Predictwind’s metrologist Arnaud Monges expects the Rolex Fastnet Race to get underway in a 12-14kts WSW breeze, with a building current from an easterly direction.

The boats will sail upwind pushed by the current in the opening stanzas of the race. The wind against current condition is not expected to have an impact on the sea-state with waves topping out at 1-1.5metres at 8sec period.

Skippers Briefing and Predictwind weather update – RORC – Cowes – July 25, 2025 – photo © Arthur Daniel / RORC

The 450 competitors in the total fleet were told to expect a steady weather pattern over the next five days.

“The big players are the low pressure over Iceland, which is very deep, and we have the High over the Azores, which is going to control the next five days – for the entire race.

The two weather systems create a westerly wind in the open ocean, in the Atlantic. As the westerly approaches Ireland it splits into two directions, one of which a north westerly which will be active while the fleet cross the Irish sea, and have to sail hard on the wind, and will not be able to stay on the direct route for Fastnet Rock off the southern coast of Ireland.

“The high and the ridge are not very strong this weekend. So the weather, especially on Sunday, is going to be on the lighter side.”

Géry Trentesaux at the helm of Long Courrier – Rolex Fastnet Race – photo © Paul Wyeth / PW Pictures

“But next week, especially on Tuesday, the high is going to be very powerful, and it’s going to control the system, and there are going to be very steady conditions.”

Line honours contender SHK Scallywag – Rolex Fastnet Race – photo © Carlo Borlenghi

The race will start in a westerly breeze, but as they move into the Irish Sea it will swing northwest.

“In the Atlantic, a secondary low developing. It’s a small player. It’s not a deep low, but it’s actually going to influence the weather on Sunday,” explained Monges.

“At noon on Sunday, we still have the high and we’ll still have the North West gradient, but the low, is approaching us and it’s making the wind flicker. On Monday, the high is still there, as is Northwest gradient. On Tuesday, it’s even stronger, it changes a little bit to the left, but it’s still the same weather pattern and same again on Wednesday.”

Oystercatcher XXXV at the start of the breezy 2023 race – Rolex Fastnet Race – photo © Rolex / Kurt Arrigo

Monges says the playbook for the race is that the high pressure is going to control the race. “It’s going to make moderate, consistent and fair weather conditions and on Sunday, maybe it’s a lighter day.”

He says the preferred weather feeds are UKMO and Arome at 2km resolution.

By way of an example he used the popular Sunfast 3200 for his weather routing exercise. That showed all six feeds being in agreement until the boat reached Lands End at the SW corner of the English coast. The routes showed a straight run down the coast, but when the boat reached ther Irish Sea the routes diverged.

For both the synoptic weather situation and the routing he emphasised that the models are updated frequently, and that competitors would need to keep checking regularly.

Using the Sunfast 3600 as an example, Monges expected it to take 4-5days for the route from Cowes to Cherbourg, rounding Fastnet Rock and the Scilly Isles to port, and staying clear of restricted areas. The average wind speed is expected to be 12kts, and 90% of the time the breeze should be between 8-20kts. The strongest breeze is expected to be 18kts with gusts to 20kts.

“This high pressure system will make fair weather conditions,” he said.

Using the same Predictwind Routing function, and some adjusted Polar charts – to read off boat performance on a given wind angle, and 12hrs before the race start, Sail-World got an expected sailing time of 1 day 10hrs for the Ultim foiling trimarans; 3 days 9hrs for the TP52s (50fters) and 3days 14hrs for the 40fters. The sample 50fter was expected to finish on Tuesday evening around 2130hrs.

by Richard Gladwell