EDS Atlantic Challenge - leg 3 preview

madforsailing talks to meteorologist and Gartmore crew Gilles Chiorri about the transatlantic leg from Portsmouth to Baltimore

Leg three of the EDS Atlantic Challenge starts tomorrow off Portsmouth Harbour at 1730. The start is on line forming a transit between Southsea Castle and the outer distance marker and the boats will head west down through the Solent leaving Prince Consort and Gurnard buoys to port. Here French meteologist Gilles Chiorri of MeteoConsult (and who has been sailing on Gartmore for the first two legs of the race) gives his predictions for what will happen in leg three:

"It is too early in the race to play tactics," says Chiorri. "You still need to make your own race." The EDS is said to stand for 'except downwind sailing' as the first two legs have been on the wind and this looks like it will not change for the third leg across the Atlantic.

At this time of year the Azores high pressure system is fully formed with a series of depressions that pass over the top of it. But in the early stages of the race, the reach of the Azores high will be so large it extends north to Iceland, effectively blocking their path.

For the first two days as the boats head west down the Channel, the boats will experience relatively light (10 knot) west or north westerly winds combined with the added effects of any sea breeze. Chiorri believes that most boats will head out of the Channel south west on starboard tack.

As the high receeds south a low pressure system will head slowly east across the north Atlantic and will park at around 25degW 58degN. The trough preceeding this depression will also stop and the boats will have to sail towards this to benefit from stronger winds and will tack onto port as they pass through the trough and the wind backs to the south west.

The predominant feature for the competitors in the middle of next week will be the Azores high pressure system and a technique used is to head in towards a point to the north of the centre of the high on starboard in north westerly winds and tack out again once this point is reached and the wind goes back to the south west.

Beyond this there seems to be a big hole in the weather forecasts at present. Chiorri says the area to the north west of the Azores high pressure system is to be avoided as there is no wind there.

The polars of the boats will also play a crutial role in the decisions skippers make. Kingfisher and Sill have proved to be substantially better than the older boats going to windward and this gives their navigators more options. However because the older boats know that the expected conditions on this leg will be unfavourable to them this may encourage one of the skippers - the Italians perhaps? - to take a flier and go on what OSTAR competitors call 'the southerly route', to the south of the Azores high. This technique is extremely risky as it involves sailing many many more miles, albeit in favourable winds.