9:22 PM Tue 17 Mar 2009 GMT
There are some interesting options facing the Volvo Ocean Race navigators, tacticians skippers and fans as the race leaders head up the South American coast.
A patch of strong wind off Tierra del Fuego and the Falkland Islands backed by ab area of light winds has the routing and optimisation software urging the yachts to take an offshore course to stay with the strong tailwinds and veer well offshore rather than sailing the more direct route to the finish line in Rio de Janiero, Brazil.
The charts below show the leading competitors at 0400hrs NZT and then three hours later with the wind shading active to show the effect of the weather systems, red indicates strong wind and mauve even stronger winds. The direction and strength is highly favourable to the Volvo 70, making the deviation from the Great Circle Route very attractive.
A shot 24 hours later projects a relatively minor course change for race leader Ericsson 3, while at this stage the PredictWind and Expedition software suggest that the other three yachts should be looking at a big right hand turn to the east to take maximum advantage of the strong weather system.
24 hours later again the reason for the deviation becomes clear as both Ericsson 3 and Ericsson 4 try to skirt around a patch of light air which would give them reaching conditions in just 10kts, while by staying with the increased pressure Ericsson 4 would enjoy fast reaching conditions of 25-30kts with gusts up to 20% on top of that average - hitting 40kts plus.
A further 24 hours down the route, the method in their madness becomes apparent, as the boats close together laterally on the water and this trend continues as the head for the Rio, and get closer to the Brazilian coast.
The effect of the initial deviation becomes clear as the routing and weather software are recommending that the faster course is for the yachts take a bite to the east initially before sailing a more direct northerly course, rather than the Great Circle Route which would just have them sailing a north easterly course through some very light airs and slow sailing conditions.
However with the weather data not at its most reliable in remote parts of the planet (due to the relative lack of observation points) these prognoses could change as the weather data is updated, and certainly it is a big call to move east so early in the leg. But on the other hand, that might pay big dividends.
Everyone knows the questions - the answers are a little more difficult.
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How to read these images
The boats have four digit codes as follows: ERT3 - Ericsson 3; ERT4 - Ericsson 4; GDRA - Green Dragon; ILMO - PUMA Racing; TELA - Telefonica Blue;
The wind is shown in barbed arrow format. The longer line is the wind direction, if it has one longer barb at right angles to the tail, then the wind strength is 10 kts, if there is a half size barb, further up the shaft then the strength is 15kts, two full size barbs indicate 20kts and so on.
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The images used in this story have been generated by Expeditionwhich is a tactical and navigation software application which has been developed by veteran Volvo Ocean Race navigator and Whitbread winner, physicist Nick White, initially for his use in the 2001-2 Volvo Ocean Race with Team News Corp and the Stars & Stripes Americas Cup team.
Since then, Expeditionhas been continually refined by a core group of world-renowned navigators and two-time America's Cup winning navigator Peter Isler has consulted closely in the development of the system. Expedition supports more instrument systems, is easier to use and has the most powerful and useful functions for the racing navigator.
Expedition is now has PredictWind integrated into the application as an option for PredictWind subscribers.
The wind data and prognosis used to produce these images also uses software developed by PredictWind, an application developed by Jon Bilger a top NZ youth and Olympic sailor who turned his hand to wind and weather prediction, and helped Alinghi to their outstanding victories in the last two America's Cups.
Now that same technology is available to the weekend sailing and club racers, the cruising fraternity or professional sailors around the world. Select any region in the world of interest to you and PredictWindwill monitor the area for you and provide updated predictions on demand.
PredictWind is a subscription system, with a number of options. While some may feel the wind is free, the ability to get a five day detailed wind forecast for an area of interest creates great peace of mind, allowing forward planning and decision making to be made with some certainty. The time and money saved through being able to work with a high degree of confidence, is more than offset by the relatively small cost of the subscription.
But don't take our word for it, get PredictWindnow and have a 30 day trial for free, and see for yourself.
by Richard Gladwell, Sail-World.com
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