How to understand wave prediction?

How to understand wave prediction?

Hello people!

We recently wrote an article with 6 good wave forecasting sites. But do they really work? There is some risk of looking at a website, seeing that the wave forecast is good, getting ready, sleeping early, putting things in the car arriving at the beach and ... it's flat.

an article with 6 good wave forecasting sites

Unfortunately the risk is high, as the quality of the wave is influenced by many things: wave direction, size, direction and strength of the wind and bottom.

wave quality

In Brazil, this last item ends up having a greater impact and it is usually it that ends with the websites' forecasts. We live in a country essentially formed by beach breaks, that is, with peaks with a sandy bottom. Sand moves, right? In other words, you never know if the peak will be right there or if the sand will be scattered.


The best way to prevent a bad forecast is to start understanding how they are made and why the types of waves and wind indicated for your favorite peak are really the best.

I'm not a mega-hyper-specialist, but I tried to study this a while ago, I understood some things that made sense to me and, I think it's cool to share here. But it would be great to hear from experts, so if you're one, don't hesitate to comment below! ????

Remembering that there are no absolute truths in surfing, so you will see a lot of things out there that work very differently from my explanation below. But I would say that it is useful in many cases.

To analyze the surf spots, I usually use the Google Earth app, as you will see below.

Google Earth application

The best ripple for the peak

Generally, the best direction for the ripple of a peak is that which reaches the sand almost laterally from the sandbar. This causes the wave to open and have a longer wall.

This characteristic is very easy to find in the peaks in the corners of the beach, next to rocks or slopes. Let's take Praia do Arpoador and Praia do Diabo, both in Rio de Janeiro, as examples, as it is next to each other and works inversely:

the beach of arpoador and the beach of the devil

Legend has it that the harpooner works best with southeast swell and looks awful with southwest swell. The devil is the opposite. It usually works well in the southwest and looks terrible in the east / southeast. Let's see how a southwest swell enters the two beaches.

Notice that the southwest takes the harpooner from the front, generating the famous breaking waves. Already in the devil, it passes sideways, with the potential to open to the right if the bottom is good. And a southeast swell?

Exactly the opposite happens, take the devil from the front and the harpoon from the side, opening the famous left with a lot of crowd in the south of Rio.

crowd in the zone

The best winds for the peak

Wind is that story ... in excess, it is never good. The ideal is that it is of low to moderate intensity (5 to 10 knots). The best directions are those that form the land, that is, they blow from the land towards the sea. This makes the waves break better and are less disturbed.

form the land

Google Earth also helps you understand the best directions for the peaks you want to analyze. Praia do Diabo, usually works with any light to moderate wind in the west, northwest and north quadrants, which are the ones that are terra terra:

In the harpoon, any wind in the northwest, north, northeast and east quadrants usually works. This would be a little more complicated, but as it has the protection of the stone, it ends up not disturbing.

From the images so far, you must have realized that the harpooner and the devil, despite being side by side, never work together. Yes, my dear, unfortunately you are right. There is one more factor that aggravates this: the fund.

The best fund for the peak

In fact, the fund is the most difficult to predict and is what usually ends up with forecasting apps and websites. In fact, it is impossible to predict with any degree of certainty, but there is something that I have already noticed that can help you.

Normally, when the bottom at the peak is bad, he only has the possibility to get ready when a strong sea wind comes in. In this case, when the harpooner has a bad bottom, I hope a strong southwest wind will enter.

Although it is the worst wind  to surf   there, I know that after it, there are great chances of having a surfing background again. The southwest accumulates sand in the left corner of the beach forming banks.

In the devil, it's the same. And since the bottom there is even more inconsistent, generally good periods of surf are preceded by days of east wind.

If you visit these peaks one day and both are working classics at the same time, run to the mountains, because the world will be ending! ????

Finally, the size of the wave also influences the forecast. Each peak supports a wave size. But keep in mind that Brazil is practically a landlocked country. If you see in the 1-2m forecast, you can trust it. Much more than that, get ready to fight for survival. And less than that, it takes a stand-up paddle to enjoy the look.

In the forecast image, on any website you enter, the direction of the arrows is always where the ripple or wind is going.

Hope this helps! Good waves!

Frequently Asked Questions

What are the key components of wave prediction that surfers should understand, and how can this knowledge enhance their surfing experience?
Key components include swell size, direction, wind conditions, and tide. Understanding these factors helps surfers choose the best times and locations for surfing, leading to a safer and more enjoyable experience.

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