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So guys, one of the things I struggled with when I started surfing was understanding how to read a surf report. In this post, I’ll be going through how everything within a surf report works in the hope it will help you guys too.
Some snippets from this ‘How To Read a Surf Report’ guide include how to understand;
- Tidal timings
- Wave height
- Swell rating
- Primary swell vs secondary swell
- Swell direction, swell period and swell height
- Wind direction and wind speed
- Onshore vs offshore winds
- Other factors to consider when forecasting a surfing trip
If any of these sound unfamiliar then this ultimate guide of how to read a surf report post is for you!
I’m based in the UK so I’ll be using a UK based surf forecasting website. One of the best is magicseaweed.com , so I’ll be using examples from them to explain everything.
Now, lets get started…
The Tidal Chart
Starting with the easier stuff, the tidal chart (Image 1). This chart has three main elements and is fairly easy to understand once you get the hang of it.
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).
Fairly simple stuff but hope that all makes sense. Now, for the more complicated bit…
Chart Datum Measurements
The measurements outlined in blue below in image 3 are known as the Chart Datum.
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.
“But what the fudge is it?!” Well 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.
With that, we’ll move onto the last element of this tidal part of the surfing forecast, daylight times.
The final aspect of this chart is 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!
The Surf Report
Now for the more nitty gritty stuff, the surf report.
The stuff we’ve discussed so far has been about what the tide is doing and when its happening but not too much about what the waves are doing. This section 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.
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. 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.
Now, if you don’t really fancy learning how to read a surf report you can look at the swell rating. Seems fairly obvious but there’s a couple things about this rating you may not know…
The first is the number of solid stars. These actually 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 second part most people don’t know is what the number of faded stars mean. Their purpose is to actually downgrade the initial solid star swell rating depending on whether or not the wind conditions are favourable. So, the forecast shown in image 8 used to have a solid two star rating but was downgraded to a one star rating due to unfavourable wind conditions. If you then look in the wind column the gust speed in red is pretty high at 33kph. This was the likely reason why the original two star rating was downgraded.
It’s hard to give recommendations on the minimum star rating to head out for is because everyone’s situation is different. But, personally I don’t head out for anything below a solid two star rating. The conditions for a solid two star rating would suite most experience levels and provide enough fun waves for a trip to be worth the effort.
Primary Swell vs Secondary Swell
Now, you may have been wondering “Why is there a primary swell and a secondary swell column on the surf report?” Or “What is the difference between the primary swell and the secondary swell?”. I’ll quickly explain…
The worlds oceans are vast. This means they can be affected by varying winds creating multiple swells within relatively small areas. This then leads to more than one swell travelling towards the same coastline within the same time period.
The title primary swell is given to the swell with the most potential to reach the chosen coastline. The title of secondary swell is given to the swell with the second most potential to reach the chosen coastline. The third with the third most potential and so on.
The best swell potential is determined by assessing the three elements that make up a swell; the swell period, swell direction and swell height which we’ll go through next.
So we know a primary swell is determined by its swell period (also known as swell timing), swell direction and swell height. But what do each of these things mean?
One of the first things to check when looking in the primary swell column is the swell period as shown below in image 10. This is often overlooked but is one of the best things to understand when learning how to read a surf report.
In short, the swell period is basically the amount of time between waves. The longer the time, the more surfable the waves.
As “12s” on its own doesn’t really help, here are a few easy time brackets to group swell periods;
1-4 seconds (Surfboard stays in the bag)
- Pretty much never surfable
- Created in the very early stages of strong winds
- Not powerful enough to travel away from the storm that created them
- Often come with very strong local winds attached
5-6 seconds (Still not great)
- Similar to the above but you’ll see the occasional wave face
- Still not powerful enough to escape the storm that created it
- Still likely to come with strong onshore winds making for a mushy surfing mess
7-9 seconds (The starting point)
- Good surfable waves are still dependent on favourable local conditions.
- Waves will still be quite close together
- Still not offering much in terms of wave power
- Fairly unorganised lineup
- Waves will be smaller in height than the swell that created them
10-12 seconds (Promising ground swells)
- More likely to offer consistently good surfing conditions
- They’re strong enough to break away from the storm that created them
- Will be able to create a visible lineup of organised waves
- The waves are likely to be equal in height to the swell that created them
13-15 seconds (Get down the coast)
- Created a considerable distance from the shoreline by powerful storms.
