Leg Info

Leg starts on:
5 November 2017

The basics:

This one is a 7,000 nm run south, starting from Lisbon on 5 November, and going from the coast of Portugal to Cape Town at the southern tip of the mighty African continent. It’s a classic north to south Atlantic run, passing through multiple Climate Zones.

Err... what’s a climate zone?

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. When they race from north to south, the fleet is constantly crossing from one band of climate to another – the trick is finding the right entry and exit points for each transition, a moment when conditions can radically change and gains and losses can be spectacular.

What are the challenges? 

Subtropical High Pressure Zone (Horse Latitudes): Let’s not be so negative, a challenge is also an opportunity, and there are many opportunities to make gains on this leg. The first is a little thing called the Azores High – a Sub-Tropical High Pressure Zone named after the island chain. 

This is the first climate zone the fleet will encounter, sitting around 30-38 degrees, these are huge areas of stable, semi-static high pressure. Also called the Horse Latitudes, so named because the light winds associated with these areas of high pressure slowed up the old sailing ships so much that they would run out of water and be forced to throw the dying horses overboard. Or so they say.

Trade Winds: The Azores High also determines the position of the second oceanic climate zone, the Trade Winds. These are 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 from a Sub-Tropical High Pressure Zone towards the equator.

Depending on the position of the Azores High, the fleet could pick up the Trade Winds off the start in Lisbon and ride them all the way south – fast, fun sailing in glorious conditions. But if the high pressure is sitting over Lisbon, the fleet will find themselves struggling for speed in the light winds. In this case the race will be on to reach the Trade Winds first – slow, stressful and no fun at all, unless you’re winning.

Island Chains: The Canary Islands and the Cape Verde Islands both lie in the way as they head south – these are both volcanic, high pieces of land, and they can impact the strength and direction of the wind for hundreds of miles. And that means lots of overtaking opportunities.

The Doldrums (ITCZ): South of the trade winds lie 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 – all-in-all  a  nail-bitingly high level of unpredictability.

Incidentally, for the weather nerds, it’s the cooler air from the north and south of the Doldrums that is sucked in to replace this rising air, and this helps form the north-easterly Trade Winds of the northern hemisphere, and the south-easterly Trade Winds of the southern hemisphere.

A good Doldrums crossing can win this leg, and a bad one can lose it for you. So this will be a tense time. The key is picking the thinnest point to cross and usually that’s more to the west, so the boats will head that way until they pick their spot, and then turn south to go for it. Legend has it – and the legends run deep on this one, back to the days of clipper ships – that the sweet spot is around 27-28W, but anything between 25W and 30W can work. 

St Helena High: The thing about the climate zones is that they are mirrored north to south about the Equator. So the Azores High has a mirror sister sitting in the South Atlantic, sometimes called the St Helena High for the island. High Pressure means light wind and so it blocks the direct route to Cape Town.

The teams will probably go to the west of the centre of the high, and try to work their way down this side. It’s almost always quicker to head south, around the centre of the high, to get into the final climate zone, which we’ll call the Westerly Storm Track.

The Southern Ocean and the Westerly Storm Track: In the Westerly Storm Track, storms and low pressure systems swirl west-to-east around the globe. They circulate the Arctic in the north and the Antarctic in the south, always moving west to east. The strategy is always to get clear of the Sub-Tropical High Pressure, and into the Storm Track, find a low pressure system moving east and ride with it. It will accelerate a boat east across the South Atlantic, often taking them into the Southern Ocean, and sometimes take them right into Table Bay. First to become a rider of the storm will usually win it.

Lots of opportunities, must have meant some big winners?

Oh yes, in 1997-98 race- newbie Paul Cayard and his navigator Mark Rudiger boldly split from the fleet to lead EF Language south from Fernando de Noronha. The move got them into the Westerly Storm Track first, they picked up a ride and it gave them a lead that they never relinquished, going on to win the race. Sweet.

 

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