How To Read a Surf Report - Surfing Theory - The Wave Shack (2024)

🕓 12 min read

✏️ Updated on 26th March 2024

Intro

Hola surfing amigo’s, in today’s blog post I’ll be explaining ‘How To Read a Surf Report’. We’ll go through everything that’s packed into a surf report, so you guys can understand how it all works.

Here are the areas we’re going to cover;

1. The Tidal Chart
2. Surf Report
3. Wave Height – ‘Surf’
4. Swell Rating
5. Primary vs Secondary Swell
6. Swell Period
7. Swell Direction
8. Swell Height
9. Wind
10. Wind Speed
11. Wind Direction
12. Onshore vs Offshore Winds
13. Weather
14. Probability
15. Other Factors to Consider

As I’m based in the UK, I’ll be using the surf reports from magicseaweed.com to explain everything.

It’s a super useful guide, so grab yourself a cuppa and let’s get started!

1. The Tidal Chart

Starting with the easier stuff, the tidal chart (Image 1).

This chart has three easy to understand elements; Tide Times, Chart Datum Measurements and Daylight Times.

Let’s go through each one to find out what they’re all about.

High and Low Tides

So, the four colourful circles shown in image 2 below indicate the high and low tides during a single day. These circles also correspond with the more detailed table on the right, which shows precise timings.

The first yellow circle on the left represents the high tide in the morning, which on this day occurred at 1:46AM. From 1:46AM onwards the tide started to go back out to sea until it reached its lowest point on this day (Blue circle) at 7:59AM. It then made its way back into shore for a second time until 2:27PM (Orange circle) and made its way back out until 8:45PM (Green circle).

You can either use the graph on the left or the table on the right, but both show the exact same information. Fairly simple stuff but hope that all makes sense.

Chart Datum Measurements

The measurements outlined in blue below in image 3 are known as the Chart Datum.

Out of all the elements in a surf report, this is probably the most confusing / least needed… so feel free to skip this section if you want (you have been warned).

Now, a Chart Datum is basically the lowest level to which the tide is expected to fall. There are a few types of Chart Datum but this example uses the Lowest Astrological Tide (LAT) Chart Datum and it’s measured in meters.

Lets go through a quick example using image 3…

At 1:46AM the high tide in the morning (Yellow circle) was 6.7m higher than the Lowest Astrological Tide Chart Datum. Similarly, at 7:59AM the low tide in the morning (Blue circle) was still 3.15m higher than the Lowest Astrological Tide Chart Datum.

I don’t want to get too deep into the factors that effect these measurements but the amount a tide moves changes throughout the year. In the UK for example, there’s a bigger difference between high and low tides in the Winter months than in the Summer months.

Let’s quickly move onto the daylight times before our brains melt.

Daylight Times

This part is easy, it shows the hours of daylight, twilight and night time.

As image 4 shows, the chart on the left has three different shades of grey to indicate the three types of light that occur in one day. Again, there’s a more detailed table on the right displaying the times for; First Light (Yellow dotted line), Sunrise (Blue dotted line), Sunset (Orange dotted line) and Last light (Green dotted line).

Fairly straight forward stuff but all good to know when planning a surfing sesh. And with that we’ve covered all of the aspects that make up the Tidal Chart!

2. The Surf Report

Now, for the more nitty gritty surf report.

The stuff we’ve discussed so far has been about what the tide is doing and when its happening. The remaining sections will go through all the elements of the main surf forecast table so we can fully understand how to read a surf report.

We’ll go through the table columns (Image 5) from left to right.

3. Wave Height – ‘Surf’

Although this column is called ‘Surf’ it’s actually talking about wave height. Believe it or not, methods for measuring wave height differ depending on where you are in the world.

As surf forecasters, magicseaweed.com use the standard measurement method – measuring the wave height from the peak to the trough as shown in image 6.

These measurements are usually shown in feet but meters is equally fine like in the table in image 5 (above). Notice that the surf report will always give a wave height range. This is because every so often a swell will chuck out a wave larger than the others.

Going back to the different measurement methods, surfers in Hawaii measure waves very differently. The height of a wave in Hawaii is from the peak to the back of the wave. As image 7 shows below, that can make a big difference in apparent wave size. But, luckily this is only really applied to Hawaiian breaks.

I definitely prefer the standard measurement method.

4. Swell Rating

Now, for the quickest way of understanding how good the waves are, look at the swell rating given in stars.

