
Surf Forecasts:
Monabe Rivermouth surf forecast from 9 Sep 2026:
- Best quality surf: Wednesday 9 Sep, 6PM (local time) - 5ft (1.6m), 8s period, SSE swell with offshore winds.
- Most powerful swell: Sunday 13 Sep, 3PM (local time) - 3.5ft (1.0m), 13s period, ESE swell with 384 kJ wave energy.
- Next surfable swell (1★+): Wednesday 9 Sep, 6PM (local time) - 5ft (1.6m), 8s 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 Wednesday (Sep 09) at 6PM. The primary swell is predicted to be 1.6m and 8s period with a secondary swell of 0.4m and 6s. The wind is predicted to be offshore as the swell arrives.
The most powerful waves expected at Monabe Rivermouth in the next 16 days are 1.0m 13s and forecast to arrive on Sunday (Sep 13) at 3PM. Winds are predicted to be onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.2m 6s period and expected on Thursday (Sep 10) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6PM (Wed 9th Sep) | 5ft (1.6m) 8s |
| Best Surf | 6PM (Wed 9th Sep) | 5ft (1.6m) 8s |
| Most Powerful | 3PM (Sun 13th Sep) | 3.5ft (1.0m) 13s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
G’day, Rusty here. Let’s be straight with you – this stretch of coast is going to test your patience for a long while. The first week to ten days are pretty much a write-off. We’ve got a rivermouth that’s shy, inconsistent, and mostly offering ankle-biters or junky closeouts. The water’s sitting at 84°, which is a touch warmer than normal for this time of year, but that’s about the only mild surprise.
We start with nothing surfable on Wednesday the 9th – a mix of onshore junk and rain, with a 8ft south swell that’s running at 9 seconds but the wind is all over it. The energy is moderate at best (1081). The afternoon cleans up a bit, but the waves are ordinary.
Thursday the 10th and Friday the 11th are all about tiny, clean surf – around 3ft and 3ft – but it’s so weak and short-period that you’ll be scratching for anything. Saturday and Sunday the 12th and 13th drop off to a pathetic 2ft, with a long-period 13-14 second swell that’s just not wrapping in. It’s flat and frustrating.
The early part of the following week – Monday the 14th through Wednesday the 16th – sees a slight bump back to 3-4ft, but the period is only 9 seconds and the quality is still poor. There’s occasional glass, but it’s not worth paddling out for.
Thursday the 17th and Friday the 18th morning are still poor, but then Friday afternoon things start to stir. A 17-second south groundswell pushes the surf to 4ft, and the energy jumps to (797). It’s still ordinary, but you can feel something building.
Now, here’s the payoff. Saturday the 19th is the standout of the entire run. The swell gets serious – 8ft to 10ft from the SSE at 16 seconds – and the energy becomes very strong (3742 to 4746). Saturday morning is glassy, and the afternoon is clean with light north winds. This is the day. It’s a solid, experienced surfer’s wave, but it’s going to be good. The Monabe Rivermouth (this region) is going to light up.
Sunday the 20th holds the size at 10ft with that long period, and the morning has some cross-onshore chop, but the afternoon glass up with a light NNE breeze and it’s still excellent for the pros.
Monday the 21st is the biggest of the lot. Swell builds to 15ft to 16ft from the south at 17 seconds – a massive groundswell. The combined energy is off the charts (12049 to 14994). The morning is clean with a cross-offshore breeze, and this is too big for beginners. It’s expert territory, and it’s going to be a beast.
But then the wind turns on Tuesday the 22nd. A severe gale from the ESE blows through with 47-53 mph winds, and the whole thing becomes a total, blown-out mess. The swell is still huge at 16-18ft, but it’s completely unsurfable. That’s the trade-off.
Wednesday the 23rd morning is the freaky one. The forecast has 44ft of south swell with a 17-second period – that’s a monster, an absolute mountain. But even though the wind and tide are favorable, that’s just too much for this rivermouth. It’s going to be a washing machine, dangerous and scary. Not a surf day, it’s a survival day. The afternoon settles back to 16ft, but it’s onshore and messy.
After that, it’s all over. Thursday the 24th drops to 4ft and then fades to nothing. So, two standouts – Saturday the 19th and Monday morning the 21st. Saturday’s the better all-rounder for the average experienced surfer, while Monday is for the heavy chargers only. For the rest, it’s a waiting game.
Rusty out.
