OVERVIEW
The Bay of Biscay is a notoriously dangerous sailing area and noted among sailors worldwide for its rough seas. Up until recent years, it was a regular occurrence for merchant vessels to founder in Biscay storms, particularly so in the winter. The primary reasons for its fearsome seas is the continental shelf that extends into the northwest section of the bay, and how it interacts with the Bay’s prevailing winds and storms. The below image, published in fall 1993 issue of Mariner's Weather Log, shows a Merchant ship with one of the huge waves that are common near the 100-fathom curve on the Bay of Biscay.




The continental shelf is an underwater landmass in Biscay that creates a coastal shelf of relatively shallow water extending out into the sea. The shelf is up to about 100 miles (160 km) wide, off the coast of Brittany, narrowing to less than 40 miles (65 km) off the Spanish shore as shown in the bathymetric map below. The inner part of the shelf is shallow and fronted by a ragged leading edge that is dissected by numerous submarine sheer cliffs and canyons. The change from deep to shallow waters has the effect of steepening the Atlantic swell and because of this abrupt and irregular leading edge in Biscay, the seaway above can become confused and extremely rough even in a moderate storm. During early autumn the situation is sometimes exacerbated by a high Atlantic swell generated by a hurricane blowing thousands of miles away.




A quick example to illustrate this phenomenon can be seen on a route planning chart. If a direct route is drawn upon a chart from Kinsale to La Coruña a route of approximately 180° T, most viewers will be surprised to discover 240 miles due south from Kinsale Harbour there is a special purpose marker buoy. The isolated buoy, located in the centre of the bay, is called 1GB. It marks the positioned of Banco Perueno Sol where over a distance of 20 miles the depth changes from approximately 5,000 metres to 120 metres. Grimley, the surrounding area on the chart can be seen to be littered with consequential wreck marks.

The prevailing winds and currents are also a challenge as they have a tendency to set towards Ile d'Ouessant, in the north, and into the Bay of Biscay to the south of it. This places a southbound vessel on the starboard tack which has a tendency to set the vessel south by south-eastward or southeastward. These tacks only serve to embay a vessel and make it vulnerable to a southwest gale, which is the usual direction of the worst gales. All of this makes a southbound voyage across the bay the more difficult direction.




Gales in the bay can be severe and winds may exceed 70 miles (113 km) per hour. Squalls are also a hazard to navigation and may occur at any time of the year. A large portion of this is due to local conditions in Biscay. The Bay of Biscay re-circulates a portion of the North Atlantic drift around in a clockwise circulation. This brings cold moist air into collision with hot Spanish mainland air currents that develops a series of cumulonimbus clouds. The result is turbulent weather systems and line squalls in the bay area and a high degree of instability along the north coast of Spain.

The indraft of the bay is at its strongest during gales where a yacht could easily find itself in survival conditions. If embayed in the Bay of Biscay, any change of the wind to the west would necessitate beating to windward against the current which could make it very difficult to weather Cabo Finisterre or even Cabo Ortegal. It should also be noted that the Atlantic swell can build up rapidly near the coast here and a number of ports can become dangerous to enter or even inaccessible.




All of this can all be avoided by taking a route outside of the Bay of Biscay. The tack out to the west loses nothing in most events as the wind will generally be found to veer out west. That change of wind will be favourable and even permit a vessel to pursue a direct course with a free wind.

Finally, the overall passage will generally be found to be easier by passing over the obvious landfall of La Coruña. La Coruña is very tempting landing port as it shortens the trip but it has its own complications. 50 miles out from La Coruña the depths step up from 5,000 metres up to 120 metres over a distance of 10 miles. This steep shelving, when combined with rough local weather conditions, is best avoided.




Likewise, it is worth giving Cape Finisterre a wide berth. The Atlantic current usually sets right on-shore here and when combined with a pronounced local weather microenvironment at the cape, locally known as the Costa da Morte, which means Death Coast, causes it to be a foul corner as often as not. This is further complicated by the weight of commercial traffic within the Finisterre traffic separation scheme, reaching out to 10° west, that has to be negotiated close offshore.




