A variety of conditions will test navigators and crews right from the very start. As the teams put the final touches to their yachts the meteorologists will continue to study the weather patterns right up to the last minute.
Although favourable winds are expected for the start these will change early next week. The weather at the moment is rather unusual with low pressure all around the UK and a ridge of high pressure over it. This will swing the winds to the East or Northeast with mainly sunny skies, although a small low over Europe could give the chance of an occasional shower.
On Sunday the crews should enjoy light East to Northeast winds to help them out of The Solent. A building ebb tide taking the yachts to the west, combined with a downwind spinnaker start, will make it difficult to time the approach to the start line perfectly. Too early will bring the embarrassment of a penalty right at the beginning of the race, but nobody wants to be the last out of the Solent. For spectators ashore and afloat it should be a pleasant day that may start a little murky. This should soon clear giving some sunshine as the temperature rises to about 17 Celsius.
The main generator for the Easterly wind is a depression in Southern Biscay; this is slowly moving to the east and filling as it drifts away over France. The winds to the Northwest of it will gradually weaken becoming light and variable through the English Channel on Monday morning. Once the fleet is clear of the Needles, about 13 miles from the start, and heading for the Northwest tip of France 180 miles away, they should have a fast trip with 10-15 knots of wind (force 3 to 4) first few hours. The wind is then likely to drop and become variable as they approach the French coast.
Ex-tropical storm Gabrielle will start to make its presence felt as it moves eastwards. Although it has lost its tropical status there is still a lot of energy in the system which is likely to bring strong Southwesterly winds through the Bay of Biscay on Tuesday.
Monday will therefore be a day of transition as the mainly Easterly winds drop and swing around to the Southwest before increasing. This will give the tacticians their first big dilemma of the race; whether to try and keep in the lighter more favourable winds and risk becoming becalmed near the coast of France, or to attempt to head west to meet the stronger headwinds.
Also added to this equation are the strong tidal currents found close to the French coast and around the island of Ushant. The lighter the wind, the greater the tidal effect has on progress, either helping the yachts along or slowing them down. Timing any approach to the coast and the stronger tides will be crucial to maximising gains but it is difficult to do in a shifting wind pattern.