Leg 9 Strategic Review Part 2 – Into the unknown

Team Brunel and team AkzoNobel lead the fleet after handing out a lesson in heavy weather sailing. With less than 1000 miles to go, Mark Chisnell peers into an uncertain future...

May 25, 2018 20:00 UTC

Text by Mark Chisnell

The North Atlantic has thrown everything at the fleet – up to and including the kitchen sink – in the last six days. The race from Newport to Cardiff for double-points on Leg 9 has already been one of the most dramatic, with the fleet spread 250 miles apart across the race course as early as Day 2.

They’ve dealt with a cold front, a fast moving high pressure, and then got hammered by another low pressure as they all came back together at the Ice Exclusion Zone. And now, after teaching everyone a lesson in heavy weather sailing, Team Brunel and Team AkzoNobel lead the fleet with less than a thousand miles to go... and into a very uncertain future.

Storm track

We said that this leg would be raced mostly in the Westerly Storm Track, and right now it feels like it with records falling like leaves in autumn. The Storm Track is the high latitude region where storms and low pressure systems swirl west-to-east around the globe.

It no longer looks like the race will finish in the Storm Track though, as the current situation and the forecast show that the Storm Track’s southern neighbor, the Subtropical High Pressure Zone (a stable, semi-static area of High Pressure usually lying between 30 and 38 degrees) will be far enough north to block the route to the finish in Wales (more on the climate background in the Leg 9 Preview.

The set-up

We left the fleet on Tuesday 22nd May at the end of the last Strategic Review with the fleet split into two groups, as we can see in Image 1 from 11:00UTC on the 22nd May.

©Geovoile - Image 1 (Click for larger image)

The leaders were all in the south, Team Brunel (yellow), Team AkzoNobel (purple) and Vestas 11th Hour Racing (orange) were still sailing fast downwind speeds, thanks to a south-westerly wind from a cold front that they had picked up not long after leaving Newport. But at some point, they would have to gybe and head north-east, as the cold front was headed for West Africa before finally stalling in mid-Atlantic.

Team Sun Hung Kai / Scallywag (grey) had already bitten the bullet and gybed a couple of times to allow the cold front to pass. They were now sailing upwind in the light northerly breeze behind it.

The northern group – Dongfeng Race Team (red), MAPFRE (white) and Turn the Tide on Plastic (light blue) – had had a tough time over the previous night. They had gybed away to cross behind the cold front much earlier, and had been struggling with the light northerly winds they found behind it. This looked to get even worse in the short term, as the main region of high pressure was forecast to pass over them in the next 24 hours.

The big gybe

Vestas 11th Hour Racing and Team AkzoNobel were the next to gybe out of the south, just after 14:00UTC on the 22nd May. They came across towards Team Brunel who elected to gybe and head north with them as we can see in Image 2 from 16:00UTC on the 22nd May.

©Geovoile - Image 2 (Click for larger image)

Meanwhile the high was closing down on the northern group as forecast. They were once again back in light winds around 7-10 knots, as was Scallywag to their south. Everyone was going to have to deal with this high pressure system to get to the new wind, a low pressure system arriving from the west on the 24th May.

The south stays strong

The breeze started to shift for the southern group around 17:00UTC on the 22nd May, as they broke through the cold front. In Image 3 from 20:00UTC on the 22nd May we can see that the whole fleet now has a roughly northerly wind. The big difference is in the wind speed. The southern group still have 15-18 knots, while the northern group are now at ‘Peak Pain’ as the high rolls right over the top of them. Team Brunel’s lead over Dongfeng Race Team is up to 45nm.

©Geovoile - Image 3 (Click for larger image)

The south goes sour

It finally started to go sour for the southern group overnight into the 23rd May. If we look at Image 4 from 03:00UTC on the 23rd May we can see that the high pressure has got much more organized, centered around a point to the east of the northern group.

©Geovoile - Image 4 (Click for larger image)

This has left the southern group in the southern sector of the high pressure, in an easterly wind. They are ploughing slowly upwind on starboard tack, waiting for the high to move further east so they can get into the south-easterly and eventually the southerly winds on its western side.

The northern group are already there – they are all west of the high pressure, in the south-easterly breeze and rolling along at 13-15 knots of boat speed. They can now settle into a steady reach towards the EZ, on a trajectory that will take them into the path of the next low pressure. It was payback time for the northern boats.

Not for long

By midday UTC on the 23rd May (Image 5), the leaderboard said that Dongfeng Race Team had almost drawn level with Team Brunel – just 3.6 miles between them. This was about as close as they got though, because the high was still moving. Both groups of boats now had virtually the same wind angle – despite sailing very different courses to converge on the EZ.

©Geovoile - Image 5 (Click for larger image)

How was this possible? It was because of their different positions relative to the centre of the high. The northern boats were in the southerly at 9 o’clock relative to the centre, while the southern group were in the south-easterly at 7.30 relative to the centre. It gave them the same wind angle and the same wind speed, and that usually means the same boat speed, and so the southern boats stopped bleeding miles.

The only significant difference in their conditions was that the two most westerly boats in the northern group had a bit more wind speed – 19-20 knots rather than 15-16 knots (we can see this in the table at the bottom of Image 5). This was the first sign that the new low pressure was approaching.

Convergence

The fleet continued to converge through the night of the 23rd and into the 24th May – both groups straight-lining, neck and neck and blasting right at the Ice Exclusion Zone. If we look at Image 6 from 07:30UTC on the 24th May we can see that they reached the corner of the EZ just before the chasing cold front reached them.

