Retrospective · ARC 2025 · cruising rallyHow far south before turning west?
On the morning of the ARC 2025 start, none of 51 forecasts had their best route crossing 25°W south of 24°N. 62% of the cruising fleet went south of it anyway. A year earlier the forecasts split. In both years, no forecast’s best route went to the deep south.
Published Covers 2025, with 2024 for comparison
- The decision
- How far south to go before turning west. It’s made in the first three or four days off Gran Canaria, and it’s hard to undo.
- What the forecast said
- In 2025, north of 24°N in all 51 forecasts. In 2024 the forecasts split three ways, with 17 north, 10 on the rhumb line and 24 on the classic southern route. In both years, the deep south was the best route in none.
- What it cost
- The deep south typically cost a 46-footer 1.3 days (2025) and about a day (2024) in the forecast, and about a day (2025) and 1.5 days (2024) when we sailed the fleet’s typical deep-south track through the weather that actually happened. What it bought was a gentler sea.
The decision
Every ARC skipper faces the same question off Gran Canaria. The rally handbook puts it plainly. Sail south until you are sure you’re in the trades before turning west, and use a weather router or forecast to help decide.
We name each option by where the route crosses 25°W, roughly 500 miles out. The four routes on the map are the ones the 2025 cruisers actually sailed, using the typical track of the boats in each band. They’re nearly the same length, apart from the deep south (130 NM further), so any difference in time comes from where the wind is.
What the forecast said on start morning
We took the ECMWF ensemble forecast issued at 00:00 UTC on each start day, which gives 51 equally likely versions of the next 15 days. For each one we found the fastest route for a typical ARC cruiser, an Oceanis 46.1 sailed at 78% of its ORC polar (comparable cruisers sailed at about that in 2025). Ocean currents are included.
2025 was unusually clear. Every forecast’s best route crossed 25°W north of 24°N, with a median near 27½°N. 2024 wasn’t. The forecasts split 17 north, 10 on the rhumb line and 24 on the classic southern route, and the option that held up best across all of them was the classic southern route, crossing 25°W near 23½°N.
What neither forecast could settle was the second half. By 40°W the forecasts’ best routes spread from 21.9°N to 25.9°N in 2025 and 20.8°N to 27.3°N in 2024 (8 forecasts in 10). That decision belonged to a fresh forecast a week into the passage.
How far south? The forecast on start morning against the fleet
- Best route in each forecast
- Where the cruisers crossed
Show the numbers
| Crossed 25°W at | Forecasts | Cruisers |
|---|---|---|
| 29.5–30.5°N | 0% | 2% |
| 28.5–29.5°N | 6% | 4% |
| 27.5–28.5°N | 43% | 7% |
| 26.5–27.5°N | 33% | 5% |
| 25.5–26.5°N | 12% | 7% |
| 24.5–25.5°N | 4% | 6% |
| 23.5–24.5°N | 2% | 16% |
| 22.5–23.5°N | 0% | 19% |
| 21.5–22.5°N | 0% | 18% |
| 20.5–21.5°N | 0% | 11% |
| 19.5–20.5°N | 0% | 6% |
| 18.5–19.5°N | 0% | 1% |
| Crossed 25°W at | Forecasts | Cruisers |
|---|---|---|
| 30.5–31.5°N | 2% | 0% |
| 29.5–30.5°N | 12% | 0% |
| 28.5–29.5°N | 14% | 0% |
| 27.5–28.5°N | 6% | 0% |
| 26.5–27.5°N | 2% | 1% |
| 25.5–26.5°N | 6% | 0% |
| 24.5–25.5°N | 12% | 1% |
| 23.5–24.5°N | 6% | 2% |
| 22.5–23.5°N | 27% | 11% |
| 21.5–22.5°N | 14% | 23% |
| 20.5–21.5°N | 0% | 40% |
| 19.5–20.5°N | 0% | 16% |
| 18.5–19.5°N | 0% | 5% |
| 16.5–17.5°N | 0% | 2% |
What each choice traded off
We then sailed each of the four routes through all 51 forecasts. The tables show the typical crossing, the range covering 8 forecasts in 10, how often each route was the fastest of the four, and what it cost against the best of the four in the same weather.
ARC 2025: the forecast on start morning
| Route at 25°W | Typical crossing | 8 in 10 between | Fastest in | Cost vs the best, typical | …in a bad case (1 in 10) |
|---|---|---|---|---|---|
| North 27°N or more | 19.3 days | 18.7–20.7 | 42 of 51 | – | 5 hours |
| Rhumb line 24–27°N | 19.9 days | 19.3–21.1 | 3 of 51 | 14 hours | about a day |
| Classic south 20.5–24°N | 20.0 days | 19.2–21.4 | 5 of 51 | 17 hours | 1.5 days |
| Deep south below 20.5°N | 20.6 days | 19.7–21.7 | 1 of 51 | about a day | 2.5 days |
Oceanis 46.1 at 78% of polar, 51 forecasts, currents included. “Cost” compares each route with the quickest of the four in the same forecast.
ARC 2024: the forecast on start morning
| Route at 25°W | Typical crossing | 8 in 10 between | Fastest in | Cost vs the best, typical | …in a bad case (1 in 10) |
|---|---|---|---|---|---|
| North 27°N or more | 21.2 days | 20.3–22.2 | 14 of 51 | 12 hours | 1.4 days |
| Rhumb line 24–27°N | 20.9 days | 20.2–22.2 | 3 of 51 | 7 hours | about a day |
| Classic south 20.5–24°N | 20.5 days | 19.8–22.1 | 31 of 51 | – | 17 hours |
| Deep south below 20.5°N | 21.3 days | 20.6–23.0 | 3 of 51 | about a day | 1.5 days |
Oceanis 46.1 at 78% of polar, 51 forecasts, currents included. “Cost” compares each route with the quickest of the four in the same forecast.
