
Surf Forecasts:
Monabe Rivermouth surf forecast from 8 Sep 2026:
- Best quality surf: Tuesday 8 Sep, 9PM (local time) - 11ft (3.5m), 10s period, SSE swell with cross-offshore winds.
- Most powerful swell: Wednesday 9 Sep, 3AM (local time) - 11ft (3.5m), 9s period, SSE swell with 2,166 kJ wave energy.
- Next surfable swell (1★+): Tuesday 8 Sep, 9PM (local time) - 11ft (3.5m), 10s period with SSE 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 Tuesday (Sep 08) at 9PM. The primary swell is predicted to be 3.5m and 10s period with a secondary swell of 3.0m and 10s. Another secondary swell of 0.1m and 19s is also forecast. 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 3.5m 9s and forecast to arrive on Wednesday (Sep 09) at 3AM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.3m 6s period and expected on Thursday (Sep 10) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 9PM (Tue 8th Sep) | 11ft (3.5m) 10s |
| Best Surf | 9PM (Tue 8th Sep) | 11ft (3.5m) 10s |
| Most Powerful | 3AM (Wed 9th Sep) | 11ft (3.5m) 9s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright, Rusty here. Let’s have a look at what’s on the table for the next couple of weeks down at Monabe Rivermouth.
Honestly, it’s a bit of a mixed bag, and for the most part, it’s going to be pretty quiet. This break is a river-mouth setup that rarely breaks, so don’t expect much to line up. The first bit of any real interest shows up on Tuesday the 8th of September, with a 6 ft south swell. The water’s sitting at 84°, which is a touch warmer than normal for this time of year. The wind is light and cross-offshore from the ENE, so it’ll be clean. Combined energy is pushing 878, so moderate to strong. That afternoon window is the standout in the whole run—decent size, clean, and the swell direction is spot-on from the south, which is the optimum for this spot. But be aware, it can get a crew down there sometimes.
The following Wednesday morning the 9th sees a bigger 8 ft south swell, but with heavy rain and a cross wind, it’s messy, and honestly not worth paddling out for. The energy is very strong at 1114, but the conditions are ordinary. Wednesday afternoon drops to 6 ft from the SSE with a light cross-off, but still not clean enough to get excited about.
From Thursday the 10th right through to the 15th, we’re looking at small, sub-5 ft swell, mostly from the SE or ESE. A lot of glassy mornings and afternoons, but the wave heights are just too small and weak to do much with. The energy sits between 191 and 364, so the ocean is pretty sleepy. The morning of Friday the 12th has a 3 ft SSE swell with glassy conditions, but it’s just not enough oomph. It’s the kind of run where you’d be better off doing something else.
The swell picks up a tiny bit on Monday the 14th and Tuesday the 15th, with 4 ft to 5 ft from the ESE, and glassy conditions, but the period is short at 8-9 seconds and the energy is still moderate. It’s surfable, but very ordinary. Nothing close to the Tuesday afternoon earlier in the run.
After the 15th, it’s back to tiny surf, below 3 ft for most of the second week, with energy dropping to under 100 by the weekend of the 18th and 19th. The 20th of September shows a little pulse of 4 ft from the E, with glassy conditions, but again, it’s nothing to write home about. The 22nd and 23rd are mostly flat with poor conditions.
So the long and short of it: the only real blip of decent surf is that Tuesday the 8th afternoon. The rest is a long gap of tiny, weak waves. If you’re a beginner, the 6 ft on the 8th is fine, but for the rest, you’re chasing dribble. For a river break that rarely fires, this is pretty normal—expect long gaps. If things look more interesting for kiting than surfing on those days, well, you can figure that out.
Stay safe.
