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Win or lose: It’s all in the Atlantic
Weather router Bob Rice reveals some global secrets Weather router Bob Rice has been directing skippers to ocean racing success since Phil Weld won the OSTAR in 1980, aboard the trimeran Rogue Wave. He has been routing around-the-world attempts since 1985, with clients including Peter Blake aboard ENZA, Olivier de Kersauson aboard Sport-Elec and lately Steve Fossett aboard Playstation. And don't forget his involvement with Team New Zealand in the last two America's Cup extravaganzas in San Diego and Auckland. In fact, he is down under already, preparing for the next cup with the San Francisco syndicate Oracle Racing. When Rice comments on weather tactics, people listen. Subtle stuff wins races Rice notes that in his extensive experience of routing yachts around the world, races are usually won in the Atlantic, particularly the South Atlantic, where subtle weather conditions can make or break a skipper. Once in the Southern Ocean, the opportunity for gaining ground on a competitor is limited. "But by and large," he explains, "You spend most of your time down there trying to slow the boat down." "Certainly routing decisions need to be made down there, but not the subtle stuff you see in the Atlantic." The North Atlantic From the start at Les Sables d’Olonne, the primary concern for skippers is to escape the jaws of the Bay of Biscay without getting clobbered by a low pressure cell moving in from the west. Once clear of that danger-zone, skippers will try to work their yachts far enough offshore to catch the northerly trades associated with the Azores High without getting caught in the light winds at its centre. Of equal concern is avoiding fluky winds in the lee of the north African coast. Almost immediately, the Vendee Globe sailors will begin analysing where to cross the inter-tropical convergence zone (ITCZ) otherwise known as the doldrums. The Doldrums According to Rice, the ITCZ is best regarded as a climatic feature. There is no way to avoid it. Fortunately for modern sailors, their equipment has improved beyond the imagination of the first adventurers to cross ‘the line’. After all, it took Magellan’s expedition three weeks to get through this fluky zone, where north-east trades meet south-east trades to produce both violent squalls and dreaded calms. Rice notes that satellite imagery helps an awful lot to pick the best crossing point. Too close to the African coast, and the affect of land on the trade winds produces light and fluky air. Too far towards the Brazilian Coast, around Recife, and persistent northerly winds create havoc for skippers on their return leg up the Atlantic. Somewhere in the middle usually results in a good crossing, and regions showing a lot of cloud are regarded as best. It is here where an influx of wind creates enough convergence to produce cloud, so there is a chance that underneath that cloud there is wind right through the ITCZ. Plenty of cloud along this zone also indicates squall activity, and while there is no wind underneath these miniature storms, there is plenty of it all around and careful skippers can leap from one to another, aiding their crossing. Of course, multihulls find it much easier to slingshot off weather systems, but the Open 60s used in the Vendee Globe will also gain from these thunderstorms in the doldrums. At the end of the day, it is luck as much as skill which gets a boat through into the South Atlantic. While routing for Peter Blake’s ENZA, during its record circumnavigation, the 90 foot catamaran never hit the doldrums on its first leg south. The ITCZ was ‘bridged through’ and approaching the line, between 20 and 10 degrees north, the fast cat actually broke a 24 hour distance record of something like 520 miles. Rice's good forecasting continued right across the equator, with ENZA logging more than 500 miles for the day. On the other hand, Olivier de Kersauson’s trimeran Sport-Elec hit an atrocious version of the doldrums on his leg north towards the finish - it is obviously impossible to predict bad doldrums after months at sea. For 24 hours there was no wind above three knots. Despite the lack of wind, the tri managed to log 165 nautical miles, highlighting just how able these mega multihulls are in a variety of conditions. While an Open 60 monohull, with its massive wetted surface will never log a day like Sport-Elec’s, they will manage quite well in the light winds compared to anything else. Rice recall’s the first time he routed for a full circumnavigation. This was in 1985 and his client was Dodge Morgan aboard American Promise, a heavy displacement monohull. The doldrums did its stuff, and the boat logged just 45 to 50 miles a day during the return crossing, despite a good passage southbound. "You have to treat ITCZ as a climate feature," says Rice. "You can try to minimise its impact, but you have little option. Between the African and Brazilian coasts there is a fairly narrow stretch of ocean and there are certain