You don't need a meteorology degree to read a surf forecast. But understanding the basics — swell, wind, and tides — will transform your surf trip from random luck to informed choices. Here's what matters and how to use it.
Swell: the engine
Swell is what creates waves. It's generated by storms far out in the Atlantic, and travels across the ocean as energy until it hits the coastline and breaks as surf.
Three numbers matter:
Swell height
Usually measured in feet or metres. This tells you roughly how big the wave faces will be. But there's a catch — the height you see on a forecast (like Windguru or Surfline) refers to the open-ocean swell, not the wave face at the beach.
As a rough guide for the Costa Vicentina:
- 1-3ft swell = Small, mellow waves. Great for beginners.
- 4-6ft swell = Solid, fun conditions. Intermediates will thrive.
- 8ft+ swell = Big and powerful. Intermediate-advanced and above.
Swell period
This is the gap in seconds between each wave. It's arguably more important than swell height, because longer periods carry more energy.
- 6-8 seconds = Short-period wind swell. Messy, weak, and close together. Still surfable but less powerful.
- 10-12 seconds = Solid groundswell. Clean, powerful waves with good shape.
- 14+ seconds = Long-period groundswell. Heavy, powerful waves that break with authority. These swells light up spots that don't normally work.
Key takeaway: A 4ft swell at 12 seconds is far more powerful than a 6ft swell at 7 seconds. Period matters more than height.
Swell direction
Where the swell is coming from determines which beaches work and how the waves break.
On the Costa Vicentina:
- W and WNW (the most common) works well at most spots, especially Arrifana
- NW is the dominant winter swell. Exposed beaches like Vale Figueiras and Amoreira light up. Sheltered spots like Arrifana still work but with less power
- SW is less common but can produce punchy waves at south-facing spots
- S is rare but can create surprisingly good conditions at Arrifana specifically
Wind: the quality control
Swell creates the waves; wind determines whether they're good or not. The single most important factor in wave quality is wind direction.
Offshore wind
Wind blowing from land to sea (east on the Costa Vicentina). This grooms the wave faces, holds them up, and creates the clean, peeling conditions every surfer wants. Light offshore is ideal — too strong and it makes paddling difficult.
Onshore wind
Wind blowing from sea to land (west on the Costa Vicentina). This destroys wave quality. The faces become bumpy, choppy, and hard to ride. Onshore is the enemy.
Cross-shore wind
Wind blowing parallel to the beach. Less damaging than direct onshore but still not ideal. Cross-offshore (blowing slightly from the land) is manageable.
The daily pattern on the Costa Vicentina
In summer, there's a predictable pattern: calm or light offshore in the morning, with a sea breeze (onshore) building from late morning and peaking in the afternoon. This is the Nortada — a thermal wind driven by heat differences between land and ocean.
Practical advice: In summer, surf before 9am or after 6pm. In autumn and winter, the pattern is less predictable, but offshore mornings are still the most common and the best.
Tides: the shape-shifter
Tides change the water depth over the sandbanks and reefs, which changes how waves break. The same beach can look completely different at low tide versus high tide.
How tides work
The tide rises and falls roughly twice a day on a cycle of about 12.5 hours. High tide and low tide are each roughly 6 hours apart. The range varies — during spring tides (around full and new moons), the difference between high and low is largest. During neap tides (quarter moons), the range is smallest.
What this means for surfing
Low tide: Waves break in shallower water, so they tend to be more powerful, hollower, and faster. Sandbanks and rocks may be exposed. Good for experienced surfers who want more intensity.
Mid tide: Generally the most consistent conditions. The waves break with good shape but less extreme power. Most beaches on the Costa Vicentina work best at mid tide, especially on an incoming tide (rising).
High tide: Waves break closer to shore in deeper water. They tend to be fatter, shorter, and sometimes "dumpy" (breaking all at once rather than peeling). Some spots stop working at full high tide.
Our tip: Start your session 2 hours before high tide on a rising (incoming) tide. The waves improve as the water comes in, and you'll get the best shape at the end of your session.
Putting it all together
Here's a real example. Say the forecast for tomorrow shows:
- Swell: 5ft at 11 seconds from the WNW
- Wind: E 8km/h in the morning, W 20km/h in the afternoon
- Tide: Low at 7am, high at 1pm
What this tells you: Solid, clean groundswell from the right direction. Offshore wind in the morning that will turn onshore by lunchtime. The tide will be rising all morning.
What you'd do: Get to the beach by 8am (tide rising from low, wind still offshore). Surf until 11am or midday when the wind starts to turn. Arrifana would be a great choice — the WNW swell wraps in nicely, and the rising tide through mid-tide is when it works best.
Where to check forecasts
- Windguru — our go-to for wind and swell data. Free, accurate, and shows multiple models.
- Surfline — good for surf-specific forecasts with spot descriptions.
- MSW (Magic Seaweed) — user-friendly with star ratings for conditions.
Or just ask us. When we deliver your gear, we'll share what we know about the current conditions and which beaches are working. It's part of the service.
Want the right board for the conditions? We match your gear to your level and the current swell. Get in touch to book.