Rusty
Short Range ForecastHeavy rain (total 80mm), heaviest during Tue night. Warm (max 27°C on Tue afternoon, min 22°C on Wed night). Wind will be generally light. | Days 5-7 Weather SummaryModerate rain (total 18mm), heaviest on Sat afternoon. Warm (max 28°C on Sun morning, min 23°C on Sun night). Wind will be generally light. | |||||||||||||||||||
Tue 8 | Wednesday 9 | Thursday 10 | Friday 11 | Saturday 12 | Sunday 13 | Monday 14 | ||||||||||||||
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) | S 9 | SSE 10 | S 9 | SSE 8 | SSE 8 | SE 8 | SE 8 | SE 8 | SSE 8 | SSE 8 | SSE 7 | E 13 | E 14 | E 14 | E 13 | ESE 13 | ESE 9 | ESE 8 | ESE 8 | ESE 9 |
Wave Graph | ||||||||||||||||||||
614 | 1845 | 1108 | 468 | 230 | 158 | 151 | 149 | 126 | 110 | 76 | 88 | 89 | 192 | 85 | 187 | 227 | 192 | 290 | 415 | |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-off | cross-off | cross | cross-off | off | cross-off | glassy | glassy | glassy | glassy | glassy | glassy | glassy | cross-off | glassy | cross-on | cross-off | glassy | glassy | glassy |
High Tide | 4:57PM1.71m | 4:03AM1.71m | 5:26PM1.79m | 4:52AM1.83m | 5:53PM1.84m | 5:36AM1.91m | 6:18PM1.86m | 6:17AM1.93m | 6:43PM1.87m | 6:55AM1.89m | 7:06PM1.85m | 7:33AM1.81m | 7:27PM1.81m | |||||||
Low Tide | 10:32PM0.91m | 10:46AM0.15m | 11:08PM0.74m | 11:25AM0.13m | 11:42PM0.58m | 12:00PM0.17m | 00:14AM0.45m | 12:32PM0.26m | 00:46AM0.35m | 1:01PM0.39m | 1:18AM0.30m | 1:29PM0.54m | 1:49AM0.31m | |||||||
— | — | 5:43 | — | — | 5:43 | — | — | 5:43 | — | — | 5:45 | — | — | 5:46 | — | — | 5:46 | — | — | |
6:22 | — | — | 6:20 | — | — | 6:19 | — | — | 6:17 | — | — | 6:15 | — | — | 6:15 | — | — | 6:14 | — | |
mm | 6 | 45 | 18 | 1 | — | 2 | 1 | 4 | 3 | 2 | 1 | 2 | 6 | 2 | — | 3 | — | 2 | 5 | 20 |
Temp °C | 27 | 27 | 26 | 25 | 23 | 23 | 25 | 23 | 25 | 25 | 25 | 27 | 27 | 26 | 28 | 28 | 25 | 25 | 24 | 24 |
Feels °C | 32 | 30 | 30 | 28 | 23 | 26 | 28 | 27 | 30 | 31 | 30 | 32 | 32 | 30 | 32 | 32 | 29 | 29 | 28 | 28 |
Swell 1 Height (m) Direction Period (s) | S 9 | E 19 | E 18 | SSE 8 | SSE 8 | SE 8 | SE 8 | SE 8 | SSE 8 | SSE 8 | SSE 7 | S 7 | E 14 | E 14 | ESE 9 | ESE 13 | ESE 9 | ESE 8 | ESE 8 | ESE 9 |
614 | 7 | 6 | 468 | 230 | 158 | 151 | 149 | 126 | 110 | 76 | 48 | 89 | 192 | 49 | 187 | 227 | 192 | 290 | 415 | |
Swell 2 Height (m) Direction Period (s) | ESE 10 | — | — | E 18 | ENE 7 | NE 6 | E 15 | SSW 8 | E 9 | E 14 | E 14 | E 13 | SSW 7 | SSW 7 | E 13 | S 7 | E 13 | E 13 | E 13 | E 12 |
40 | — | — | 6 | 57 | 31 | 17 | 12 | 53 | 61 | 63 | 88 | 17 | 17 | 85 | 15 | 83 | 52 | 30 | 28 | |
Swell 3 Height (m) Direction Period (s) | — | — | — | E 18 | SSW 8 | ENE 7 | E 17 | E 15 | E 16 | — | ESE 10 | ESE 10 | ESE 10 | SSE 7 | S 7 | — | S 7 | SSW 8 | SSW 8 | SSW 8 |
— | — | — | 6 | 23 | 10 | 23 | 38 | 44 | — | 18 | 19 | 31 | 9 | 15 | — | 14 | 13 | 12 | 11 | |
Wind waves Height (m) Direction Period (s) | ESE 8 | SSE 10 | S 9 | NE 2 | NE 6 | NE 6 | ENE 5 | NNE 4 | E 8 | E 7 | E 6 | E 5 | E 5 | E 5 | ESE 5 | ESE 4 | — | — | — | NE 4 |
224 | 1845 | 1108 | 1 | 130 | 111 | 19 | 3 | 57 | 38 | 21 | 25 | 31 | 34 | 17 | 17 | — | — | — | 12 | |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 0 | 50 | 9 | 0 | 0 | 9 | 9 | 9 | 0 | 0 | 9 | 9 | 9 | 0 | 9 | 20 | 0 | 0 | 0 | 0 |
Best forecast wave conditions in Shikoku | ||||||||||||||||||||
Best forecast wave conditions in Japan | ||||||||||||||||||||
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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.










