Leg 5 of the Volvo Ocean Race could be set to produce record breaking high speed sailing as the six boat fleet takes on fierce storms and huge ocean swells on their way from New Zealand to Brazil.
Onboard Abu Dhabi Ocean Racing - Volvo Ocean Race
With no more than a week to regroup after finishing the punishing fourth leg from China the teams have had to hustle in Auckland to be ready for what is likely to be their toughest test yet - a daunting Southern Ocean passage around Cape Horn to the Brazilian city of Itajaí.
At 6,705 nautical miles (nm) Leg 5 is the longest of the race and takes the boats into the world’s most remote and inhospitable stretches of open ocean.
On their way to Itajaí the crews will face ocean swells the size of buildings, storm force winds, freezing temperatures as well as taking on Chile’s infamous Cape Horn.
Bordered only in the south by the frozen wastes of Antarctica, the Southern Ocean is characterised by rapidly moving low pressure storm systems that circle the world’s lower latitudes unfettered by major landmasses to slow them down.
Fed by the steep temperature gradient between the Antarctic Ocean and the South Pacific these high intensity weather systems can generate winds up to 60 knots as they tear eastwards.
According to race meteorologist Gonzalo Infante Leg 5’s predominantly broad reaching- downwind sailing conditions could well see a new IWC Schaffhausen Speed Challenge 24 hour distance record set.
'This is going to be a leg for fast downwind sailing,' Infante said. 'Based on data from previous races and current weather models we expect the boats to sailing fast open angles in average winds well over 20 knots. This is the sweet spot for Volvo Open 70s and we could see some huge 24 hour runs.'
However Infante says the highly volatile nature of the Southern Ocean weather will require the teams adopt aggressive navigational strategies on Leg 5.
'The main influence on the weather in this region is the South Pacific sub tropical high pressure system which typically generates strong westerly winds on its southern extremities,' Infante explained.
'When this is the case the strategy on leaving New Zealand is to immediately dig hard to the south to get into the westerly ‘storm track’ as soon as possible for a fast run towards Cape Horn.
'But keeping up with an easterly moving weather system travelling at up to 25 knots is not simple.' Infante said. 'It is easy to be overtaken by the front and fall into the lighter winds closer to the centre of the system. Staying in the best winds requires perfect timing and some aggressive course changes to keep up with the lows. Unfortunately, this will be restricted by the ice limits.'
On board Puma Ocean Racing - Volvo Ocean Race
Infante says the already dynamic weather scenario can be further complicated by other low pressure system cyclogenesis areas which influence how and when the storms behave.
'Most of the Low pressure systems are born east off New Zealand, in Mid Pacific, Tasman Sea to the west of New Zealand, or drift down from the north in the form of decaying tropical depressions and cyclones,' he said.
'If a tropical lows get in phase with existing systems they can re-intensify as they feed off the Pacific to Southern Ocean temperature gradient. Most of the time this can cause a split the South Pacific sub tropical high pressure, making the overall situation more complex.
To avoid the fleet running the risk of encountering ice flows off Antarctica race organisers have imposed an ice exclusion zone to keep the boats north of the highest risk area.
'As ever, safety is paramount,' Infante said. 'We will be monitoring the ice flows carefully using daily satellite imagery. The exclusion zone will keep the fleet away from a danger area known as the South Pacific cone of ice.'
After negotiating the extremes of the Southern Ocean the fleet has to round the rocky outcrop of Cape Horn at the southernmost tip of Chile before turning north and passing the Falkland Islands on the way to the finish in Itajaí.
'The Horn approach will depend on the strategy chosen in the Pacific. In this are the interaction between the strong westerlies and the barrier of the Andes is potentially very dangerous, as many sailors can report'
'The section from Cape Horn to the finish could still be a fast reach,' said Infante. 'But the approach to Itajaí is normally tricky with a more dynamic and variable weather'.
'It could provide a strategy nightmare before they finish Leg 5,' Infante concluded.
The start of Leg 5 will be at 1400 local time in Auckland on Sunday March 18 (0100 UTC March 17).
Volvo Ocean Race website