92 November 2017
iscay 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 crossing
the Channel or 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.
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 yachtswill 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 potentialto 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!Weather briefing
CHRIS TIBBS ON CROSSING BISCAY
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.THE SHIPPING FACTOR
PRACTICAL
Chris Tibbs is a meteorologist
and weather router, as well as a
professional sailor and navigator,
forecasting for Olympic teams
{ and the ARC rally
}Weather briefing
CHRIS TIBBS
B
Average wind speed
and direction measured
by satellite for 16-31
October, 1999-2009.
At this late point in the
season expect delays
sailing south across the
Bay of BiscayLa Vieille lighthouse marks the end of the Raz
de Sein to the north of the Bay of BiscayOregonstate.eduHemis/Alamy