Short Range ForecastModerate rain (total 13mm), heaviest on Wed morning. Warm (max 27°C on Wed morning, min 22°C on Wed night). Wind will be generally light. | Days 4-6 Weather SummaryHeavy rain (total 84mm), heaviest during Mon night. Warm (max 28°C on Sun afternoon, min 23°C on Sun night). Wind will be generally light. | ||||||||||||||||||||
Wednesday 9 | Thursday 10 | Friday 11 | Saturday 12 | Sunday 13 | Monday 14 | Tuesday 15 | |||||||||||||||
AM | 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 8 | SSE 8 | SSE 8 | SSE 8 | SE 7 | SSE 9 | SSE 8 | SSE 7 | E 13 | E 14 | E 14 | E 13 | ESE 13 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 |
Wave Graph | |||||||||||||||||||||
1075 | 422 | 188 | 130 | 123 | 121 | 119 | 128 | 94 | 88 | 89 | 192 | 85 | 384 | 222 | 190 | 272 | 261 | 232 | 227 | 199 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross | off | off | glassy | glassy | glassy | glassy | on | glassy | glassy | cross-on | glassy | glassy | on | cross-off | glassy | cross-on | cross-on | cross-off | glassy | glassy |
High Tide | 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 | 8:10AM1.69m | 7:49PM1.75m | ||||||||
Low Tide | 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 | 1:53PM0.70m | 2:22AM0.36m | |||||||
5:43 | — | — | 5:43 | — | — | 5:43 | — | — | 5:45 | — | — | 5:46 | — | — | 5:46 | — | — | 5:47 | — | — | |
— | 6:20 | — | — | 6:19 | — | — | 6:17 | — | — | 6:15 | — | — | 6:15 | — | — | 6:14 | — | — | 6:12 | — | |
mm | 11 | — | — | — | — | 1 | — | 1 | — | 1 | 6 | 10 | — | 1 | — | — | 3 | 63 | 19 | 23 | — |
Temp °C | 27 | 25 | 24 | 24 | 25 | 24 | 27 | 27 | 25 | 27 | 27 | 26 | 27 | 28 | 25 | 27 | 27 | 25 | 23 | 24 | 24 |
Feels °C | 28 | 26 | 25 | 26 | 27 | 27 | 30 | 31 | 29 | 31 | 30 | 30 | 31 | 32 | 29 | 31 | 31 | 29 | 26 | 28 | 28 |
Swell 1 Height (m) Direction Period (s) | S 9 | SSE 8 | SSE 8 | SSE 8 | SSE 8 | SE 7 | SSE 9 | SSE 8 | SSE 7 | S 7 | S 7 | E 14 | ESE 9 | S 7 | ESE 9 | ESE 9 | E 12 | ESE 9 | ESE 9 | ESE 9 | ESE 9 |
1075 | 422 | 188 | 130 | 123 | 121 | 119 | 128 | 94 | 48 | 34 | 192 | 47 | 15 | 222 | 190 | 47 | 261 | 232 | 227 | 199 | |
Swell 2 Height (m) Direction Period (s) | E 18 | E 18 | ENE 6 | ENE 7 | E 15 | SSW 8 | E 8 | E 7 | E 14 | E 13 | E 14 | S 7 | E 13 | SSW 7 | E 13 | E 13 | S 7 | E 12 | E 12 | E 14 | E 13 |
6 | 6 | 51 | 56 | 17 | 12 | 61 | 35 | 63 | 88 | 89 | 33 | 85 | 17 | 83 | 52 | 4 | 47 | 27 | 57 | 53 | |
Swell 3 Height (m) Direction Period (s) | — | — | SSW 8 | S 8 | E 17 | ESE 11 | E 16 | E 14 | E 6 | SE 10 | ESE 10 | ESE 9 | S 7 | — | SSW 7 | S 7 | S 7 | S 7 | SSW 8 | SSW 8 | SSW 7 |
— | — | 23 | 5 | 23 | 22 | 44 | 61 | 12 | 24 | 38 | 32 | 15 | — | 9 | 8 | 4 | 4 | 7 | 6 | 5 | |
Wind waves Height (m) Direction Period (s) | — | NE 2 | NE 6 | NE 6 | ENE 5 | — | ENE 7 | — | E 6 | E 5 | E 5 | E 4 | ESE 4 | ESE 13 | — | — | ESE 9 | — | — | — | — |
— | 1 | 122 | 102 | 28 | — | 97 | — | 19 | 13 | 27 | 18 | 5 | 384 | — | — | 272 | — | — | — | — | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 9 | 0 | 0 | 9 | 9 | 9 | 0 | 77 | 9 | 9 | 20 | 0 | 9 | 574 | 0 | 0 | 50 | 20 | 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.










