Surf Forecasts:
Cable Bay (Porth Trecastell) surf forecast from 16 Aug 2026:
- Most powerful swell: Thursday 20 Aug, 1AM (local time) - 3.5ft (1.1m), 5s period, SW swell with 55 kJ wave energy.
Best Forecast Surf Conditions for Cable Bay (Porth Trecastell) this week:
The most powerful waves expected at Cable Bay (Porth Trecastell) in the next 16 days are 1.1m 5s and forecast to arrive on Thursday (Aug 20) at 1AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.8m 5s period and expected on Friday (Aug 21) at 7AM.
| Wave Type | Time (BST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | - | - |
| Best Surf | - | - |
| Most Powerful | 1AM (Thu 20th Aug) | 3.5ft (1.1m) 5s |
Table - best surf conditions forecast for Cable Bay (Porth Trecastell) over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let’s be straight with you—this run of forecasts for Cable Bay (Porth Trecastell) is a tough one. We’re looking at a long, dry spell with barely a ripple to get excited about for the next couple of weeks. It’s a real test of patience.
The water is sitting at a very unusual 64°F, which is much warmer than normal for this time of year, but that’s about the only thing that’s firing. The combined swell energy is so weak it barely registers—mostly single digits (1 to 32) through the entire outlook, which is about as flat as it gets.
We kick off on Saturday the 15th with a tiny 0.3ft southwest swell and a 12 mph cross-offshore wind. It’s clean, but there’s nothing to ride. Sunday the 16th looks glassy in the morning, but the swell is completely absent. By Monday the 17th, we get a pathetic 1ft of short-period, choppy slop. That’s not surf; that’s a lake with a light breeze. This weak, poor-quality pattern keeps rolling through the whole week. The best we see is a 3ft southwest swell on Wednesday the 19th, but it’s crossed up and messy with onshore winds.
Towards the end of the second week, from about Saturday the 22nd onwards, the wind turns clean offshore (NNE to NE), which is a beautiful sign for the bay. But the swell is cruel—just 0.3ft to 1ft of very long-period groundswell (14 to 15 seconds). That long period would normally mean good shape, but with that tiny height, it’s not going to break. You’ll just see the ocean hump and flatten out. The energy is a whisper (values between 1 and 12).
The only standout, if you can call it that, is Tuesday the 25th. You’ve got a fresh 19 mph offshore wind (NE) keeping the surface like glass, and a whisper of 0.3ft groundswell from the SW. The wave height is too small to surf, but if you’re a beginner or just want to sit on a longboard and feel the ocean, the conditions will be the cleanest of the whole period. Otherwise, honestly, this is a blank run. For a spot that’s usually fairly consistent, a stretch like this is normal enough for this area, but it’s a real bummer.
Rusty.
Short Range ForecastLight rain (total 2mm), mostly falling on Mon night. Very mild (max 18°C on Mon night, min 14°C on Sat night). Winds increasing (calm on Sat night, fresh winds from the S by Mon night). | Days 5-7 Weather SummaryLight rain (total 5mm), mostly falling on Wed night. Very mild (max 17°C on Tue afternoon, min 13°C on Thu night). Wind will be generally light. | |||||||||||||||||||
Sat 15 | Sunday 16 | Monday 17 | Tuesday 18 | Wednesday 19 | Thursday 20 | Friday 21 | ||||||||||||||
PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | AM | PM | Night | |
Swell Height Map |  |  |  |  |  |  |  | |||||||||||||
Wave Height (m) Direction Period (s) | SW 6 | SW 6 | — | — | SW 3 | SW 3 | SW 5 | SW 4 | SSW 5 | W 4 | W 4 | W 4 | SW 4 | SW 5 | SW 5 | SW 6 | SW 14 | WNW 4 | WNW 4 | SW 13 |
Wave Graph  | ||||||||||||||||||||
 kJ | 1 | 1 | 0 | 0 | 2 | 2 | 4 | 34 | 15 | 16 | 9 | 20 | 19 | 55 | 18 | 8 | 8 | 7 | 3 | 7 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | off | glassy | on | cross-on | cross-on | cross-on | on | cross | cross-on | cross | cross-on | cross-on | cross-on | cross | cross | cross-off | cross | cross-off | off |
High Tide | 00:00AM4.50m | 12:25PM3.91m | 00:40AM4.27m | 1:04PM3.73m | 1:21AM3.95m | 1:44PM3.51m | 2:05AM3.58m | 2:29PM3.25m | 2:56AM3.21m | 3:26PM3.00m | 4:05AM2.90m | 4:46PM2.83m | ||||||||
