Leg 6 Strategic Review Part 2 – It’s not normally like this here…
Leg 6 Strategic Review Part 2 – It’s not normally like this here…
It’s not even a week since the start of Leg 6 and we have already seen two dramatic splits in the fleet as team AkzoNobel and Team Sun Hung Kai / Scallywag first took a position to the north of the fleet, then swopped sides to set-up to the south.
The wheel is still spinning and the ball still bouncing as the fleet converge, but right now it’s looking like the second half of their strategy has worked and they will hold a lead into the Doldrums.
Climate Zones again
I’d better add my usual disclaimer – that these strategic reviews rely heavily on the idea of Climate Zones. The Leg 6 Preview provides the full story, but briefly, just know that the earth’s oceanic climate features distinct bands, lying horizontally and looping the globe, running out from the Equator to the Poles in a mirror image.
When the fleet races from north to south (or vice versa) as they are right now, then they will cross through several of these climate zones and the transitions from one type of weather or climate zone to the next becomes a critical feature of the strategic game.
Not normally like this here…
So much for the theory – as we saw in the first strategic review for Leg 6, the weather is far from normal and it looks like it’s going to stay like that all the way to the North Island of New Zealand. This leg is turning out to be more about managing the boat’s position relative to the movement of big weather systems, than it is about the transition from one climate zone to another. It’s more like racing west to east in the storm track than racing north to south through the trade winds and the Doldrums. Go figure.
When we left the fleet on Friday 9th February they were headed north-east on a long detour out into the Pacific to avoid the twin peaks of the first hazard. One was the exclusion zone that had been put in place by race officials to keep them away from a cyclone. The second was a huge area of high pressure and light winds that was developing on the straight-line route to Auckland.
I called this detour into the North Pacific the ‘easterly variation’ as it had been used successfully (as opposed to the straight-line route) in past races. This time around – with the whole fleet taking the easterly variation – it was more a question of timing, and how far north and east to go.
The answer to that question lay in the movement of a low pressure system that was building to the north of the fleet. It was forecast to move east. It did just that and the weather from this system has dominated the past four days and given the leaderboard its current shape.
Let’s start with Image 1 from 13:00UTC on 9th February. The fleet was split in two – Team AkzoNobel (purple) and Team Sun Hung Kai / Scallywag (grey) were to the north, while Team Brunel (yellow), Dongfeng Race Team (red), MAPFRE (white) and Turn the Tide on Plastic (light blue) were to the south. The low pressure system was clearly visible spinning up in the top left corner of the image, to the north of the fleet.
Geovoile – Image 1 (click for larger image)
In Image 2, from 01:30UTC on the 10th February we can see that the low had moved quickly east. The front was stretched out to the south-west of the centre of the low, and had already caught Team AkzoNobel and the Scallywags. The south-easterly wind was easing for everyone, ahead of the change from the front.
Geovoile – Image 2 (click for larger image)
The front arrives
In Image 3 from 10:30UTC on the 10th February we can see that the front had now passed over the two westerly boats. They were both in the strong northerly wind behind the front (they had almost 20 knots wind speed in the table, compared to just 8-10 for the eastern group) and were about ready to hit the accelerator pedal, and track south-east with the weather system.
Geovoile – Image 3 (click for larger image)
The eastern group were stuck ahead of the front in a light southerly wind, and they had little option but to carry on going east, and wait for the front to reach them. I guess they could have tacked and headed back towards it, but I’m not sure it would have changed the outcome.
In the previous Strategic Review we anticipated all this happening about ten hours later, in the evening (UTC) of the 10th February. We also expected the breakaway pair to have kept pace with the rest of the fleet, and to be positioned to the north or north-west of them; instead of which the losses they took in the light winds around the Japanese islands left them almost due west of the other four boats.
Targeting the front
Despite all this, Team AkzoNobel and Team Sun Hung Kai / Scallywag still got the outcome they were looking for – they got to the northerly wind behind the front first. This was their original goal right back when they made their initial tack to the north-east at the southern tip of Taiwan.
They committed early, and they committed hard to try and reach the front first. So it seems only fair that after the rollercoaster ride of light winds and the unpredictable movement of the low, they were still almost perfectly positioned to pick up the weather system before the rest of the fleet.
It plays out
In Image 4 from 18:00UTC on the 10th February, we can see this playing out. Team AkzoNobel and Scallywag were both tracking behind the front in the 20knot northerly, with Scallywag taking the more southerly course of the pair. The rest of the fleet are right in the messy transition of the front, with a light westerly wind, and they had to wait for the front to pass over them.
Geovoile – Image 4 (click for larger image)
All good things come to those who wait, and eventually the front rolled over the remaining four boats and everyone got going in a very solid northerly wind. Fast forward 24 hours to Image 5 from 18:00UTC on the 11th February and we see that at this point, it does look like the eastern group will do better out of all this…
Geovoile – Image 5 (click for larger image)
Not so fast, the ball is still bouncing, the wheel still spinning…
Still lots of leverage
The leverage might be reducing, but there was still 150nm of east to west separation – and don’t forget that the forecast in the last strategic review was for the front to stall again in front of them, forcing them to cross it a second time to break through into the trade winds, with the band of light winds between the front and the trade winds looking narrower to the west…
Check out Image 6 from 08:00UTC on the 12th February for the moment when it started to look a whole lot better for the westerly boats. In the east, Team Brunel, Dongfeng Race Team and MAPFRE had all over-run the front and had a five knot breeze from a ‘variable’ direction. Turn the Tide on Plastic had managed to hold the strong northerly wind a bit longer and had used it to pass the others.
