Once a week, experienced offshore professional and navigator Will Harris analyses exclusively for YACHT online what challenges await the Imoca skippers. Today: about the baptism of fire at the start of the Vendée Globe, about the high-speed chase that has just begun in the trade winds, and what surprises await in the horse latitudes near the equator:
"Seven days have passed since the start of the Vendée Globe and it has been difficult to keep up with the amount of news and events. Two front runners and favourites, 'Charal' and 'L'Occitane', are already out of the race for victory. Both suffered damage to their boats during the strong cold front that passed over the fleet last Wednesday.
The complicated weather conditions have meant that the modern foilers have not yet been able to fully utilise their ace. With each storm system in the North Atlantic, a short steep sea has developed, making it very difficult to make the boats 'fly'.
The slower designs with centreboards, which had taken a more direct southerly route away from the cold front at Cap Finisterre, were actually able to take the lead - albeit only temporarily. This more southerly route initially appeared to be too light winded in the forecasts, but at the moment Jean Le Cam, who led this southerly group from the start, is in 2nd place overall, just 30 nautical miles behind Alex Thomson's 'Hugo Boss'.
Finally, the fleet had to deal with the subtropical storm Theta in the last 48 hours. It crossed directly in the path of the fleet on its route south, and when the skippers developed their strategies before and shortly after the start, they probably didn't expect it to develop into a record-breaking storm.
We have seen some co-favoured skippers such as Charlie Dalin on 'Apivia' and Thomas Ruyant on 'LinkedOut' who decided to sail around the storm and deliberately took a wider and slower route to avoid the worst of it. Alex Thomson, on the other hand, who is currently in the lead, did not throttle back and sailed to within 70 miles of the core of Theta, where he reported winds of up to 60 knots at times. This risk, which according to his team gave him a hairy patent jibe, seems to have paid off.
The fleet will be grateful to have finally achieved more stable weather. The trade winds are a typical wind regime that is influenced by the Azores High. They lie to the south of the anticyclone and their strength, direction and position are determined by the position of this high.
Typically, the trade winds in the northern hemisphere blow from the north-east at an average of around 15 to 20 knots - allowing a fantastic and fast reach to the equator. Between 7 degrees north and 20 north (the fleet is currently at 23 north), the trade winds are fairly constant. Above 20 north there is more influence from other weather systems. When the storm Theta broke through, the trade winds above 20 north dropped completely, which is why the skippers moved to the west last week. Trades are still being weakened by Theta today, but the low is quickly losing strength and influence.
Now the majority of the fleet is sailing in these steady trade winds and can sail a direct route south and to the Doldrums at around 7 degrees north, which they are expected to reach on Wednesday. These are ideal conditions for the Imocas with foils. Fairly flat water and a stern wind mean that impressive speeds can be expected, especially from the latest generation.
Over the next few days, it will be a pure speed race. Who has carried out the most tests and optimised their boat for these conditions? It only needs a speed advantage of 5 to 10 per cent to be able to pull away quickly. A lead of 100 miles, as Alex Thompson has on "Hugo Boss", can easily double - or disappear - within 24 hours. So keep an eye on the tracker. It will be revealing!
The other thing you should consider is the passage of the Kalmen Belt. Skippers need to position themselves relatively early for this. The calms or 'doldrums' are a band of light winds centred on the Inter Tropical Convergence Zone (ITCZ).
It is the convergence of the trade winds from the northern and southern hemispheres. Low pressure is generated by convective activity, causing air to rise. Large cumulonimbus clouds form, causing light and irregular winds at the sea surface. This zone is complicated to navigate and requires constant attention to choose the best route through it.
At this time of year, the Doldrums are between 7 and 4 degrees north, so this band is about 200 nautical miles wide. They are also wider off the West African coast, so we won't normally see anyone sailing east of 25 degrees west.
Typically, the fleet will compress as it approaches the calms. The leaders sail into the lighter winds first, allowing the boats behind to catch up. But the boats that leave the notorious area first and reach the trade winds of the southern hemisphere first will extend their lead just as quickly.
Due to the complexity of the Doldrums, it is extremely difficult to produce a weather forecast for the participants. Forecasts for this area are generally quite unreliable. Instead, skippers must use satellite imagery and look at the winds in the upper layers to determine the best place to cross the region. Just a few 100 metres of east-west positioning can make a big difference. Catching the wrong side of a cloud can leave you stuck in a wind hole for hours.
Looking at the forecast now, the Doldrums appear to be in a relatively stable phase. The triangle of light wind extending westwards from the African coast is quite small and the orientation of the ITCZ is directly east-west; it does not meander north or south. However, this situation can change completely in less than a day.
The next few days will undoubtedly be fascinating. Who will make it through the doldrums first? In the course of the Vendée history, the boat that manages this usually has a very good chance of winning the race overall. This is because once the Imoca skippers are sailing in the southern hemisphere, the fleet splits into different weather systems. Overtaking opportunities then become rarer. It is therefore possible that Alex Thomson's willingness to take risks when passing Theta could have already brought about a kind of preliminary decision - at least if he masters the horse widths with similar fortune and determination.
Jochen Rieker
Herausgeber YACHT
