Tides… wind… waves… and what to be aware of

Helen has been paddling for over ten years, and is a qualified oceanographer

Words: Helen Trehoret
Photos: Helen Trehoret and the RNLI

Helen is the owner of Barrachou Paddle, based in North Finistère, France. Helen has been paddling for over ten years, and is a qualified oceanographer, graduating for Plymouth University and working as an oceanographer before opening her SUP business in France. https://barrachousup.com

The SUP industry is booming; more and more people are taking to the water; the surge in popularity is highlighting just how accessible our sport has become. The beauty of SUP is that it is easy to get the basics, learning paddling and turning is a quick session. However, the more challenging aspect of our sport is the planning and the ability to read a forecast, then relating this to actual local conditions.

The three factors that paddlers must consider when planning a paddle session are:

  • Tides
  • Waves, and
  • Wind.

Depending on what you are doing in the session will determine which factor will be more critical. Aimed at beginners, this article will investigate the three factors that can make or break a session, highlighting what paddlers should be aware of when planning a session.

Paddling in the UK, Ireland or any spot on the north Atlantic coastline is subject to significant changes in tidal conditions. The worlds largest tidal range, measuring 16 metres is in the Bay of Fundy, Canada. However, the second biggest takes place in the Severn Estuary. This makes it vitally important for UK paddlers to understand the implications of the tidal cycle.

Tides are part of a cycle consisting of Springs and Neaps, causing the tidal range to grow and shrink alternatively twice during every 28 days. Predicting the tidal differences in your area can be done using tide tables, these have the times of the low and high tide.

So we will know exactly what time is high and low tide, but we will also need to know where the water will be in two and a half hours after high tide. We do this by the rule of twelfths.

Rule of twelfths
The rule of twelfths takes the time between the low and high tide, for example, 10m, divides it by 12, giving a value of 0.83. The rule of twelfths tells us that in the first hour after low tide the water will rise one-twelfth of its range, in this case, it is 0.83, then in the second hour 0.83×2 = 1.66 and then in its third hour it will rise three twelfths 0.83×3 = 2.49, so at the end of the third hour, it will have increased 4.98m.

Why bother with this? If the phase of the moon is in spring tides, then you will see that the value in the rule of twelfths at mid-tide is bigger than at neap tides. This is when we need to plan our paddle session wisely. Paddling up the estuary at this point would be fruitless, you will be paddling against the current, a strong current, again depending on your location.

Tidal curves
But in the age of the smartphone and internet we don’t need to be mathematicians to predict the tidal range, we have online tidal curves. The shape of the graph will depend on the location and the phase of the moon.

The graph will be steeper and more pronounced with spring tides and flatter with the neap tides. They are showing precisely that in spring tides the movement of water is exaggerated.

The location of your paddle session depends on the effect of the tide. In some places, there is only one tide a day (Diurnal) and two in other locations (semi-diurnal). Typically, in the UK we have semi-diurnal, meaning there are two tides each day.

The morphology of the UK, with channels, estuaries, peninsulas means that as the tide pushes up channels, some tidal ranges get bigger. For example, the Bristol Channel has one of the biggest tidal ranges in the UK, with the Solway Firth second.

Interestingly, Southampton has a famous double tide at spring tides and a very rapid decrease in-depth during the ebb. The double high tide in the Solent is caused by the incoming sea to take two routes around the Isle of Wight.

Effect of tides on a SUP session
Depending on the type, time and location of the SUP session will determine the need to focus on the tide. For SUP surf sessions the neap tides will show minimal movement in the water. So perhaps depending on your spot, your SUP session will last a bit longer than in the spring tide phase of the moon. For long-distance sessions, you will need to know if you are against or with the current, especially at the end of the session!

The wind is either an enemy or friend to SUP paddling; learning to predict the wind can turn a session into a great session or just misery. The type of session that you want to do will determine what the optimal wind speed is. For a downwind session anything under 10 knots is excellent for a beginner session, but the perfect downwind session for intermediate paddlers is over 10 knots and consistently blowing 10 knots.

When planning a SUP surf session wind can be the enemy. If there is wind, offshore is best, cross-shore is tricky, but it can be done if there is an excellent swell period. For touring and for beginners as a rule of thumb, anything under 10 knots is worthy. Most SUP schools are limited to maximal wind speeds, generally around 10 knots. This is when local knowledge comes into play, though it is 10 knots in exposed areas, it is possible to paddle in this where the sea or water is sheltered.

An important rule to follow is to avoid paddling in 10 knots offshore.

Can we predict wind conditions?
After you have unpacked your SUP board, the next thing you need to do is get familiar with wind apps. Windy, Windguru, Windfinder are more popular. These apps generate forecasts based on data produced by numeric models, before launching into your session you need to bear in these are mathematical models, in some places it may be correct, in other areas the model may not work. It is essential to get familiar with the app that is more consistent for your location, the apps cannot see your local terrain, and it is this that can affect the wind flows around your area.

Using Windguru is simple; it has a user-friendly light blue to a dark purple gradient. Generally speaking, blue means that the conditions are flat, calm ranging to purple, which means storm conditions typically.

When looking at the Windguru model, it is essential to note that the data we are given as a free user is less accurate than the data for a fee-paying customer. But the free data service is still a great tool.

Windguru also gives the wind direction, an essential element; this is the difference between being blown offshore or dealing with choppy conditions. Again, the strength of wind depends on your level, type of paddle session and location that you are paddling.
Reading Windguru is simple; it colour-codes conditions to make it even user-friendly. Light blue to green is generally OK for paddlers, pink to purple is a storm, unless you are planning a downwind session then this is not the best conditions to be paddling.
Whatever value you are seeking, it is a rule of thumb to have the wind with you for the end part of your journey or race, when energy levels are more depleted.

Some people enjoy waves; some people are terrified. Whatever your level, you need to be familiar with reading weather apps. Much like what was said in the wind section, each app is different for each spot. MSW, Windty, Windguru or Wisuki can all be used to predict waves.

So, what wave conditions are ideal for paddling?

Wave period
For an epic SUP surf session, anything over one-metre and 10 seconds will be heaven. When we talk about 10 seconds, this is the wave period. Nine seconds and below are typically described as wind swell, excellent in some areas, but not in others. 10-12 seconds and above is normally the swell generated in the open ocean and travel some distance before arriving at your spot.

Wave height
Anything below 0.5m can be described as flat. These are great for flatwater paddling, but SUP surfing maybe a bit challenging. Above 0.5m will see the SUP surfers excited! This also works for lake paddling, depending on the size of the lake or the Loch you will generally see wave heights below one-metre.

Wave direction
This is the most vital factor to investigate, for those facing the Atlantic any swell that comes from the west or the south-west will generate some excellent conditions, the same swell direction will mean that those facing the north or north-west it will be sheltered. How this affects you will depend on the type of session you are planning, if you are ready for a flatwater session then you need to be heading to these more protected breaks, if it’s a SUP surf session, then it will be perfect!

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