Geovoile – Image 6 (click for larger image)
Meanwhile, out to the west Team AkzoNobel and Scallywag still had 16-18 knots from the north, and they were sliding right by everyone else on the inside of the turn.
Turning the screw
Six and a half hours later, in Image 7 from 14:30UTC on the 12th February we can see the pain really developing for the eastern group. They were stuck in the bubble of light air ahead of the front, while to the west, Team Sun Hung Kai / Scallywag had cruised through a much narrower band of light air with minimal disruption to service – they now had 13 knots of north-easterly and the trade winds (the east-northeasterly wind in the bottom right of the picture) were within reach.
Geovoile – Image 7 (click for larger image)
Fortunately for the eastern group, the light air was moving east with the front, and released them much more quickly than if they had had to sail their way clear. In Image 8 from 19:30UTC on the 12th February, we can see that almost everyone was now out of the light air, and into the trade winds.
Geovoile – Image 8 (click for larger image)
The ball slows…
The ball had almost stopped bouncing; Team AkzoNobel and Team Sun Hung Kai / Scallywag were now the most southerly boats in a north-easterly trade wind with their bows pointing roughly at the finish line. However, the leverage was still there with 155nm between Team Sun Hung Kai / Scallywag in the west, and Turn the Tide on Plastic in the east, so we’re not quite done with this play yet.
Headed for the Doldrums
If we now bring it up to date with Image 9 from 13:00UTC today, 13th February we can see that the leverage has eased down, it’s now about 90 miles from the east to west wings of the fleet. While the two western boats currently hold a 50nm mile lead over the rest of the fleet.
Geovoile – Image 9 (click for larger image)
It’s likely that the rest of the leverage will slowly disappear as the fleet sail south in the trade winds for the next couple of days. The probability is that they will all target roughly the same spot to hit the Doldrums, and converge as they head for it. So let’s have a look at the Doldrums right now – finally, a climate zone transition!
The east pays back
In Image 10, we have added the Predicted Route for the fleet, running out from their positions at 13:00UTC today. We can see the fleet converging on a point in the Doldrums to the east of their current position. If they do all go for this point then it will allow the eastern boats to make up some of their lost ground, as they will be sailing a more open, wider wind angle to get there, and – everything else being equal – they will be faster through the water.
Geovoile – Image 10 (click for larger image)
Let’s take a look at the bigger picture in Image 11 to see what they face between here and Auckland. The boats have moved a couple of days down their predicted route, to 19:30UTC on the 15th February – about the time we can expect them to hit the Doldrums. And after a couple of days of pleasant and relatively low stress sailing, it’s going to get messy for the weekend.
Geovoile – Image 11 (click for larger image)
The first point from this image is that the Doldrums are almost non-existent and they are clearly much narrower to the east – so that should indeed allow the eastern boats to make up a fair bit of lost ground as everyone races to get to the east. I don’t expect the lead to change hands though.
Meet Gita, the cyclone…
The second point is that from here on, nothing will be normal (like it was so far, right?). The reason is the purple patch of 50+ knot winds to the north of New Zealand – welcome to the party Cyclone Gita. Gita is going to have a massive impact on the routing from here on in, as you can see from the predicted routes skirting far to the west of the northern tip of New Zealand, before they head back east to get to the finish line.
The track of Gita is unpredictable, but the broad consensus is that it will move west towards the coast of Australia before dipping south. It will get about as far south as the middle of the North Island, and then move eastwards to cross New Zealand – looks like Auckland’s power infrastructure could take another hammering.
Sucking out all the energy
The problem for the fleet is not that they are at any risk from this cyclone, but that it will take all the energy out of the atmosphere with it when it moves south. If we have a look at Image 12 from 02:00UTC on the 20th February we can see Gita centred just south of Auckland. To the north of it there is a massive area of light winds that has been left behind in the wake of the cyclone.
Geovoile – Image 12 (click for larger image)
The south-east trade winds are almost non-existent, and when the breeze is restored after Gita departs it’s going to be blowing from the south-southeast. So the fleet will be unable to sail a course to the top of New Zealand – hence the massive detour in the predicted route. They could end up sailing upwind through the Tasman Sea.
A testing time
Now, this forecast is six days ahead and there is still disagreement between the different models on the precise path that Gita will eventually take. So we might end up seeing something completely different actually happen… The only thing I’m sure about beyond the weekend is that this leg is going to continue to test the navigators and skippers.
Fortunately, things are more predictable in the short-term. The next couple of days of trade wind sailing will be a straight-forward drag race, and I think there will be a consensus that east will be best when they hit the Doldrums. The Doldrums crossing ought to be a lot easier than it was going the other way on Leg 4, and they should clear relatively easily by the morning of the 17th February – as depicted in Image 13 from 01:00UTC on that date.
Geovoile – Image 13 (click for larger image)
After that they should be getting a westerly from the very northern edge of Cyclone Gita, and from this moment onwards their wind will be heavily influenced by the movement of the cyclone. If it plays out as predicted, they will have a day or so of westerly before the chasm depicted in Image 12 opens up around them and things start to get really interesting again… I’ll be back after the weekend to see how it unfolds.
via The Volvo Ocean Race Official News http://ift.tt/2wY4Er9
February 14, 2018 at 04:51AM