How to read a surf forecast to get the best surfing experience

Think of this post as your Bachelor in Understanding The Surf Forecast degree — for example, at the University of California, Los Angeles (UCLA). You will learn the basics of reading surf forecast in a right way to have the best surfing experience.

What is surf forecast?

The surf forecast is the same weather forecast as for any other sports or outdoor activity. What sets it apart from the snow forecast is, understandably, its own set of weather parameters. In the case of surfing, these are the three most important things to know and understand: swell, wind direction and wind gusts, and tides. Let's deal with everything in order:

Swell

Waves are always the result of mechanical action — for example, the impact of the wind or a boat.

If we don’t feel the wind but see the waves, it doesn’t mean that they are formed on their own, but most likely are the result of the storm, raging somewhere far from here. If you put your finger into the water, you will create circles, waves. This happens because we acted on the water mechanically. Wind affects water in the same way — mechanically.

Waves are formed because of the blowing wind, and then they roll over the entire surface. That is why we can see waves in a completely calm places. The set of unrest on the surface of the water formed by the “far away” wind is called a swell.

So swell is a collection of waves generated by specific conditions like a storm. Swell can travel a long way to the beach (think like 2000 miles offshore). The swell height, period, direction are the ones that determine how surfable is the swell.

For your Surfing Degree, these four variables are the basics: swell, swell size (or swell height), swell period and swell direction. Understand this holy foursome and you will have a decent package of know-how and you are ready to start planning your next surf session.

Swell size (Swell height). The swell height is measured from the base of the wave to the top of the wave. Note: swell height does not always mean the height of the wave as it is an estimated average height of the highest one-third of the swells. Generally, this parameter gives you a picture of the average height of the possible waves.
Swell period. An extremely crucial part of surf forecast — also known as a swell frequency. Measured often from one peak to another peak. Correlates in how much energy there is in a swell. A thumb rule: the longer the period the more energy in waves.
Swell direction. The direction from which the swell is coming. A thumb rule: the more directed the swell is when hitting your local beach the stronger the waves. Look for islands that might block the incoming swell.
Swell energy. Indicates the power of the predicted waves and can be the most useful guide to how powerful the surf is likely to be. It is a combination of both wave size and period.

How to read a surf forecast. Valerya Milovanova / Windy.app

Wind direction and wind gusts

The quality of the waves depends on the wind direction on the coast. If the wind blows from the shore towards the water — this is an offshore. Such a wind maintains waves from collapse and makes them sharper.

The wind blowing towards the shore is an onshore. Onshore blows off the peaks and causes the waves closure ahead of time. It is the most unwelcomed wind for surfers.
The wind blowing along the shore is a cross-shore. In this case, everything depends on the force and direction of the wind. Such a wind can either slightly spoil the waves or ruin your vacation.

Wind gusts is a sudden increase in the wind’s speed that lasts no more than 20 seconds. With strong wind gust, it can change the surfing conditions rapidly. A good thump rule: 9 mph gusting to 18mph will make surfing conditions messy.

Tides

There are two main types of tides:

At low tide the water level drops to its lowest and flows from the coast.
During high tide the water flows to the coast.

The low and high tides are really depends on the spot and you should always ask the locals about the best timing to get out in the water. Most often it’s when the tide is moving either “low going high” or the tide is on the rise. Usually, at low tide reefs and stones are exposed.

Learn more about reading the tide tables.

How to read surf forecast in Windy.app?

The surf forecast is avaliable in two places in the app: on the Sweel Map in the Weather Map and in the Spot Screen.

Swell Map in the Weather Map

1. Take a look at the colors on the map. It indicates the swell size or the height of the waves: from 0 (blue) — no waves, to 3.2 meters (magenta) — very big waves.

2. Zoom the map to the region you want to get a forecast for. It could be your favorite spot or the closest one to your current location.

The white triangles on the map shows the waves and its direction, which is FROM where the waves are coming. For example, for the popular Carmel Beach surf spot in Monterey, California, USA, the direction of the swell is west-southwest (WSW) on the screen right next. So reading swell direction is the same as reading wind direction.

Swell Map in the Windy.app for iOS

3. Click on any point on the map to get an accurate swell forecast if you don’t need or don’t know the exact spot. It shows you the coordinates of the spot also in degrees: N 27.2612, W 115.62.

Swell Map in the Windy.app for iOS

4. If you still need to find a spot for surfing, open the Weather Map's Extra Setting to find the surf spots closest to you faster by hiding all other types of spots.

Swell Map Extra Settings in the Windy.app for iOS

Spot screen

5. Go to the spot screen clicking on it to get the most detailed forecast, including swell's other basic parameters, besides the direction. As a general rule:

Swell size (or swell heigh). 1 meter, m (3.5 feet, ft) to 3 m (10 ft) is a good size of waves for an amateur surfer.
Swell period. 8 seconds (s) — normal surfing, 11 s — good, 14+ s — great (pure groundswell).
Swell energy. 100 kiloJoule (kJ) — surfable waves at many breaks, 200–1000 kJ — punchy waves, 1000–5000+ kJ — heavy and dangerous waves at some breaks.

Swell forecast (wave forecast) in the Windy.app for iOS

Additional advice:

The modern weather forecast is scientifically as accurate as possible but as anyone who has been in the water and witnessed the ever-changing nature of Mother Nature (sometimes you can go in an hour from great surf into abysmal) – make sure you have this covered:

See if there are live stream cameras available at the spot, check the current forecast and see how it looks like in reality.
Ask the locals in the Windy.app local chats how are the surfing conditions.
In the end, with surf forecast the same thing applies as with surfing itself – the more time you spend at your local surf spot, the better you become.

Where to find surf forecast in Windy.app?

Windy.app provides surf forecasts for surf spots all over the world. To see it, open any spot in our app and tap on Surf Weather Profile next to the.

Open the Weather Map from the Home screen of the app. Then select "Swell" in the weather parameters slide under the wind icon. At the same time, the map's weather model will change to MFWAM.

Home Screen of the Windy.app for iOS

This post was originally published in the Windy.app blog on February 26, 2019.

Learn more about how to read the surf / swell forecast in a special Windy.app presentation with examples and tips from professional surfers with many years of experience of riding the biggest and best waves on the planet.

Text: Windy.app team and Ivan Kuznetsov, an outdoor journalist, editor and writer from the Dolomites, Italy, and Karelia, Finland, with 10 years of professional experience. His favorite sports are hiking, cycling and sauna. Read his other articles

Cover photo: Austin Neill / Unsplash