The number of solid stars (darker blue) reflect the power and size of the swell. There can be a minimum of one solid star and a maximum of five solid stars.As you can see below in image 8 we have a forecast with one solid star so not the best.

The number of faded stars (lighter blue) is where the original swell rating would have reached if all other factors were good. Usually, if there are any faded stars it’s because the wind conditions have downgraded the original swell rating.

For example, if we now look in the wind column in image 8 (above), the gust speed in red is pretty high at 33kph. This was the likely reason why the original two star rating was downgraded to a one star rating.

Personally, I don’t head to the coast for anything below a solid two star rating.

5. Primary Swell vs Secondary Swell

Now, if you’re not familiar with a surfing swell it’s basically what we call the waves arriving along a coastline.

On the surf report, we have a ‘Primary Swell’ and a ‘Secondary Swell’ – but what do these mean? I’ll quickly explain…

Because the worlds oceans are so vast, a coastline can have more than one swell heading towards it at one time.

The title ‘Primary swell’ is given to the swell with the most potential to reach a coastline. Therefore a ‘Secondary swell’ is the swell with the second most potential to reach the chosen coastline. This is also the same with the ‘Third’ and ‘Fourth’ swells, but we don’t care too much about those.

To understand which swell has the best potential to reach a coastline, we look at three things; swell period, swell direction and swell height… we’ll go through each area in the next bit.

6. Swell Period

One of the first things to check when looking in the primary swell column is the swell period (image 10).

In short, the swell period is basically the amount of time between each wave. The longer the time, the more surfable the waves. This is often overlooked but is one of the best things to understand when learning how to read a surf report.

As ’12s / 12 seconds’ doesn’t give you a very good idea, I’ve attached a small blurb for the most common swell periods…

• 1-4 seconds – Surfboard stays in the bag
• 5-6 seconds – Still not great
• 7-9 seconds – Only go if you’re desperate
• 10-12 seconds – Promising ground swells
• 13-15 seconds – Get down the coast
• 16+ seconds – The most powerful swells

Anything with a swell period over 10 seconds is typically referred to as a ground swell. These are much better conditions to surf in as these ground swells create a visible, organised lineup. They also have a smaller chance of being negatively effected by local wind conditions.

Whereas swell periods under 10 seconds are typically referred to as wind swells. These result in mushy conditions without a visible, unorganised lineup of waves. Wind swells also commonly come with unfavourable wind conditions as they’re often not powerful enough to escape the storm that created them.

So that’s the first area that contributes to swell potential, next up is swell direction.

7. Swell Direction

Onto swell direction, which is the arrow in the primary swell column. The exact swell direction can be found by clicking on this swell direction arrow, like shown in image 11 (below).

Now, a ‘good’ swell direction completely depends on where you’re planning to surf and generally speaking you want it to be heading directly at the coastline.

This does mean that each surf location will have it’s own optimal swell direction…

Take Woolacombe, UK as the first example – image 12 below shows that the optimal swell direction (big arrow) is West North West (WNW). You’ve also got some slightly less optimal swell directions (smaller arrows) of North West (NW) and West South West (WSW). All of these swell directions fall within the beach’s ‘Swell Window’.

If the swell direction is within the swell window, surfable waves are more likely to occur.

So, lets take a look at another beach in the UK, Bantham.

As image 13 (below) shows, Bantham would much rather a South South West (SSW) swell direction for the best chance of good waves.

Hopefully, this outlines why every surf location has it’s own unique surfing parameters that allow it to produce (or not produce) decent waves.

8. Swell Height

The final area that contributes towards swell potential is swell height, highlighted with the dotted green outline in image 14 (below).

The first thing to note is that swell height is NOT the same as wave height… but there is a correlation between the two.

The swell height is typically the average of the largest third of all waves. Now, to make that a bit easier to digest, imagine nine waves;

• 2ft x 3
• 3ft x 3
• 4ft x 3

The swell height for these nine waves would be 4ft as that’s the average of the largest third (4ft x 3).

As a rule of thumb the largest wave within a swell will be 1.5x the swell height. So, if we use our 4ft swell example again, the largest wave height in this 4ft swell is likely to be around the 6ft mark.

9. Wind

Moving onto the second to last column on the surf report, wind.

Ideally, us surfers are perfectly happy with little to no wind. It makes forecasting a bit easier and means a swell can crack on with being a swell.

But as wind is sometimes a thing, it’s helpful to understand how its speed and direction effect surfing conditions. For that reason, let’s take a look at ‘Wind Speed’, ‘Wind Direction’ and ‘Onshore vs Offshore Winds’.

