Surf Forecasts:
Monabe Rivermouth surf forecast from 16 Aug 2026:
- Best quality surf: Friday 21 Aug, 3AM (local time) - 5.5ft (1.7m), 11s period, S swell with cross-offshore winds.
- Most powerful swell: Friday 21 Aug, 6AM (local time) - 6ft (1.8m), 11s period, S swell with 804 kJ wave energy.
- Next surfable swell (1★+): Monday 17 Aug, 9AM (local time) - 4ft (1.2m), 9s period with ESE 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 (Aug 17) at 9AM. The primary swell is predicted to be 1.2m and 9s period with a secondary swell of 0.4m and 11s. 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 1.8m 11s and forecast to arrive on Friday (Aug 21) at 6AM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.6m 10s period and expected on Friday (Aug 21) at 3PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9AM (Mon 17th Aug) | 4ft (1.2m) 9s |
| Best Surf | 3AM (Fri 21st Aug) | 5.5ft (1.7m) 11s |
| Most Powerful | 6AM (Fri 21st Aug) | 6ft (1.8m) 11s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright, this is a tough one to start with. Monabe Rivermouth is a very sheltered river-mouth break that rarely breaks at all, so we’re in for a long wait this period. The water temp is sitting at 83°, which is about average for this time of year, nothing to write home about.
For the first several days, from Sunday 16th through to the morning of Thursday 21st, it’s a flat, choppy, or blown-out mess. Swell energy is weak, mostly under 200 (312 is the highest early on, but it’s short-period, wind-affected junk). The wind is mostly cross-on or onshore, and scores are basically zero. Don’t bother paddling out.
Then on the morning of Friday 21st, we get a brief glimmer. Swell jumps to 6ft from the south with an 11-second period, combined energy of 831 (moderate), and glassy conditions. That’s the first real standout of the period – clean, rideable, and the best we’ve seen by far. But it’s only a morning window; the afternoon drops back to nothing.
After that, it goes dead again through the weekend and into Monday 24th. The afternoon of the 24th has a tiny bump of 3ft from the SE with a 13-second period, energy 335, and glassy wind – surfable but very ordinary.
The real standout, and the one to circle on the calendar, is the morning of Tuesday 25th through to the morning of Thursday 27th. Tuesday morning has 5ft from the SE at 14 seconds, energy 845 (moderate), and glassy – that’s clean, punchy, and well-shaped for a river mouth. Wednesday morning steps it up: 7ft SE at 16 seconds, energy 2013 (strong), glassy, and the forecast says “very good surf conditions.” Thursday morning is the crown jewel: 8ft SE at 16 seconds, energy 3538 (strong), glassy – but that’s getting into expert territory, especially with a long-period groundswell that might make the rivermouth a bit walled. Still, if you’re skilled, that’s a session to remember.
Friday 28th morning sees a big 10ft swell from the SSE at 16 seconds, energy 4878 (strong), but it’s cross-off wind from the ENE, so it’s clean but huge – only for experts. The afternoon gets messy with 19 mph cross-shore winds. After that, it’s a blown-out, dangerous mess from Saturday 29th onward, with 13ft to 20ft swells and near-gale winds. The only late highlight is Monday 31st morning: 13ft from the east at 15 seconds, glassy, energy 6985 (very strong) – an excellent, clean, massive swell for experienced surfers only.
Bottom line: the first week is mostly a write-off. The best windows are Friday 21st morning, then the standout stretch from Tuesday 25th morning through Thursday 27th morning, with Monday 31st morning as a late, expert-only gem. For most of us, aim for the 25th to 27th.
