The Volvo Ocean Race fleet is now a couple of days into Leg 2 and the first big strategic hurdle is looming large on the horizon – the first of several climate zone transitions that the fleet will have to make on the way to Cape Town. If you’re not familiar with climate zones or the overall strategic picture for Leg 2, please have a look at the leg preview.
If you don’t have time to click through, the main takeaway point is that the earth’s oceanic climate features distinct bands, lying horizontally and looping the globe, running out from the Equator to the Poles in a mirror image.
On the way to Cape Town the fleet will make several transitions from one climate band to another, and these are the moments when conditions can radically change and gains and losses can be big.
The first transition that the fleet will face is from the trade winds into the Doldrums, and it will be the next 24 hours when the fleet will have to set up for this make or break moment.
The trade winds are the moderate to strong winds that blow consistently towards the equator from the north-east in the northern hemisphere, and the south-east in the southern hemisphere. So there are two belts of trade winds that girdle the globe, each blowing towards the equator.
The point where those two trade wind breezes meet is called the Doldrums (or intertropical convergence zone (ITCZ)), a region of low pressure that envelopes the earth’s oceans roughly at the equator. It occurs because warm, moist air rises (relative to cold air), and there’s plenty of that in the tropics. The Doldrums are famous for thunderstorms, light winds, rain and sudden unexpected gusts – not a place you want to hang around.
So this leg is often settled by the first boat to exit the Doldrums, racing south at pace while the rest of the fleet wallows behind still trying to escape. And the big picture strategy for the first week of racing on Leg 2 is to line up to cross the Doldrums at the thinnest point to ensure a fast transition into the trade winds on the other side.
And ‘normally’ the further west you go, the thinner the Doldrums get. The lore goes way back on this one – back to the days of clipper ships – and it says that the sweet spot is around 27-28W, but anything between 25W and 30W can work.
The strategic dilemma here is that while the best place to cross the Doldrums might be to the west, the course to Cape Town is due south. This is the same conundrum we saw in Leg 1 – speed versus distance. To get west and sail through the Doldrums at the theoretical fastest point, a boat will need to sail more miles than if they just pointed straight towards Cape Town. So which will be more important, maintaining a higher average speed, or doing the shorter distance?
So much for the big picture, the fleet has been treated to some great downwind sailing from the get-go this year, starting off Lisbon in a strong northerly breeze that quickly shifted round to the north-easterly trade wind direction and then blew even harder – as we can see in Image 1.
Image 1 - © Geovoile
The wind shift from the north to the north-east can be seen in the slow curve that the boats took, going from a south-westerly course to sailing west. Given that Cape Town is due south of them, it was only a matter of time before someone gybed, and as we can see in Image 1, that someone was MAPFRE just after 01:00UTC on Monday 6th November.
Once MAPFRE had gybed it set off a chain reaction with the rest of the fleet quickly following. And over the next thirty hours the fleet went on a gybe-fest, as we can see in Image 2 from 0900UTC this morning, Tuesday 7th November.
Image 2 - © Geovoile
What was happening here was that each boat was using small shifts in the wind to get either south (shortening the distance) or west (setting up for the fast route through the Doldrums). The average wind direction was blowing from the north-east, so when it shifted towards the north it made it more efficient to get west on starboard gybe; and when it shifted more towards the east, it made it more efficient to get south on port gybe.
The skippers and navigators picked the gybe they were on depending on the size and direction of the wind shift, and how much emphasis they wanted to put on getting west, versus south.
All of that action has led to the relative positions of the fleet this afternoon, which we can see in Image 3 from 13:00 today, 7th November. Dongfeng Race Team and MAPFRE are in the best shape, separated by about 40nm of leverage running north-west to south-east – both boats are a big jump south and west of the rest of the fleet.
Image 3 - © Geovoile
They’ve achieved this with a series of small gains, playing the shifts, rather than any major strategic moves and these gains will remain important in the battle to get both south and west.
If we look at Image 4, we can see the big picture very clearly. The two jets of trade winds blowing towards the tip of West Africa, and the blue patch of Doldrums where they meet. It is significantly narrower and easier to cross to the west – but of course, this is the Doldrums right now, rather than over the weekend when the fleet will get there.
Image 4 - © Geovoile
So let’s look at Image 5, where we can see the fleet’s position at the current time, overlaid with the weather forecast for almost two days time. The key tactical issue is an area of high pressure in the lee of the Canaries, and just north of the Cape Verde Islands.
Image 5 - © Geovoile
I’ve marked it with a red circle as this forecast only has the breeze in this area down to 11 knots, but many other weather models show it as light as 8 knots in this area. Worse, this high pressure is forecast to drift west across the Atlantic, into the path of the oncoming fleet.
The navigators will have to make a judgement about how best to avoid this light air, while still hitting the sweet spot for the Doldrums. It’s exactly this problem that weather routing software (or are they called apps now?) is designed to solve.
And that’s what you can see (with some help from Jess Sweeney and Explorer) in Image 6, which shows the predicted route (the blue line) for a boat currently in the middle of the fleet sailing through to 06:00 tomorrow morning, 8th November. The bubble of light air is much more visible in this picture, off the coast of the Western Sahara. It shows the boat (the blue triangle) now gybing south from a position at about 27W.
Image 6 - © Jessica Sweeney
If we look at Image 7, the predicted route and position of the boat for 12:00UTC on the 9th November, we can see the boat racing south down the blue line to beat the westward movement of the light air drifting off the African coast.
Image 7 - © Jessica Sweeney
And in Image 8, which shows the boat at 04:00UTC on the 12th November (Sunday) it’s got to about 8S and 30W and is riding the trade winds fast towards the Doldrums, which they should hit later that day.
Image 8 - © Jessica Sweeney
There’s nothing in the routing that suggests anything other than ‘west is best’ for this approach to the Doldrums, with a crossing that looks relatively benign at 30W. This prediction is borne out by recent experience.
In the last race, Abu Dhabi Ocean Racing (with Ian Walker as skipper, and Simon Fisher navigating, now aboard Vestas 11th Hour) hit the Doldrums at 29W and exited first.
It wasn’t the first time Walker had pulled that trick either, doing the same thing with Green Dragon way back in his first race in 2008-09. The old adage ‘never let anyone get west of you into the Doldrums’ doesn’t always hold true, but I think it’s going to count this time around the planet. See you back here early next week to look at how it played out.