She's now three days ahead but the massive high in Ellen MacArthur's path could change things dramatically over the next couple of days

Every minute of Ellen MacArthur’s current 3 day 10 hour lead is going to be needed to soak up the losses as she sails into the high pressure tomorrow.

The breeze will stay from the south-east today but Commanders expect lulls down to 15 knots and gusts up to 28 knots through to midnight tonight.

The wind will start to diminish in the early hours of tomorrow as B&Q gets closer to the ridge of high pressure, bringing a very slow period from tomorrow afternoon through Friday. There is no avoiding the high pressure – it is too big, with the ridge axis from NE-SW stretching across MacArthur’s pass – and the million dollar question is how quickly B&Q can cross the ridge to get to the other side and into more breeze.

If and when she gets across, MacArthur faces an upwind battle to the finish line.

Chatting from the boat MacArthur said: “I don’t know whether to change up to the Solent or not [now on 2 reefs and smaller staysail], it’s right on the limit in the gusts but I’ve only got 18 knots right now. I need to be going faster, but the sail change takes me so long now that I’m tired. And I don’t want to risk breaking the Solent.

“The problem is that we have to make more gains now, as the weather looks terrible ahead. Current routing shows me in late Tuesday, and the trend is getting worse. Now is the only time to make gains. Sail changes taking my twice the time they were earlier in the trip.”

MacArthur has less than 1,500 miles to go on the direct route and VMG required to break the record has dropped another notch to 8.4 knots. MacArthur cannot sail the direct route [approximately 30 degrees to the finish of Ushant right now] as her course is dictated by the current weather and negotiating the weather system ahead.

In upwind conditions boatspeed maximum is about 14 knots if the sea state allows it, and of course in that situation heading is unlikely to be on the direct route, so VMG could be less than 9 knots. This is why every mile of gain now might be needed, with a forecast of light winds followed by upwind conditions.

To break Francis Joyon’s current record MacArthur must cross the Ushant finish line before 07:04 on Wednesday 9 February.