Surf Forecasts:
Monabe Rivermouth surf forecast from 12 Sep 2026:
- Best quality surf: Saturday 19 Sep, 9PM (local time) - 16ft (5.0m), 15s period, ESE swell with offshore winds.
- Most powerful swell: Saturday 19 Sep, 9PM (local time) - 16ft (5.0m), 15s period, ESE swell with 11,949 kJ wave energy.
- Next surfable swell (1★+): Monday 14 Sep, 12AM (local time) - 3.5ft (1.0m), 8s period with SE swell.
Best Forecast Surf Conditions for Monabe Rivermouth this week:
The surf forecast for Monabe Rivermouth over the next 16 days: The first swell (rated 1 star or higher) is forecast to arrive on Monday (Sep 14) at 12AM. The primary swell is predicted to be 1.0m and 8s period with a secondary swell of 0.5m and 13s. The wind is predicted to be cross-offshore as the swell arrives.
The most powerful waves expected at Monabe Rivermouth in the next 16 days are 5.0m 15s and forecast to arrive on Saturday (Sep 19) at 9PM. Winds are predicted to be offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.6m 4s period and expected on Thursday (Sep 17) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 12AM (Mon 14th Sep) | 3.5ft (1.0m) 8s |
| Best Surf | 9PM (Sat 19th Sep) | 16ft (5.0m) 15s |
| Most Powerful | 9PM (Sat 19th Sep) | 16ft (5.0m) 15s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright, Rusty here. Let’s break down the next couple of weeks at Monabe Rivermouth.
Honestly, it’s a bit of a slow start. The first real window we’ve got is Monday morning, the 14th. There’s a tiny 4ft swell out of the ESE, with a period of 8 seconds. It’s not much to get excited about—just ordinary, surfable waves. The glassy conditions will make it look prettier than it is, but combined energy is only moderate at 243. We see similar glimmers on Tuesday morning and Wednesday morning, but the wave quality just isn’t there yet.
The real story, and the standout of the entire forecast, lands on Saturday the 19th. That morning, we’re looking at a 7ft ESE groundswell with a very long 17-second period. The combined energy jumps to a massive 4481. It’s glassy, clean, and the wind is calm. This is excellent surf for experienced surfers—the kind of day you call in sick for. The long period means this river mouth setup should produce some proper, well-shaped waves with plenty of energy, though the sets will be spaced out. If you’re not an expert, the 10ft that rolls in that afternoon and the 13ft on Sunday morning will be too much.
That quality carries right into Monday the 21st. We see the biggest raw numbers of the whole run: a 21ft SE swell at 14 seconds in the morning, with combined energy hitting 16102. The wind is clean and cross-offshore. This is a big, powerful, expert-only swell. The afternoon gets a bit messy with a cross-shore wind, so stick to the early session.
After that, it’s a dramatic drop-off. By Tuesday the 22nd, onshore winds and a tiny 2ft swell ruin any chance of a wave, and that continues for several days. We get a bit of a tease on Sunday the 27th with a 6ft average swell, but then Monday the 28th morning delivers one more late-summer gift: a 7ft SSE groundswell with a 14-second period. Combined energy is a strong 3394, and it’s clean with offshore wind. That’s your final pick of the bunch.
So, if you’re an experienced surfer, circle Saturday the 19th and Monday the 21st. For everyone else, Monday the 14th or Tuesday the 15th mornings offer the most forgiving, glassy conditions, even if the waves themselves are only ordinary.
Rusty.
