Cape of Good Hope, Southern Ocean, South Indian Convergence Zone, Ice Restriction Zone - Alan Roberts explains
The Cape of Good Hope is a significant point on the race course and sits just before Cape Agulhas – the most Southern tip of Africa and the official meeting point of the Atlantic and Indian Oceans. For our sailors its ticks off the first of the three capes to be rounded (Cape of Good Hope) and means that the Southern Ocean is next. South of the Cape of Good Hope the depths change with underwater sea mounts and plateaus that cause upwellings and funky current effects in the sea, that can kick up some disturbed wave pattens and affect the winds.
The systems all move from West to East with low pressures that fire across the Southern ocean. The aim for all the skippers is to find a system, and sail fast ahead of it. Choosing their position along a front the skippers will have to compromise and balance between; the shortest distance to sail, the amount of wind they will see & the sea state. These boats don’t necessarily go faster the more wind they have, the sweet spot is about 25 knots of wind, anymore and the sea picks up and they will have to slow down. Of course, each boat is different and will adapt their strategy according to their strengths or weaknesses. Also, each skipper will analysis the situation in their own way.
The shortest distance around Antarctica would be to sail as far South as possible. They are however limited with an ice exclusion zone, the idea of this zone is to keep the boats out of the way of icebergs to reduce the risk to the boats of colliding with them and therefor to limit any rescue scenarios in extreme Antarctic environments.
The South Indian Convergence Zone (SICZ) is a band that sits off the eastern part of the African continent, it is quite active at this time of year and although the boats will not be near the band, it influences a lot of the weather in the Southern Ocean.
The boats will take around on month to sail 11,000 miles between Cape of Good Hope and Cape Horn, it’s a large section of the race course. Not just because of its distance, weather and remoteness but also mentally. Until now there have been many points along the race course, Spain, the Canary Islands, Cape Verde, Brasil and South Africa where you could potentially stop if you had to. This large vast ocean can be overwhelming if you think about crossing it in one hit, the key for the skippers will be to break up this segment, take it on step by step and keeping a positive mental mind frame while pacing themselves and looking after the boat.
Currently we see the boats with very different trajectories and speeds. The conditions are very unstable with clouds that can produce wind out the front and big wind holes under or behind them, like in the doldrums, except this time the clouds are moving in the same direction as the boats meaning the can stay in them for a long time with no or little wind. Is it worth changing sail just for a couple of hours? Probably not... it’s a lot of energy and risk, but each skipper will have their own opinion and tactics.
This is Clarisse’s second Southern Ocean, second Vendee Globe, it means she’s more experienced, but it may also means she is more aware of what it will be like and anxious about the large gains or losses that can be made. She’s just hanging on to a good group of boats with Justine, Sam & Boris. As they ride the current low pressure the next system is lining them up, they will have to avoid a high pressure with light winds in the middle that will be crossing ahead of them moving from South West to North East. Then they will be looking to pick up on a small low pressure that shoots down behind the high, this new low pressure if forming off the SICZ and spinning off fast towards the South West.
They are in for the long run now, boat preservation, sensible decision making and a risk v reward balance will be essential to making it around the Antarctic for everyone!