Low Tide | 6:25PM0.02m | 6:55AM-0.16m | 7:05PM0.20m | 7:34AM0.15m | 7:45PM0.46m | 8:13AM0.53m | 8:25PM0.77m | 8:54AM0.92m | 9:10PM1.10m | 9:40AM1.27m | 10:08PM1.38m | 10:45AM1.54m | 11:34PM1.55m | |||||||
 |  |  |  |  | | |  | | | | | |  | | | | | | | |
 | — | — | 5:58 | — | — | 6:00 | — | — | 6:01 | — | — | 6:03 | — | — | 6:05 | — | — | 6:07 | — | — |
 | 8:45 | — | — | 8:44 | — | — | 8:42 | — | — | 8:39 | — | — | 8:37 | — | — | 8:36 | — | — | 8:32 | — |
mm | — | — | — | — | — | — | — | 2 | — | — | — | — | — | 5 | — | — | — | — | — | — |
Temp °C | 15 | 14 | 15 | 16 | 16 | 15 | 16 | 18 | 16 | 17 | 17 | 16 | 16 | 16 | 15 | 15 | 14 | 14 | 16 | 15 |
Feels °C | 11 | 11 | 14 | 13 | 14 | 14 | 13 | 16 | 12 | 14 | 14 | 11 | 12 | 14 | 12 | 13 | 13 | 11 | 13 | 11 |
Swell 1 Height (m) Direction Period (s) | SW 6 | N 3 | — | — | SW 4 | SW 3 | SW 5 | — | SSW 5 | — | — | SW 6 | NW 4 | SW 16 | SW 5 | SW 6 | SSW 5 | N 5 | WNW 4 | N 5 |
| kJ | 1 | 1 | — | — | 1 | 2 | 4 | — | 15 | — | — | 2 | 6 | 10 | 18 | 8 | 3 | 11 | 3 | 11 |
Swell 2 Height (m) Direction Period (s) | — | SW 6 | — | — | — | SW 5 | SW 5 | — | — | S 16 | W 17 | SW 16 | S 15 | — | SW 15 | SW 14 | SW 14 | SW 5 | NNW 4 | SW 13 |
| kJ | — | 1 | — | — | — | 1 | 4 | — | — | 5 | 6 | 10 | 5 | — | 8 | 8 | 8 | 1 | 3 | 7 |
Swell 3 Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | SW 14 | SW 5 | — |
| kJ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 7 | 1 | — |
Wind waves Height (m) Direction Period (s) | NNW 4 | — | — | — | SW 3 | NW 3 | NW 3 | SW 4 | NW 4 | W 4 | W 4 | W 4 | SW 4 | SW 5 | NW 4 | NNW 4 | N 4 | WNW 4 | — | NE 3 |
| kJ | 5 | — | — | — | 2 | 1 | 3 | 34 | 13 | 16 | 9 | 20 | 19 | 55 | 16 | 6 | 3 | 6 | — | 2 |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 333 | 256 | 256 | 259 | 221 | 258 | 297 | 574 | 329 | 580 | 187 | 284 | 256 | 244 | 185 | 363 | 157 | 172 | 211 | 180 |
Best forecast wave conditions in Anglesy | ||||||||||||||||||||
Best forecast wave conditions in United Kingdom | ||||||||||||||||||||
Header Global | ||||||||||||||||||||
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Information about the Cable Bay (Porth Trecastell) Surf forecast
The above surf forecast table for Cable Bay (Porth Trecastell) provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Cable Bay (Porth Trecastell) can be found by selecting the local surf guide option on the grey menu. Our Cable Bay (Porth Trecastell) surf forecast is unique since it includes wave energy (power) that defines the real feel of the surf rather than just the height or the period. If you surf the same spot (Cable Bay (Porth Trecastell)) regularly then make a mental note of the wave energy from the surf forecast table each time you go. Very soon you may start to choose your surf days based on the wave energy alone combined with our forecast of favourable offshore wind conditions. Our star ratings will help here and of course you will also find the usual wave height and period predictions on our surf forecasts as well as a full break down of the swell components under our advanced users option (to reveal that, click the little Einstein character under the tide times).
Further information to help with frequently asked questions about our surf forecast for Cable Bay (Porth Trecastell) may be found under the help tab on the top menu and also by moving your mouse over the question marks on the surf forecast table itself. Please always bear in mind that the forecast is for near-shore open water and local factors at each surf break influence the actual breaking wave height, such as the beach / reef profile, water depths offshore and shelter.
Are you planning a holiday in Anglesy? If you are looking for accommodation near Cable Bay, camping, hotels and holiday cottages in Anglesy, consider staying in Anglesey which is 4 km (2 miles) away. Other places in and around Anglesy where you can find information about places to rent, and car hire include Holyhead which is 14 km (9 miles) away, Bangor, Porthmadog and Llandudno.
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