To understand what lies ahead for Marc Guillemot at the helm of Safran, we have to look at the major weather patterns he will face as he sails around the world. Sylvain Mondon, engineer and meteorologist, summarizes what he can expect.
“With two days to go to the start, it is still rather too early to say exactly what lies ahead, as we are in a transitional phase,” Sylvain warns us. “To sum up, in the first stretch from the Bay of Biscay to the Canaries – there are two possible situations. Firstly, the one that is most common in the autumn: a series of low-pressure areas with several associated fronts. That leads to fairly strong westerly to south-westerly winds. That is what happened four years ago and led to heavy seas, forcing boats to retire early in the race. The second scenario is the presence of a high-pressure area. If the centre of this high is close to the continent of Europe, the fleet will face light northerly winds. But if this high is situated to the north or over the Azores, it leads to strong north-easterly winds, so a very fast start.”
Doldrums, St-Helena, the southern ocean…
And then what? “To the south of the Canaries, we enter the area of the north-easterly trade winds, which back easterly as we approach the Doldrums. Marc and the others should enjoy fast sailing here, downwind or reaching on the port tack.” They will then need to think about where exactly they will cross through the famous Intertropical Convergence Zone (ITCZ). “It is here that the trade winds from the northern hemisphere meet those from the southern hemisphere. Thunderstorms develop quickly and can be violent: the wind is never what you want. Sometimes there is too much, with winds up to 55 or even 60 knots… and sometimes not enough with many hours of being becalmed with the wind completely absent. The way through is somewhere between 27° and 33° west, to the south of the Cape Verde Islands.”
From the Doldrums to Brazil (at the latitude of Salvador da Bahia), “Safran will be sailing in the trade winds in the southern hemisphere, which blow from the east to south-east and freshen. On the port tack, they will then have to get around the ridge of high pressure from the St-Helena high, which can stretch right across to the north of Brazil. This is the problem they have to deal with until they reach the Roaring Forties. What they need to do is get down to the disturbed air stream in the southern hemisphere by getting around the area of high pressure. If the situation is favourable, that happens at around 35° south, but if it is unfavourable it can be right down at 45° south” or in other words, 600 miles further down.
That is what Safran is going to have to do to be able to round the Cape of Good Hope. In the southern ocean, passing through the Indian and then the Pacific Oceans all the way to Cape Horn, there is an identical problem: “They have to make the most of the disturbed air stream by reaching the edge of a front generating north-westerly winds ahead of it and south-westerly winds behind it. That is the real challenge of rounding the Antarctic: Safran will have to use the downwind conditions offered by the various fronts, while avoiding the areas of high pressure to the north of the direct route. There is an additional difficulty here: they have to respect the ice gates (compulsory marks to limit the risk of encountering icebergs), which in some cases, may force the skippers back up to areas of light winds.”
Watch out for cyclonic conditions
Cape Horn marks the way out after this tricky and physically tough stretch. “But a word of caution,“ Sylvain warns us, “in the climb back up the South Atlantic, there are more major difficulties. The trickiest area is the area of cyclogenesis (where low-pressure areas develop) off Argentina. This is the most complicated area in the whole of the round the world voyage, particularly as after around sixty days of sailing, the skipper will be tired and the boat rarely at 100% of her potential.” He tells us more. “Low-pressure areas are fast moving and the weather forecast models find it hard to represent these systems accurately. It is therefore very tricky to find the right trajectory. This is where the experience of the skipper really pays off, as the navigational software is not that much use. It is in this precise area that we can see that man is better than the machine.”
After that, they will find themselves once more off Brazil, “We are of course back with the same situation as in the first part of the race: the same weather patterns.” Sylvain adds however, ”One of the final traps is between the area of cyclonic activity and the route around the St-Helena high, as this is usually an area of thundery activity. This is one more hurdle to cross, before they have to deal with the weather systems seen at the start, but in the opposite direction: south to south-easterly trade winds, the Doldrums, north-easterly trade winds. To finish, they will have to hop onto one of the low-pressure areas crossing the North Atlantic in order to head for les Sables.” Not always as simple as it sounds. “If Safran and the others finish with high-pressure in place (see the explanation early in this article), they will have to go a long way north, almost up to Ireland, before sweeping back down to the finish.” That is exactly what Vincent Riou did before winning the 2004-2005 Vendée Globe.