How to read the Spanish marine forecast, line by line

Which forecasts there are and when they come out

The official source in Spain is AEMET’s marine forecast, which has two main products:

• Coastal: waters up to 20 miles offshore, by area. This is the one you want for a day trip. It gives the forecast for 24 hours and a trend for the following 24. It is updated at 12:00 and 20:00 official mainland time.
• High seas: large areas of the Atlantic and the Mediterranean, for passages. It is updated at 08:00 and 20:00 UTC.

The same content reaches you on board via NAVTEX and VHF: Spanish Maritime Rescue announces the forecast on channel 16 and broadcasts it on a working channel. In Catalonia, Meteocat also publishes its own coastal forecast.

The three parts of a forecast

Take the example at the top. Although each service has its own format, the order is almost always the same:

1. Warning. It comes first because it matters most. If there is a warning for your area, the rest of the forecast is secondary.
2. General situation. Where the lows and highs are and where they are moving. In the example, a low south of the Balearics and a high over France: between them, an easterly or north-easterly wind over Catalonia. If you know how the wind turns around lows, this line already tells you almost everything.
3. Forecast by area. Wind, wind sea, swell and weather, in that order.

Wind: direction, force and changes

Northeast 4 to 5, increasing 6, occasionally 7 in the north in the afternoon.

• Northeast: where the wind comes from, not where it is going.
• 4 to 5: force on the Beaufort scale. Force 4 is 11-16 knots; force 5, 17-21. It is the mean wind: gusts will be stronger.
• Arreciando (increasing): getting stronger. Amainando (decreasing): easing. Rolando (veering/backing): changing direction («rolando a norte»). Variable: light and with no fixed direction.
• Occasionally, temporarily: not all the time or over the whole area, but it may happen. Plan for the higher value.
• In the north, in the afternoon: the forecast covers a large area. Always read where and when.

The sea: wind sea, swell and combined sea

Marejada to fuerte marejada. Swell from the east, 1 to 2 metres.

• Wind sea: raised by the wind blowing in the area. It is given with the names of the Douglas scale: marejadilla (up to 0.5 m), marejada (0.5 to 1.25 m), fuerte marejada (1.25 to 2.5 m), gruesa (2.5 to 4 m)…
• Swell: waves coming from elsewhere, from a distant or past storm. It is given with direction and metres. The waves are long and regular, and they steepen near the coast and at harbour entrances.
• Combined sea: the sum of the two. It is what really moves the boat, and what AEMET uses to decide on warnings.

Heights are significant wave height: according to AEMET, the mean of the highest third of the waves. Some individual waves will be considerably bigger. And when the swell comes from a different direction to the wind, as in the example, you get an uncomfortable cross sea even if the figures do not look big.

Weather and visibility

Showers. Visibility good, moderate in showers.

The forecast ends with the phenomena (showers, thunderstorms, fog) and the visibility: good, moderate or poor. For a coastal trip, what matters most are thunderstorms, because of the gusts coming out of the clouds, and fog, which in spring can form over the cold sea even when it is sunny on land.

Warnings

WARNING: force 7 in the north of the area from the afternoon.

AEMET issues a coastal waters warning when it expects within the next 24 hours (official criteria):

• wind of force 7 or more;
• a total sea of 3 metres or more in the Mediterranean (4 in the Atlantic);
• thunderstorms or very heavy rain;
• visibility under one mile.

Check the warnings in force on AEMET’s warnings map.

From forecast to decision

With the forecast read, three questions:

1. Is there a warning for my area? If there is, you don’t go out.
2. What is the worst moment of the day and at what time? If the wind increases in the afternoon, go out in the morning and come back early.
3. Does what the forecast says match what I see? The barometer, the sky and the buoys of Puertos del Estado tell you whether the forecast is coming true.

To fine-tune when the wind will veer or increase, compare models on Windy (I explain it in weather models and Windy). And to get to know the winds on our coast, see the guide to the winds of the Catalan Mediterranean.

Frequently asked questions