At noon today, 17 solo sailors leave Opua for Southport on the Gold Coast of Australia. PredictWind meteorologist Arnaud Monges delivered the overnight weather briefing, and here is what the models are showing.
Act one: the front
A low pressure system, L1, sits at 997 hectopascals in the middle of the Tasman Sea with a cold front trailing east. This system drives the first half of the race.
At the start, Opua is forecast to have 15-20 knots from the northeast and one-metre building seas, pushed along by a high pressure system moving clear of New Zealand. By Sunday midnight, as the fleet rounds Cape Reinga, wind is up to 25 knots from the northeast, seas 2.5-3 metres. At Monday noon, in the open Tasman, boats hit the front: north winds 25-30 knots, gusts 35-40 and potentially higher in rain squalls, seas 3-4 metres. The fleet will be reaching at that point, taking wind and waves from the starboard side. The routing model flags a strong roll signal throughout day two. “It can be unsafe. It will be difficult to walk around the boat.”
One complication: the cold front is moving slowly, pinned by a strong blocking high to the east. The fleet will be inside it longer than a fast-moving front would produce.
Between the systems
After the front clears, winds drop to 10-15 knots and back west to southwest for roughly a day to a day and a half. Boats that have pushed hard through the front have some room to recover before the next system arrives.
Act two: L3
By Wednesday, a second low pressure system, L3, is forecast over Tasmania, bringing another cold front and winds of 25-28 knots with seas to 3.5 metres. Boats will be going upwind, which trades the violent rolling of the reaching legs for vertical acceleration and bow slamming as the bow punches through waves rather than riding over them. The routing model shows a stronger slamming signal here than during L1.
Thursday should bring lighter westerly conditions as the fleet closes on the Queensland coast.
The numbers
All four models agree on a seven-day crossing. True wind speed averages 15-20 knots across the passage, with gusts reaching 40-plus during L1. Average boat speed modelled at 7.5 knots using a Beneteau First 36 polar. Sailing mode: 70% reaching, 30% upwind, no downwind.
A Saturday start was compared against Sunday, Monday and Tuesday departures. Leaving Sunday or Monday produces stronger conditions than today, not lighter. Tuesday would be the first genuinely easier window. The Race Committee has already made the call confirming the Saturday start, and given this weather update does not significantly change the outcome, there is every reason to expect a race start at 12:06 today for the monohull fleet (12:00 for the two multihull’s in the race).
Follow the fleet
The tracker is live from noon today at boatingnz.co.nz/sttc.
