How to read a surf forecast (and never miss a session)
Three numbers, two ideas and the classic Mediterranean traps: everything we look at before choosing the spot of the day, explained with no fluff.
Reading a surf forecast isn’t magic: it’s three numbers and two ideas. The thing is that nearly every guide out there is written with the Atlantic in mind, and the Mediterranean plays in another league, with rules of its own. This is the guide we would have liked to have when we started.
The three figures that matter
1. The height (Hs)
Forecasts don’t give you "the size of the wave you’ll see", they give you the significant wave height (Hs): the average of the biggest third of the waves. In practice: the good sets run to 1.5-2 times the Hs. A forecast of 0.5 m with a decent period means waves of up to a metre when the set comes in. That’s why a Mediterranean "0.4" goes a lot further than it looks.
2. The period (Tp and Tz)
The period is the time between waves, and it is the most underrated number in the forecast. The longer the period, the more energy every wave carries, the more organised the sea arrives and the more face you get. Tp (peak period) belongs to the dominant family of waves; Tz (mean period) mixes the whole sea together. In the Mediterranean: below 4 s it’s pure wind soup; 5-6 s is already surfable; 7-8 s is a good day; 9+ s, a proper storm. Fine detail: if Tz gets close to Tp, the sea is coming in clean and organised.
3. The direction (in degrees)
Swell direction is given in degrees (where it comes from): 0° north, 90° east, 180° south, 270° west. On our coast the two families in charge are the llevant (E-NE, ~60-100°), which lights up the city of Barcelona and the Maresme, and the garbí / southerly seas (S-SW, ~180-230°), which wakes up Castelldefels, Sitges and Vilanova. Every beach has its own orientation, and that is why the spot of the day depends on the storm.
Wind sea and swell: the idea that changes everything
All waves are born from wind, but not all waves are the same. Wind sea is waves just generated by the wind blowing here right now: peaky, messy, with no defined face. Swell is waves born far away (in a storm between the Balearics and the Gulf of Lion, for example) that have travelled long enough to organise themselves into clean sets with a shoulder and a face.
The Puertos del Estado table separates them into different rows, and that is 80 % of the read: if the swell dominates the wind sea, the day looks promising. If it’s all wind sea, you’ll paddle a lot for very little face. In the Mediterranean, with such a small sea, there is almost always a mix; the art is catching the window in which the swell wins.
The fourth factor: the local wind
You can have perfect waves in the forecast and a horrible day in the water because of the wind at that moment. Offshore (from the land out to sea; in Barcelona, the NW terral) smooths the surface, holds the wave open and makes it cleaner. Onshore (from the sea towards land) crumbles it. The local classic: the day after a llevantada (an easterly blow) with the morning terral = glory. Careful with the wind arrows in the table: they show where the wind is going, not where it comes from.
The GMT trap
The official table runs on GMT time. In Barcelona: add 2 hours in summer and 1 in winter. If the peak of the storm says "14:00", in August that means 16:00 on your watch. More than one session has been lost to this detail.
Our method in 5 steps
- Total sea: is Hs ≥ 0.4 m with Tp ≥ 5-6 s in the next 48-72 h? If not, plan B (SUP, surfskate, training).
- Swell vs wind sea: is the swell dominating, or will it once the wind drops? That’s the moment to mark in red.
- Direction: where is it coming from? Llevant → Barcelona and the Maresme. Garbí/southerly → Castelldefels, Sitges, Vilanova.
- Local wind hour by hour: look for the window with offshore wind or no wind at all (mornings, when the terral turns).
- Visual confirmation: the spot’s webcam 30-60 minutes before heading out. The camera doesn’t lie: wait until you see a whole set come in.
Where we look (our sources)
The official table for the Barcelona point (Puertos del Estado + AEMET, which we have embedded in The forecast), the animated Mediterranean map to watch the storms being born, the Barcelona buoy in real time to confirm they have arrived, and the webcams for the final verdict. Windguru, Windy or Surf-forecast use similar models: pick whichever you find comfortable, but once you understand the above you’ll read them all.
Pocket mini-glossary
| Hs | Significant wave height: the average of the biggest third of the waves. Sets reach ~1.5-2× Hs. |
| Hmax | The biggest wave you can expect from that sea state. |
| Tp | Peak period: seconds between waves of the dominant family. The turbo. |
| Tz | Mean period of all the waves put together. |
| Fetch | The stretch of open sea the wind blows over while it generates waves: the more fetch, the bigger the swell. |
| Llevant | Easterly wind and sea (E-NE). The one that brings the big days from Barcelona up into the Maresme. |
| Garbí | South-westerly wind. A thermal afternoon breeze in summer; with a low behind it, it pushes a southerly sea onto the whole coast south-west of the city. |
| Terral | Wind off the land (NW): the offshore that grooms the waves the day after a storm. |
Frequently asked questions
What wave period is good in the Mediterranean?
The scale here is different from the Atlantic one: with a peak period of 5-6 seconds it is already surfable, 7-8 seconds is a good day, and above 9 we are talking about a serious storm. The 12-15 seconds of the Atlantic simply don’t exist in this basin, because the sea is small and the fetch is short.
Do I trust the buoy or the model?
The buoy measures what is there now; the model predicts what is coming. To decide whether to go tomorrow, use the model; to know whether the storm has already arrived, look at the Barcelona buoy in real time and confirm it with a webcam.
How far ahead is the wave forecast reliable here?
At 48-72 hours the model gets it pretty right on whether there will be waves or not; the exact size and the fine timing keep dancing until the last day. That’s why we publish surf lessons 3-4 days ahead and confirm the spot almost on the fly.
The theory you learn here. The face, in the water
Come and check the forecast with us: a 1h30 lesson with a qualified instructor at whichever spot works best that day.