parts in which you can’t go or you will get horribly trapped. You end up with no more than a five to 10 degree slot in which to pass." The South Atlantic This is the ocean that makes or breaks a race leader, according to Rice. If contenders can reduce miles by cutting the corner of the St Helena High and enter the Southern Ocean close to the Cape of Good Hope, they will have set themselves up for the long haul through the wild South. Alternately, on the return leg up the Atlantic, windless high pressure zones off Argentina and northerly winds off Brazil can reduce a winning lead to nothing. Like all oceans except the Indian, the South Atlantic contains sub-tropical high-pressure replacement features. There is a ‘quasi stationary’ high, usually centred over St Helena (thus the name given to it: The St Helena High). A new high moves eastwards, swallows the old one and the St Helena High exists all over again. Rice says that skippers picking their way south between the western edge of the high and low pressure off the South American coast can be tricky, but if a sailor can cut the corner of the St Helena high without running into its windless centre, valuable miles will be saved. This is exactly what Christophe Auguin, Isabelle Autissier and Yves Parlier did in the last Vendee Globe, and by the time they reached the Southern Ocean were well in front of the rest of the fleet. The Southern Ocean While Rice says that races are rarely won and lost in the Southern Ocean, he does not dismiss the place out of hand. Let’s not forget that in the last Vendee Globe, Gerry Roufs was in second place before he disappeared in the most remote corner of the South Pacific. David Adams - winner of Class Two in the 1993/94 BOC solo 'round the world race - gained more than a hundred miles on his nearest rival during one Southern Ocean storm by hand steering through the worst of it. He was better able to react to changing wave - although Adams confesses that he was hand steering to survive, rather than to gain miles. Rice also notes that while routing both ENZA and Sport-Elec in the last two Jules Verne record breaking voyages, there were occasions in the South Pacific where skipper and crew had to make radical moves to get around weather features. The most obvious routing concern is to avoid diving too far south. Skippers do it in the first place because to save distance. The great circle route - the shortest distance between the Cape of Good Hope and Cape Horn - runs south of 60 degrees, deep into the region of drift ice. Fibre and resin composite hulls, whether they use carbon, Kevlar or old-fashioned E-glass, are simply no match for a growler. Weather routers express equal concern when skippers sail south because they risk getting caught on the wrong side of a storm. The constant westerly stream of the Southern Ocean - unlike any ocean on planet earth - is so constant, that winds blowing from the east, especially storm force, will create outrageous cross seas. The violence of a rough sea state pitted against the background swell of the Southern Ocean is best described by Tony Bullimore in his book Saved . He described waves peaking to incredible heights before ‘splitting’, with water running down both the front and back faces. If something like that doesn’t scare the shit out of you … well, you may not be human. Secondly: Skippers racing through the Southern Ocean don’t tend to turn back and run with the wind. They just keep going forward, whatever the cost. So there you have it. Keep to the north. Don’t be stupid. In fact, yachts competing in The Race will have great difficulty getting too far south because race rules demand that yachts sail through New Zealand's Cook Strait. And since the disasters of the 1996/97 Vendee Globe, new way points have been introduced to force skippers north between the Cape of Good Hope and Cape Horn. There is, of course, much more to know about the Southern Ocean. As Rice explains, the typical ‘sequence’ of events is like this: A surge of cold air flows off the Antarctic continent, warms up over the region of ocean where warmer water from the north meets the cold water of the pole (called the polar front) and develops into a low pressure cell. A cold front forms out of the storm, but because weather systems migrate so quickly around the South Pole (there is no land to slow them down), the cold front actually travels ahead of its mother storm, parking itself way out to the east where it redevelops into another low pressure cell, which in turn drags the original storm to meet it and reform again. This all happens so quickly that Rice says the human forecaster has great trouble keeping up with the change in events. In fact, below 40 degrees south, sailors can expect a cold front every three days. "Forecasting in the Southern Ocean is where computer modeling is a revelation," he notes. However, even the most respected models don’t have the data input to recognise certain bizarre features of the wild south - like when cold fronts travel ahead of their parent storm. So Rice, like all good forecasters, uses his extensive historical knowledge to correct wayward computer charts. Source of southern storms There are some predictable storm generation zones around the southern hemisphere, called ‘cyclogenesis’ areas:
