As the competitors reach the entrance to the Atlantic they will be confronted with one of three possible scenarios:

A series of low-pressure troughs will bring winds which switch between the south-west and the north-west.

If that happens the yachts can effectively drop down in steps to the Azores with a tack each time the wind direction shifts.

The second possibility is an extension of the Azores anticyclone towards France which would mean skippers having to skirt along the top of a ridge of low pressure for a large part of the crossing or opt for a safer but much longer route.

Finally, the third - and most unlikely - possibility is that a powerful anticyclone settles over England, creating an easterly wind virtually as far as the Azores. Strategies would then be much simpler as crews would just have to head straight for the Azores as quickly as possible.

>> More Challenge Mondial information from the BBC Weather Centre