10. Wind Speed

On the surf report we’ve got two numbers in the wind column, a big one in bold and a smaller one followed by kph (kilometers per hour). The big number is the steady wind speed and the small number is the gust wind speed.

Out of these two numbers, pay more attention to is the gust wind speed. High gust wind speeds can make a swell slightly more unpredictable when waves are breaking and they also make it harder to stand up.

As a personal preference, I stay away from any steady wind speed over 20kph and gust speeds over 35kph.

11. Wind Direction

Now, onto the more important part of wind when learning how to read a surf report – wind direction.

The first thing to note is that (just like swell direction) a favourable wind direction is completely dependent on where you’re surfing.

When surfers talk about wind direction they normally talk about two things onshore and offshore winds. They’re easily mixed up but one is bad news for surfing and one is good news for surfing.

Let’s take a look at both and the differences between them.

12. Onshore vs Offshore winds

Onshore winds (Bad for surfing)

• Winds that blow from the sea towards the beach
• Force waves to break very early so there is less chance of green waves
• Create small choppy waves mixing with incoming swells for a messy lineup
• Effect gently sloping beaches the most, steeper beaches and reef breaks can handle them a little better
• Only enjoyed by surfers performing aerials to help their surfboards stick to feet in the air

Offshore winds (Good for surfing)

• Winds that blow from the beach towards the sea
• Next best option to no wind at all
• Helps remove surface chop to create a ‘glassier’ lineup
• Slows the time it takes for a wave to break creating everyones favourite green waves
• Easier to paddle ‘out the back’ of a set

In magicseaweeds’ surf report, the wind direction is visible by hovering over the arrow in the wind column (image 16, above). It also gives an indication of the wind speed strength (Moderate) and exact wind coordinates (ESE – 118°).

Generally speaking, you want your wind direction going in the exact opposite direction as your swell direction (providing the swell direction is good) for the best conditions.

The colour of the arrow background is a quick glance traffic light system;

• Green = Good,
• Amber = Average,
• Red = Not good

13. Weather

The penultimate column on our surf report is probably the most familiar looking part of the surfing forecast table – the weather.

The icons are standard weather icons and the air temperature is also provided.

If you’re anything like me, this column is the last thing I check as I’m only interested in what the waves are doing… but it’s useful for those who need it.

14. Probability

The final column in our surf report is the probability. This is the measurement of whether or not everything that has been forecasted will actually happen.

Image 18 (above) shows a probability of 100%, but this is because I was forecasting the same day as I pulled this image from the site.

The further you look into the future the lower the probability will be as forecasting becomes more difficult.

So, if you’re looking at a five star swell a couple of weeks from now… take it with a pinch of salt.

15. Other Factors to Consider

Hopefully, the info so far has moved your surfing forecast status from beginner to seasoned guru – but there’s other factors to consider outside of the surf report.

Let’s quickly take a look at the three big hitters that also play a part in forecasting great waves…

1. The Time of Year

In the UK (especially in the Spring) there is a thing called a ‘Convection Sea Breeze’.

This is where the land/beach is hotter than the sea in the morning. This creates a favourable convection sea breeze that simulates a slight offshore wind. However, as the sea warms up throughout the day these convection sea breezes disappear.

This is one of the reasons you often get glassy green waves in the morning and a messy lineup in the afternoon. Not an issue per se but another thing to be aware of.

2. Local Beach Landscape

Knowing how to read a surf report is one thing, but applying that knowledge to a new break you want to surf is another.

If you’re planning a surf sesh it helps to know a little bit about the landscape around the place you’re going to surf. Are there any headlands? Is it within a sheltered cove? Does the beach have a gradual or steep incline?

These types of questions can only really be answered when experiencing the beach in person but play a big part in the types of waves hitting the shore.

3. Water Temperature

Finally, let’s talk about water temperature. In the UK the best swells occur in the Winter months.

So, the question is if you’ve forecasted a decent looking weekend in the middle of January… have you got the wetsuit and accessories to survive it?

Would be a great shame to forecast the swell of the year to only spend half an hour in the water.

Summary

So guys and girls, that is my ultimate guide to ‘How To Read a Surf Report’.

I hope you’ve enjoyed the read and found some of the material useful. If you’ve got any questions feel free to comment them below.

As always, be sure to follow on the usual socials below to keep up to date with the latest surfing content!

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Next read: ‘The 7 Rules of Surfing Etiquette’