Challenging trough

The Volvo Ocean Race fleet appears to be through, but will it catch up with them again?

Thursday December 15th 2011, Author: James Boyd, Location: none selected

Chart above courtesy of Expedition/Tasman Bay Navigation Systems and high res GRIB from PredictWind

The forecast has changed for the Volvo Ocean Race boats over the last 24 hours. Yesterday morning the GFS forecast indicated that the front associated with the depression due south of Cape Town would remain static and the boats would merrily sail away from it and into the northerlies on the west side of the area of high pressure to their southeast. Simple. But now the forecast is indicating that the front is in the process of moving east and dissolving into a trough, with good northerlies to its east, southerlies to its west...and no wind in between.

It appears that the boats first encountered this trough yesterday evening when their speeds were down to around 10 knots. At the latest it seems that all six are now to the east of it, boat speeds remaining a respectible 15 knots for Telefonica and Abu Dhabi in the north, 16 knots for Groupama and Camper in the south and with Sanya the fastest at 0703 UTC at 18 knots.

However the forecast has the trough easing east with the fleet and there seems to be uncertainty of whether it will catch up with them, ensnare them and pass them. Abu Dhabi skipper Ian Walker summed up: “A cold front extending north/south across the fleet containing rain, little wind and a 180 degree wind shift is moving slowly east at about 12 knots. Sadly this means that we sail into it at 20 knots, the wind dies, we stop until the front moves forward and we regain the wind from the old direction.

“All the time this happens, those boats behind pile into the back of us. Only when the front slows down or if we get some magic gust from a rain cloud or something similar will we be able to pop through to the east side and away.

“The only real question for navigators and skippers is where to position yourself on the north/south axis in the line-up. If you can get through it fast then north should be good, if it takes longer then south could be stronger. We are currently trying to slide south a bit to get in touch with PUMA and CAMPER and minimise any leverage they have over us.”

Significant is the north-south divide between the fleet which has increased dramatically since yesterday morning. Then Abu Dhabi was the second last to break from the South African coast and had taken the lead, but Telefonica was the last to turn east and at 1700 moved into pole position. Telefonica's navigator, Andrew Cape, made this same move three years ago when navigating for Puma.

At the latest sched at 0703 Telefonica remains furthest north, some 43 miles to the north of Abu Dhabi. Overnight, not wishing to repeat what happened on leg 1, Camper headed north to converge with the rest of the fleet, however early evening Groupama gybed south and once again appears to be on a flier. At the last sched she was more than 200 miles south of Telefonica. If the forecast is true and the trough overtakes the boats, then Groupama's southerly position may allow her to stay in favourable winds for longer and she will see a shorter transition through the trough, however this comes at the high price of sailing further and further away from the great circle north and will leave them in a slow point of sail once they do get back into the west side of the high. But going on another flier following what happened on leg one - is that sensible?

This morning Franck Cammas reported: "There is a possibility to cross the front in the north tomorrow night, and we are trying to reduce the gap to cross it with the others.

"Our idea at first was to go south, we had a long term strategy there. We worked on that for the past 2 or 3 days. The other ones have been more pragmatic and stayed in the middle. Now, to try to cross with the other ones tomorrow night, we have decided to get closer from the fleet. It was a tough and unpleasant decision. But at some point you need to limit the risk and not to lock yourself in an option, which was good at first and is now not as relevant because of this opening in the north. We are all on a same longitude so everyone will in a funnel to cross that very small hole. It will be a new start Saturday morning.”

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