All of this can be avoided by keeping far enough out to sea and passing south to Bayona or beyond. Bayona does make an excellent landfall. Well protected in the Vigo estuary, the harbour allows boats to enter via the North Channel which offers the early protection of the Bayona Islands.

For those who do not want to go to go as far northwest as Ireland, the traditional trading route for old sailing vessels was to depart the Channel, going west of Ushant and out to or a little further than 10°W. That well-tested approach stands the test of time today. The ideal port to depart from the English Channel is the very serviceable port of Falmouth on England’s southwest corner. If the wind is from the west keep on a tack which enables most westing to be made to get a good offing, and keep clear of the Bay of Biscay, even standing northwest until well intersecting this route to pass outside Cape Finisterre on the starboard tack.


On the whole, this Atlantic route may be longer but it allows a vessel to stand well clear of all the rough water and disturbed seas upon the shelf in the Bay. It also avoids all the unpredictable weather upon Spain’s northern coast and the dense shipping traffic moving around Cape Finisterre.

LISTED WAYPOINTS
The complete course is 611.90 miles from the waypoint 'Kinsale Harbour Initial Fix' to 'Bayona Initial Fix' tending in a southerly direction (reciprocal northerly).






PLANNING NOTES
Any vessel attempting this route should be of a deep ocean class and in excellent seaworthy condition. It is also important to plan the passage around a good weather window.

Weather is the most important consideration for most sea or ocean passages and never more so when crossing the Bay of Biscay. General forecasts for 6 or 7 days are of sufficient quality to be used operationally. Do not leave if southwest winds are forecast, as these are typically generated by a North Atlantic depression. Summer depressions normally pass to the north of the area but they can drift south depending on the position of the Jet Stream. As soon as any depression has passed, northwest winds can be expected and with the benefit of a reasonable long-term forecast, there is usually sufficient time to pass Cape Finisterre before another change occurs in the weather.




Using Kinsale Harbour as the point of departure, set out on a bearing of 210° T for approximately 100 nm aiming for the waypoint of 50° 00.000’N, 10° 00.000’W. At this point of the passage, the less steep northern section of the shelf is approximately 75 miles ahead and will most likely be crossed the following day. It is, therefore, advisable to batten down the vessel and be prepared for any rough seas that could occur when crossing.

After crossing the waters will be found to be discernibly more settled and taking on the pattern of the deep Atlantic swell. Continue on the 210° T bearing after the continental shelf has been crossed until 10° west has been attained. The options then are two-fold:

• • In good conditions track down south on 10° west outside the shelf.


• • In rough conditions keep going out on the course of 210° T until 11° west and then track down south.

Pass down beyond La Coruña and Cape Finisterre, outside the western edge of the Finisterre TSS (traffic separation scheme) by steering to the waypoint of 42° 40.000’N, 10° 00.000’W. In 2004 the Finisterre TSS was revised to consist of two northbound and two southbound lanes, the closest to the shore being 21 miles and the furthest 42 miles, and the waypoint is well outside this.

From there it is possible to turn in on a final bearing of about 120° T for Bayona approximately 55 miles away. There you will cross the continental shelf very quickly in the much more settled conditions south of Cape Finisterre. The listed Bayona initial fix waypoint of 42° 08.000’ N, 008° 57.000’ W is 1½ miles off the northwest end of Pt Lobo De Silleiro and 4½ miles outside the harbour.

What is the best sailing time?

The best time to take this route is in early Summer, between May and July, when the weather is often settled and the winds are favourable, possibly even veering to the northeast. During these months, storm force wind events are extremely rare in the Biscay sea area. However, severe gales are always possible near the Spanish coast in the Summer as the Spanish heat low deepens during the day, especially when the Azores high intensifies or moves a little to the east. So it is essential to maintain a vigilant watch upon the extended range forecasts.

Towards the end of summer, the frequency of gales increases and more attention should be paid to the forecasts from the middle of August to the end of September when some of the most violent storms have been recorded. During the rest of the year, excessive winds are common.

Are there any security concerns?

Never has a security issue known to have occurred to a pleasure vessel sailing this route.

With thanks to:

Burke Corbett, Gusserane, New Ross, Co. Wexford.