Rusty
Short Range ForecastModerate rain (total 10mm), heaviest on Sun afternoon. Warm (max 29°C on Wed morning, min 24°C on Tue night). Wind will be generally light. | Days 5-7 Weather SummaryLight rain (total 6mm), mostly falling on Sat morning. Warm (max 29°C on Thu morning, min 24°C on Sat morning). Wind will be generally light. | |||||||||||||||||||
Sun 16 | Monday 17 | Tuesday 18 | Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | ||||||||||||||
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) | ESE 6 | ESE 6 | ESE 9 | ESE 9 | ESE 9 | ESE 8 | ESE 8 | ESE 8 | E 8 | ESE 8 | ESE 8 | S 9 | S 9 | S 11 | S 11 | SE 11 | SE 11 | E 9 | E 8 | E 10 |
Wave Graph | ||||||||||||||||||||
170 | 176 | 242 | 172 | 113 | 82 | 73 | 72 | 64 | 83 | 58 | 106 | 117 | 546 | 776 | 30 | 30 | 38 | 20 | 47 | |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross | cross-off | on | cross-off | glassy | cross-on | glassy | glassy | on | cross-off | glassy | on | glassy | glassy | on | glassy | cross-off | cross | on |
High Tide | 8:19PM1.79m | 8:33AM1.68m | 8:43PM1.73m | 9:16AM1.53m | 9:06PM1.67m | 10:07AM1.38m | 9:29PM1.59m | 11:21AM1.24m | 9:56PM1.50m | 2:33PM1.21m | 10:41PM1.41m | 4:35PM1.33m | 00:46AM1.36m | |||||||
Low Tide | 2:28AM0.48m | 2:33PM0.56m | 3:05AM0.49m | 2:58PM0.75m | 3:46AM0.54m | 3:21PM0.92m | 4:36AM0.61m | 3:41PM1.08m | 5:50AM0.67m | 3:45PM1.21m | 7:39AM0.66m | 8:21PM1.28m | ||||||||
— | — | 5:26 | — | — | 5:28 | — | — | 5:28 | — | — | 5:28 | — | — | 5:30 | — | — | 5:31 | — | — | |
6:51 | — | — | 6:49 | — | — | 6:47 | — | — | 6:46 | — | — | 6:45 | — | — | 6:45 | — | — | 6:44 | — | |
mm | 4 | 4 | 1 | — | — | — | 1 | — | — | — | — | — | 1 | — | — | — | — | 5 | 12 | 90 |
Temp °C | 27 | 25 | 28 | 28 | 26 | 28 | 28 | 26 | 29 | 28 | 26 | 29 | 28 | 26 | 29 | 29 | 26 | 24 | 25 | 26 |
Feels °C | 29 | 28 | 31 | 30 | 31 | 31 | 31 | 30 | 32 | 31 | 31 | 32 | 31 | 31 | 32 | 32 | 30 | 27 | 28 | 28 |
Swell 1 Height (m) Direction Period (s) | S 9 | S 8 | S 8 | S 8 | ESE 9 | ESE 8 | ESE 8 | ESE 8 | E 8 | SE 10 | ESE 8 | S 9 | S 9 | S 11 | S 11 | S 10 | SSW 10 | SSW 10 | SSW 10 | SSW 9 |
76 | 50 | 33 | 32 | 113 | 82 | 73 | 72 | 64 | 25 | 58 | 106 | 117 | 546 | 776 | 573 | 394 | 356 | 348 | 287 | |
Swell 2 Height (m) Direction Period (s) | ESE 10 | SE 11 | SE 11 | SE 11 | S 8 | SSW 8 | SSW 8 | SSW 7 | SE 10 | SSW 8 | SE 10 | E 7 | E 7 | ESE 7 | SE 11 | E 9 | E 8 | E 9 | E 8 | E 10 |
35 | 31 | 30 | 30 | 29 | 19 | 19 | 18 | 26 | 11 | 26 | 39 | 26 | 17 | 30 | 24 | 20 | 38 | 18 | 47 | |
Swell 3 Height (m) Direction Period (s) | E 10 | — | — | SE 11 | SE 11 | SE 11 | SE 11 | SE 10 | SSW 7 | SW 9 | SSW 8 | ESE 10 | ESE 10 | ESE 10 | E 9 | SE 11 | SE 11 | SE 11 | ESE 10 | ESE 13 |
31 | — | — | 30 | 30 | 30 | 29 | 16 | 11 | 3 | 11 | 39 | 39 | 42 | 25 | 30 | 30 | 29 | 20 | 32 | |
Wind waves Height (m) Direction Period (s) | ESE 6 | ESE 6 | ESE 9 | ESE 9 | — | — | — | — | — | ESE 8 | — | — | — | — | — | — | — | — | — | — |
170 | 176 | 242 | 172 | — | — | — | — | — | 83 | — | — | — | — | — | — | — | — | — | — | |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 20 | 20 | 0 | 387 | 9 | 9 | 50 | 9 | 9 | 578 | 9 | 9 | 50 | 0 | 0 | 230 | 9 | 9 | 20 | 284 |
Best forecast wave conditions in Shikoku | ||||||||||||||||||||
Best forecast wave conditions in Japan | ||||||||||||||||||||
Header Global | ||||||||||||||||||||
- Map Icons:
Break
Live Wave Height (m)
Live Wind Speed (km/h)
Surf Rating (10 Max)
Ocean Swells (m)
Wind Speed (km/h)
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.