Rice explains that air coming off land has a lot to do with it. In the Northern Hemisphere, cyclo-genesis areas exist off the east coast of North America and east of Japan. "In the southern hemisphere there is more water, things move faster," he says. "You always have to keep an eye to the north looking for cyclogenesis areas creating zones of low pressure." "The life cycle of these storms are fairly short. They can go from an open wave to a fully occluded storm in a day or two. In the northern hemisphere, it will take more time to do that. "The life cycle is so short that the wind directions are changing frequently," he says. "You end up with chaotic wind waves developing on top of a 50 or 60 or even 70 foot swell." Rounding the horn With the Southern Ocean behind them, arm-chair sailors might think skippers in the real world can relax after they round The Horn and head north into the Atlantic. While the frequency of extreme sailing might ease - for the fortunate, anyway - tactical decisions of utmost importance lie ahead. This is no time for early celebration. According to Rice, there is a persistence of high pressure east of the Argentine coast, created by the Andes actually shearing weather systems in half. Lower portions of systems traveling from west to east cannot go over these high mountains, but the upper levels can. The result is an area of high pressure in the lee of these mountains at surface level which grows eastward much like a child’s soap bubble grows out of a plastic ring. During the last Whitbread (now called the Volvo ’round the world race), second and third placed yachts in the Auckland to Sao Paulo leg rounded the horn comfortably ahead of boats behind them. All that lead, so carefully preserved in the Southern Ocean, came unstuck when they sailed into the Argentine high and wallowed in near-windless conditions. The afterguard - realising what had happened - literally sailed around the high (remember, winds circulate counter-clockwise around southern high pressure zones) to finish well ahead of their rivals. Auguin, in the last Vendee Globe did the same, and nervously navigated his way north only to run into headwinds, also a feature of the South American coast off Brazil. Fortunately for Auguin, his huge lead remained, in no small part due to gear failure and general carnage among the rest of the fleet. As yachts sail north along the South American coast, they can expect cold fronts over the mountains to spread up into Brazil. Another area to watch for is south and east of Rio, where ex-tropical cloud bands can fester - a stalled ‘long wave’ trough - out of which variable and tricky to predict winds can develop. From Rio north the sea is a router’s nightmare, says Rice, because of the lack of wind. The trades get distorted here thanks to that big, wet and warm swamp called the Amazon basin. Thermal low pressure cells are a feature of the Amazon basin, created by hot land and rising air - or convection. Did you know? The great circle yacht route around the world was pioneered by the quick and slick trading clippers and later by the equally quick yet and larger ‘downeasters’. It was the quickest route home to Europe from Australia and New Zealand. In the last years of sail, grain ships - often owned by Baltic Sea captains and syndicates, sailed out to Adelaide to load grain before returning around the horn. Although if conditions warranted it, captains would sometimes set sail to the west, catching wind circling around the top of southern high pressure cells to drive them westwards past Cape Leeuwin and north into the Indian ocean, where south east trades could be guaranteed. Routing is no routine Routing for the modern multihulls presents totally new challenges for the weatherman, thanks to their remarkable speed. According to Bob Rice, you have to be careful not to let the boat get ahead of your routing plans. "Routers typically look for a six day trend before committing to a tactic and sometimes they fail to realise that these big multihulls can make 2000 miles in four good days." Before they know it, the boat they are routing for is ahead of the plan and the weatherman is caught unprepared. Thermal lows Thermal lows are not restricted to Brazil. Rice notes that they are a feature in Spain and Portugal and the south-western US. More great reading:
Useful sailing sites: www.vendeeglobe.com: The official home page for the Vendee Globe 2000. www.transat2000.com - The official home page for the Quebec to St Malo trans-Atlantic race. www.kenwoodcup.com - the official home page of the biennial Kenwood Cup competition in Hawaii. www.sail-online.com - news and information with a French flair. www.sailingworld.com - news from the publishers of Cruising World and Sailing World magazines. © weather-wise.com 2000 |