©Geovoile - Image 6 (Click for larger image)

I think the leaderboard calculations altered here as they passed this waypoint. Dongfeng Race Team were just a couple of miles behind at 20:30UTC on the 23rd, and closer to 50 miles behind by 04:00UTC on the morning of the 24th. There was no obvious change in the bearing between the boats, and at this point the losses stabilized. In Image 6 we can see that Dongfeng were now 47nm behind Team Brunel who were still leading the southern group.

More wind

The northern group of boats still had more wind – 28-30 knots versus 22-24knots for the leading pack of three in the south; but they were now almost in the same piece of water, and they all had the same wind direction (around 160-170 degrees). So the northern group were now sailing a narrower wind angle (around a 105 degrees) than the southern group (around 125 degrees).

In that much breeze, I think the slightly wider wind angle of the southern group should probably have been faster on average (although it’s noticeable that all three recorded speeds for the southern boats in the Image 6 data table are quicker than the northern boats). It will depend on the wave state, and the crew’s individual ability to squeeze what they can out of their sail inventory and set-up.

Done deal

It certainly appeared to play out in favour of the south and by 14:30UTC yesterday afternoon, 24th May (Image 7) it was a done deal. Once the leverage was gone (the separation of the boats perpendicular to the course) the play had closed out. We can see in Image 7 that the southern group were now directly between the northern group and the rhumb line (white dashed line) to Cardiff. They could chalk up a win for the biggest split and biggest strategic move of the race with a lead of about 50nm. Nice work.

©Geovoile - Image 7 (Click for larger image)

Conditions were pretty wild at this stage with 26-35 knots recorded across the fleet. There was a good chance of a 24-hour record with a boost from the Gulf Stream and flat water left behind by the high pressure. The records duly tumbled. Team AkzoNobel moved into the lead with a phenomenal run overnight into the 25th May that topped out at 588nm in 24 hours – an improvement of nearly 40 miles on the best run in the previous race.

Ride the low

Team AkzoNobel got the lead and the record overnight, and in Image 8 from 09:00UTC today, 25th May, we can see the fleet still cranking the miles down as they head for Cardiff. Conditions have moderated a little as the low had started to stall, and the fleet have moved ahead of the cold front.

©Geovoile - Image 8 (Click for larger image)

The reason the low’s going to stall is the big blocking high pressure that’s made itself at home in the North Sea between Scotland and Scandinavia. This high will dominate the final stages of the race – as we will see in a moment.

If we bring it up to date at the time of writing in Image 9 from 13:00UTC today, 25th May, we can see the fleet ahead of the cold front, with the big low pressure system centred to their north-west.

Team AkzoNobel still leads Team Brunel, the margin just under nine nautical miles at this point. These two have done a fine job in these high speed conditions, working out a lead of over fifty miles from third placed Vestas 11th Hour Racing and sixty miles to fourth placed Dongfeng Race Team. The overall leader MAPFRE has plenty of work to do, now almost a hundred miles behind the leader. However, conditions might just work in favour of another comeback...

Set up for the high

It looks like another very tricky finish in Cardiff, echoing the one in Newport. Cardiff is at the top of the Bristol Channel, which has strong tides, a lot stronger than Newport. And it doesn’t look like there will be much wind again...

If we look ahead in Image 10 with the weather and the predicted positions for the fleet at 14:00UTC on the 26th May – a little over 24 hours' time – we can see that the ride has come to a crashing halt. The fleet will run smack into the ridge of high pressure, stretching down from the North Sea and Scandinavia.

They will have to cross this wall of light air to get to the finish, and they will be spending a lot of time thinking about that right now, as they have speed and power and can choose (to a degree) where and how to approach the high to best cross it, but...

A moving target

The wall is going to move with them. If we look at Image 11 from 07:00UTC on the 27th May we can see that the high pressure ridge will get pushed east by the next incoming low, tracking with the fleet towards the British Isles.

And for a while, as we can see in Image 12 from midday UTC on the 27th May, the low might even catch up with the fleet and provide them with a little nudge towards the coast – towards is the operative word here, it’s not going to get them all the way. The high pressure will continue to dominate over Britain in general and Cardiff in particular through to the finish.

Irish Sea bog

If we look at Image 13 from midday UTC on the 28th May we can see that the fleet are in for a very slow and challenging crossing of the Irish Sea early next week. And that will persist through Tuesday, as we can see in Image 14 from 14:00 on the 29th – there’s not going to be much breeze to get them home.

There’s also going to be a lot of local effects to deal with as they sail around the bottom of Ireland, then approach south-west Wales and head up the Bristol Channel. I’ve said already that this is a very tidal area, but it’s also an area with complex sea breeze development – with more than one shore to choose from if you’re looking for a thermal breeze.

Percentage play

The question is how to approach this very dynamic situation? Every time I’ve run these predictions through to the finish I get a different answer for how it’s going to play out. I really wouldn’t want to be making big strategic bets on the basis of these forecasts. In this situation you can do a lot worse than simply sail at whatever angle takes you towards the finish line fastest at any given moment. It doesn’t always work, but it’s often the percentage play when the forecast is changing with every iteration.

It’s going to be fascinating to watch all the way to the finish, and with double-points on this leg, no one out there needs to be reminded that there is a huge amount at stake.