Short Range ForecastLight rain (total 9mm), mostly falling on Sun morning. Warm (max 28°C on Sun morning, min 23°C on Mon night). Wind will be generally light. | Days 5-7 Weather SummaryModerate rain (total 19mm), heaviest on Thu afternoon. Warm (max 27°C on Fri morning, min 23°C on Tue night). Wind will be generally light. | ||||||||||||||||||
Sunday 13 | Monday 14 | Tuesday 15 | Wednesday 16 | Thursday 17 | Friday 18 | ||||||||||||||
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) | E 14 | E 13 | ESE 13 | SE 8 | ESE 8 | SE 8 | SE 9 | ESE 10 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | E 8 | E 7 | E 8 | E 9 | E 9 |
Wave Graph  | |||||||||||||||||||
 kJ | 96 | 85 | 257 | 138 | 188 | 158 | 253 | 307 | 255 | 199 | 165 | 121 | 162 | 131 | 144 | 494 | 634 | 759 | 635 |
Wind (km/h) | |||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | glassy | glassy | on | cross-off | glassy | on | cross-off | glassy | on | cross-off | glassy | cross-on | cross-off | glassy | glassy | cross-off | glassy | on | cross-off |
High Tide | 6:55AM1.89m | 7:06PM1.85m | 7:33AM1.81m | 7:27PM1.81m | 8:10AM1.69m | 7:49PM1.75m | 8:48AM1.55m | 8:09PM1.68m | 9:32AM1.40m | 8:30PM1.59m | 10:36AM1.27m | 8:52PM1.49m | |||||||
Low Tide | 00:46AM0.35m | 1:01PM0.39m | 1:18AM0.30m | 1:29PM0.54m | 1:49AM0.31m | 1:53PM0.70m | 2:22AM0.36m | 2:16PM0.85m | 2:58AM0.44m | 2:36PM0.99m | 3:41AM0.56m | 2:51PM1.11m | |||||||
 |  |  |  | |  |  | | |  | | | |  | | | | | | |
 | — | 5:46 | — | — | 5:46 | — | — | 5:47 | — | — | 5:48 | — | — | 5:48 | — | — | 5:48 | — | — |
 | 6:15 | — | 6:15 | — | — | 6:14 | — | — | 6:12 | — | — | 6:10 | — | — | 6:08 | — | — | 6:07 | — |
mm | 1 | 2 | — | — | — | — | 6 | — | — | 1 | 1 | 2 | 3 | 4 | 6 | 1 | — | 1 | — |
Temp °C | 26 | 28 | 28 | 25 | 28 | 28 | 25 | 26 | 26 | 24 | 26 | 25 | 24 | 26 | 26 | 24 | 27 | 27 | 24 |
Feels °C | 31 | 32 | 32 | 29 | 31 | 31 | 29 | 28 | 28 | 27 | 30 | 28 | 28 | 29 | 31 | 27 | 29 | 30 | 27 |
Swell 1 Height (m) Direction Period (s) | E 14 | ESE 9 | ESE 13 | SE 8 | ESE 8 | SE 8 | SE 9 | ESE 10 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | E 12 | E 15 | S 11 | S 10 | ESE 20 |
| kJ | 96 | 48 | 257 | 138 | 188 | 158 | 253 | 307 | 255 | 199 | 165 | 121 | 162 | 131 | 25 | 4 | 2 | 2 | 160 |
Swell 2 Height (m) Direction Period (s) | S 7 | E 13 | S 7 | E 13 | E 13 | E 12 | E 12 | E 14 | E 14 | E 14 | E 14 | E 13 | E 13 | E 12 | S 7 | S 6 | — | — | S 9 |
| kJ | 23 | 85 | 8 | 82 | 52 | 73 | 68 | 37 | 57 | 57 | 63 | 51 | 53 | 26 | 1 | 1 | — | — | 7 |
Swell 3 Height (m) Direction Period (s) | ESE 9 | S 7 | SE 9 | S 6 | S 7 | S 7 | S 7 | E 12 | S 6 | S 7 | S 7 | S 7 | S 6 | S 7 | S 7 | S 6 | — | — | — |
| kJ | 33 | 14 | 13 | 3 | 3 | 4 | 4 | 11 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | — | — | — |
Wind waves Height (m) Direction Period (s) | E 5 | — | ENE 6 | — | — | — | — | — | — | — | E 3 | E 4 | NE 3 | NE 4 | E 8 | E 7 | E 8 | E 9 | E 9 |
| kJ | 16 | — | 3 | — | — | — | — | — | — | — | 8 | 9 | 3 | 9 | 144 | 494 | 634 | 759 | 635 |
Nearest Offshore or Glassy | |||||||||||||||||||
Distance (km) | 9 | 9 | 50 | 0 | 0 | 42 | 0 | 0 | 75 | 0 | 0 | 47 | 0 | 9 | 9 | 0 | 0 | 20 | 0 |
Best forecast wave conditions in Shikoku | |||||||||||||||||||
Best forecast wave conditions in Japan | |||||||||||||||||||
Header Global | |||||||||||||||||||
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Information about the Monabe Rivermouth Surf forecast
The above surf forecast table for Monabe Rivermouth provides essential information for determining whether the surfing conditions will be good over the next 16 days. A general guide to surfing at Monabe Rivermouth can be found by selecting the local surf guide option on the grey menu. Our Monabe Rivermouth 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 (Monabe Rivermouth) 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 Monabe Rivermouth 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.
Monabe Rivermouth is 11 km (7 miles) from the city of Aki. If you plan a holiday in Shikoku, look for hotels and other accommodation in Aki. Aki has rooms for a wide range of budgets as well as car hire and transport links.
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