Volvo Ocean Race- Knut Frostad explains the Doldrums
by Knut Frostad, Volvo Ocean Race on 16 Nov 2011
With the first boats preparing to cross the dreaded Doldrums from around midnight on Monday, we take a look at this notorious area of the ocean, with the help of someone who has negotiated them more times than he cares to remember, Volvo Ocean Race CEO Knut Frostad.
Huge clouds approach Ericsson 4, in the Doldrums, on leg 5 of the Volvo Ocean Race
Guy Salter/Ericsson 4/Volvo Ocean Race © http://www.volvoceanrace.org
born Frostad is a double Olympian and has sailed four Volvo Ocean Races, two of these as skipper. Here he gives some background on the Doldrums, which were the bane of sailors for many centuries, but are now more of a hurdle to be overcome as quickly as possible by the current generation of round the world sailors.
What are the Doldrums?
The Doldrums are a large-scale weather system located on and around the Equator. They are best known as an area of very light winds which can slow sailing boats to a virtual stop, but the Doldrums can often also produce violent thunderstorms and sudden fierce squalls.
Transient in nature, the Doldrums can quickly change shape and location and are therefore difficult to predict. The Doldrums are sometimes called the Intertropical Convergence Zone or the Equatorial Convergence Zone.
Where are they?
In the Atlantic Ocean, changes to the Doldrums latitude are mainly due to seasonal effects. In summertime in the northern hemisphere they can appear at 10 degrees north, while in winter time they normally lie at four degrees north.
The width of the Doldrums varies with longitude, being wider at their eastern end due to the northern and southern hemisphere trades meeting more head on there, and getting narrower close to the Brazil coast where the trades are more tangential than frontal.
How are they created?
Primarily, the Doldrums are caused by the convergence of two sets of Trade Winds which blow towards the equator from the north and south poles respectively.
Combined with the warming effects of the equatorial sun, this convergence causes the air to move vertically rather than horizontally, resulting in little or no wind on the ocean surface.
So why do racing sailors dread them?
To a large degree, negotiating the Doldrums involves luck rather than navigational strategy – which is why yacht racers dread them. Many a big lead has been eaten up or lost completely in previous editions of the Volvo Ocean Race.
Knut sums up the random nature of the Doldrums like this:
'Anything can happen in the Doldrums. It depends on the day and it can have a lot to do with luck. The Doldrums can give you cards to play with or no cards at all. Before the teams reach the Doldrums they can think about strategically where they want to be, but once they get there they have no more choices and they are stuck with what they have. It’s a difficult area to predict and the weather models don’t work in the Doldrums because there is no gradient wind, just localised effects.'
Where is the best place to cross them?
In the Atlantic they are generally thinner the further west you choose to cross them but there are no guarantees with the Doldrums, as Knut notes:
'It could be that the Doldrums expand right where PUMA, Telefónica and CAMPER are crossing leaving no Doldrums for Groupama. This has happened many times in the past. The opposite could also happen where the leaders get nice winds all the way through and when Groupama arrive there is a big bubble with no way of escape.'
Could the boats stop for days like in the old days?
Volvo Open 70s are the fastest monohulls in the world and with their huge rigs can cope with light winds better than previous designs like the maxi yachts and even the Volvo Ocean 60s, as Knut explains:
'In the old days when we had heavy boats you would get a puff of wind and the boat wouldn’t move. The big difference now is that these boats don’t need very much wind to move and so they don’t really park up. Now, one puff of wind would get these boats moving. In two knots of wind they will do four knots of boat speed because a Volvo Open 70 generates its own wind. So it’s unlikely that they park up for a long time.'
How are the Doldrums likely to affect the Volvo Ocean Race fleet?
The crews will have to be fully alert to try to spot patches of wind to keep them going and also to avoid being caught in a sudden wind squall with their large light wind sails up. Crossing the Doldrums in darkness will not make this task any easier.
The main priority will be to avoid letting their boats stop completely as overcoming the hull’s inertia to get moving again requires a significant increase in wind strength and could leave then stranded for hours. Any direction, even back the way they came is OK as long as they are moving.
What is the fastest way to get through the Doldrums?
Instead of big picture climatic strategy the crews will need to focus on a series of short-term weather tactics. In the Doldrums, most wind comes from the downdraft from large cumulonimbus clouds and the crews will have to pinball from could to cloud, sailing close to their edges where the strongest breezes lie.
Rainclouds however, produce holes in the breeze and are to be avoided at all costs.
Often the best way to predict how things will evolve is to keep track of the clouds using a handheld compass and try to figure out whether they will bring rain or not.
Could Leg 1 be won and lost in the Doldrums?
Knut believes it is definitely a crucial point in the leg and one the skippers and navigators in particular will be dreading.
'It’s scary for the teams because it’s one of the only times they have absolutely no control over their destiny. They can forget about weather data or routing. Their radar can be a big help but they also have to go on what they can see outside. The vertical air movements mean there’s a lot of clouds and it can rain like crazy. Around these clouds there’s wind. It’s going to be a very tense time for then all.'
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