- Able to reach beaches without the storm that created them so surfers can have both great waves and great weather conditions
- Can bend and refract around headlands to reach more sheltered coves
- A definitive wave lineup can be seen when compared to any of the swell periods previously discussed
- Bigger in height than the swell that created them, large waves expected
16+ seconds (The most powerful swells)
- These waves are created by the most powerful storms
- They can travel the length and breadth of the biggest oceans to reach coastlines
- Waves can be considerably bigger than the swell that created them
- The most sheltered coves could expect to see some action
So, I’m hoping these swell period brackets above help to give a better picture of the waves given in the forecast. Out of all the brackets I’ve mentioned, anything with a swell period over 10 seconds (typically referred to as a ground swell) offers a much better chance of producing good surfable waves when compared to swell periods under 10 seconds (typically referred to as a wind swell).
But, there are still two other areas left to consider when searching for decent waves; swell direction and swell height.
The next thing to take a look at is the 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.
Now, a good swell direction is much more dependent on where you’re planning to surf and I’ll explain why using images 12 and 13 below.
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’ (Dotted line).
The swell window basically means that any swell direction within this window will help towards good surfing conditions, with the best being the optimal swell direction. If the swell direction is not within the swell window it’s much less likely any surfable waves will occur.
So, lets take a look at another beach in the UK, Bantham. As image 13 shows, the optimal swell direction is completely different to that of Woolacombe. Bantham would much rather a South South West (SSW) swell direction for the best chance of good waves.
This hopefully outlines why the location of where you’re going to be surfing can make a big difference on whether or not the swell direction will help produce good waves or not.
The final thing to consider when looking at a swell is the swell height, highlighted with the dotted green outline in image 14. 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; 3x 2ft, 3x 3ft and 3x 4ft. The swell height for these nine waves would be 4ft as that’s the average of the largest third (3x 4ft).
Just to be sure I’ll say it again – the swell height is an average. 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.
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.
So, in the wind column we’ve got two numbers, a big one and a small one followed by kph. The big number is the steady wind speed and the small number is the gust wind speed.
Magicseaweed.com give both measurements in knots per hour (kph) but some surf reports use miles per hour (mph), the numbers are fairly similar with 1kph = 1.15mph.
Out of these two numbers the one to pay most 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.
There’s no official rule of thumb when it comes to the question of – how windy is too windy to go surfing? But as a personal preference, I stay away from any steady wind speed over 15kph / 17mph and gust speeds over 20kph / 23mph.
Now, onto the more important part of the wind when learning how to read a surf report, the wind direction. The first thing to note is that a favourable wind direction completely depends on where you’re surfing. This therefore makes it very similar to our friend swell direction that we covered in point 4.2 above (feel free to refresh your memory if you want).
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.
What is the difference between onshore and offshore winds?
Onshore winds (Bad news 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 news 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 the surf report we can easily check whether the wind is onshore or offshore by hovering over the big arrow in the wind column as shown in image 16. It will also give 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 with green = good, amber = ok, red = not good.
Not important enough for its own column name but is something you want to check before planning a session. This is also probably the most familiar looking part of the surfing forecast table.
The icons are standard weather icons and the air temperature is also provided. I’d advise doing your own weather research in a bit more depth before heading out, but these are useful at a glance.
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 shows a probability of 100%, but this is because I was forecasting the same day as I searched. As you look further into the future the surfing forecast probability will start to decrease as things become less certain. So, if you’re looking at a pumping 15 second swell period and favourable wind conditions in a couple of Saturdays… take it with a pinch of salt.
Other Things to Consider
Although learning how to read a surf report can help you plan a great surfing sesh, there are a few things not on the report you may also want to consider.
The Time of Year
In the Spring in the UK there are things called ‘Convection Sea Breezes’. This is where the land is hotter than the sea in the morning creating a favourable convection sea breeze similar to slight offshore winds. But, as the sea warms up throughout the day these favourable convection sea breezes disappear.
This is why you often get glassy green waves in the morning and a messy lineup in the afternoon. Not a massive issue but another thing to be aware of.
Local Beach Landscape
Learning how to read a surf report is one thing but being able to apply it to the beach you want to surf at is another. If you’re planning a surf sesh it helps to know a little bit about 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 will only really be answered when experiencing the beach in person but can impact the types of waves to expect.
In the UK the best swells are more likely to 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 thickness and accessories for it? Would be a shame to put all that effort of forecasting in to only spend half an hour in the water.
That’s it guys, my ultimate guide of ‘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.
Also, be great if you could check me out on my other social media channels and let me know what you think!
Next read: ‘The 7 Rules of Surfing Etiquette’
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