Regatta: Vendée Globe: the difficult route through the South Atlantic

As he does every weekend, the British professional skipper analyses the weather and racing conditions for the coming days. He completed his studies late on Saturday evening, when nothing was known about the structural problems on board Alex Thomson's "Hugo Boss" that changed the top ranking overnight.

Thomson is currently sailing at a greatly reduced speed so as not to jeopardise his boat, but has remained on course for the time being. We will report in detail as soon as we have news from his team about the exact severity of the damage and its possible cause.

Here is Will Harris' outlook on possible routes to the Cape of Good Hope and why the South Atlantic will be trickier than the previous Vendée Globe four years ago:

"The leading skippers couldn't have wished for a better passage through the Kalmen last week. Hardly anyone was slowed down or suffered massive losses because they got stuck on the wrong side of a cloud - as is so typical for the zone north of the equator.

For the following group of boats, things look a little different at the moment. Pip Hare on "Medallia" and Arnaud Boissieres on "La Mie Caline", who are currently crossing the doldrums, have to deal with a minefield of windless zones. The Doldrums are extremely difficult for them.

Far out in the South Atlantic, on the other hand, the leaders had several days to consider their various options for reaching the Cape of Good Hope, some 2,400 nautical miles to the south-east.

It was anything but clear which path they should take. Normally, they would hope that a clear "path" would show up in the ensemble routings. However, the South Atlantic looks rather complicated over the next few days as the Saint Helena High shifts westwards, leaving behind several light wind zones.

Let's first take a look at the details of the leading trio. We have seen how Alex Thompson on "Hugo Boss" left the Doldrums with a considerable lead of 100 nautical miles over "Apivia" and "LinkedOut". Alex then decided to take a more westerly route than the other two and steadily lost miles to both.

An interesting tactical question is why he did not simply position himself between his rivals and the "route" to the Cape of Good Hope? Perhaps it was because he thought the route to the west was a little faster. It could also be because Alex assumed that his boat would be faster with the resulting wind angle and that sailing the extra distance would pay off. This was clearly not the case. Instead, it was possible to observe how quickly such a lead can disappear.

The South Atlantic has some special features: Firstly, there is the Saint Helena High. This drives the trade winds of the South Atlantic, but it is also very important for the strategy towards the Cape of Good Hope. The position of this high pressure zone can change rapidly as it interacts with the other weather systems in the area. Therefore, a good understanding of what state the high is in needs to be in place before considering a course to the Cape.

Another feature is the South Atlantic Convergence Zone (SACZ). This is basically the meeting point between warm air from the north and cold air from the south, which begins along the Brazilian coast and extends south-eastwards into the South Atlantic. It creates ideal conditions for cyclogenesis and low pressure systems regularly form along this convergence zone.

Both features will be relevant for the strategy of the leading skippers over the next few days. A low (L1) has formed along the SACZ and is moving south-eastwards. The Saint Helena High in the north-east and a larger area of low pressure (L2) in the south are forcing everything to converge. By Monday morning, L1 is absorbed and disappears, leaving a large area of light winds on the direct path to the Cape of Good Hope. When L1 disappears, it also creates a clear path for the Saint Helena High to move to the south-west.

What does this mean for routing?

Initially, sailing towards L1 seems to be the best option as it offers fast space wind conditions. The complication is that there is little wind left after the depression dissipates. The only option is to find a route to the south. Those further ahead, such as "Apivia" and "LinkedOut", will do better with this strategy as they are closer to L1 and can make the most of the good wind before it disappears. However, they will also have to be prepared for numerous energy-sapping manoeuvres, as the wind corridor is quite narrow.

The other option is to sail further south for the time being and effectively try to sail west of the Saint Helena High and L1. This route means travelling a lot more distance, and initially in fairly light winds. But later, once you're far enough south, you'll have fast room sheet conditions all the way to the Cape of Good Hope.

Those further back will fare better with this strategy, as the Saint Helena high will have had more time to establish itself in the west and then slowly move eastwards again, making the route shorter.

Judging by the courses of the top 10 in the fleet, the fastest skippers so far think the westerly option is too much of a risk as it requires so much extra distance. However, there is still the option to break away. Perhaps we will see some take a gamble.

For now, it's great to watch the battles for position at the very front - a study in the performance differences of the Imoca 60s at the cutting edge of design. As the fleet approaches the Southern Ocean, we'll get a better idea of how these designs perform in the extreme conditions and who comes out on top."