ARC 2025: what the crew sails through
| Route at 25°W | Highest sea, typical / 1 in 10 | Hours in seas over 3 m, 1 in 10 | Strongest gusts, 1 in 10 | Hours under 8 knots, 1 in 10 |
|---|---|---|---|---|
| North 27°N or more | 3.1 / 4.2 m | 80 h | 39 kn | 70 h |
| Rhumb line 24–27°N | 3.2 / 4.1 m | 77 h | 38 kn | 88 h |
| Classic south 20.5–24°N | 3.0 / 3.6 m | 56 h | 36 kn | 100 h |
| Deep south below 20.5°N | 2.8 / 3.5 m | 45 h | 33 kn | 91 h |
Within the forecast’s first 14½ days. “1 in 10”: one forecast in ten is this rough or rougher.
So in 2025 the north was most of a day quicker than the classic south, and the deep south slower still. The price of the north was rougher water in a bad forecast, with more hours in seas over 3 metres and stronger gusts. The deep south had the gentlest sea, and no fewer light-air hours than the north. Squalls aren’t in these forecasts, and the handbook notes they become more common as you head west.
On any one route, a good forecast and a bad one were about two days apart. Between the three sensible routes, the typical difference was under a day. Plan water, fresh food and crew flights for the slow end of the range, whichever way you go.
What actually happened
A forecast is only useful if it holds up, so we checked it against the weather that actually happened, using ECMWF analyses through December, with Copernicus currents. To take boat and crew out of it, we sailed every cruiser’s actual track again with the same Oceanis 46.1, and grouped the results by where each track crossed 25°W.
Raw finishing times can’t answer this question. In 2024 the deep-south boats finished first on average, because they were bigger and quicker boats, and some motored.
ARC 2025: every track, the same boat, the real weather
| Crossed 25°W at | Boats | Oceanis 46.1 on those tracks |
|---|---|---|
| south of 20°N | 5 | 20.0 days |
| 20–22°N | 27 | 19.5 days |
| 22–24°N | 44 | 19.2 days |
| 24–26°N | 18 | 19.0 days |
| 26–28°N | 17 | 19.1 days |
| north of 28°N | 11 | 19.4 days |
ARC 2024: every track, the same boat, the real weather
| Crossed 25°W at | Boats | Oceanis 46.1 on those tracks |
|---|---|---|
| south of 20°N | 16 | 22.6 days |
| 20–22°N | 78 | 21.8 days |
| 22–24°N | 26 | 21.3 days |
| 24–26°N | 2 | 21.3 days |
| 26–28°N | 1 | 22.0 days |
In both years the gaps between the three sensible routes closed to hours in the real weather. The forecast pointed the right way, but the real margins were smaller than it suggested. Sailed one by one, the deep-south boats’ own tracks stayed about a day (2025) and 1.3 days (2024) behind the best band.
What to take into ARC 2026
- The question is how far south this year, not “south”. In 2025 the start-morning answer was “hardly at all”, and in 2024 it was “to about 23½°N”. The habit sends most of the fleet the same way every year, with 62% south of 24°N in 2025 and 98% in 2024.
- The deep south was never the best route. Across both years and four boat types, no forecast’s best route went there (0 of 408). It’s a fair choice for comfort, or to stay near the Cape Verde islands, but make it knowingly, because it costs about a day.
- Pick the route that holds up, not the one that wins most often. When the forecasts disagree, choose the option whose bad case is mild. In 2025 that was the north, in 2024 the classic south. The rhumb line was rarely the favourite, but in a bad forecast it was never more than about a day behind the best.
- Decide the first move on start morning, and plan a second decision for day 5 to 7. How far south to go off the Canaries was clear from the start-day forecast in both years. Where to cross 40°W wasn’t. Download a fresh forecast before you get there.
- Plan for the range, not the average. The weather moved the crossing by about two days on any route, and the choice between sensible routes by less than one.
Your boat, and its polar
We repeated all of this for a Hallberg-Rassy 36, a Swan 56 and a 45-foot cruising catamaran. Faster and slower boats arrive days apart, but in each year every boat type ranked the four routes in the same order. You don’t need a precise polar to answer “how far south”, but you do need one for a realistic arrival window.
No polar file? About half of an ARC fleet has none in the public data, including every catamaran. We build a working one from your boat’s type and a few questions about how you sail her, and we tell you how far to trust it.
How we worked it out
- Forecasts: ECMWF IFS ensemble, 51 members, from the 00:00 UTC run on each start day (23 November 2025, 24 November 2024), used at 0.5°. ECMWF open data, CC BY 4.0.
- The ensemble runs to 15 days, but a cruiser takes 18 to 22. Beyond day 14½, every forecast shares the same average trade wind, so the forecast decides the strategy and the shared tail just gets everyone home.
- Waves from the ECMWF ensemble wave model (2025). Currents from the Copernicus Marine global analysis, the currents as they were, which change slowly.
- What actually happened: ECMWF high-resolution analyses, stitched every six hours.
- Boats: ORC certificate polars (via jieter/orc-data), sailed at 78% of polar. The catamaran polar is a ProSail estimate, as ORC doesn’t rate cruising cats.
- Fleet: YB tracker positions for the cruising and multihull divisions. The racing division and boats that stopped in Cape Verde are counted separately. We publish only counts and typical tracks, never individual boats’ tracks.
- Not modelled: squalls, motoring (boats drift slowly in calms rather than motor), sail changes, the Gran Canaria acceleration zones. Two years is a small sample, and we’ll add earlier years.
ProSail compares route options across forecasts to support the skipper’s judgement. It doesn’t promise a safe or a winning route.