Surf Forecasts:
Monabe Rivermouth surf forecast from 14 Aug 2026:
- Best quality surf: Saturday 15 Aug, 3AM (local time) - 2.5ft (0.8m), 10s period, S swell with offshore winds.
- Most powerful swell: Sunday 16 Aug, 9AM (local time) - 4ft (1.2m), 9s period, E swell with 251 kJ wave energy.
- Next surfable swell (1★+): Saturday 15 Aug, 3AM (local time) - 2.5ft (0.8m), 10s period with S 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 Saturday (Aug 15) at 3AM. The primary swell is predicted to be 0.8m and 10s period with a secondary swell of 0.7m and 10s. 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 1.2m 9s and forecast to arrive on Sunday (Aug 16) at 9AM. Winds are predicted to be cross-shore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.8m 10s period and expected on Saturday (Aug 15) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 3AM (Sat 15th Aug) | 2.5ft (0.8m) 10s |
| Best Surf | 3AM (Sat 15th Aug) | 2.5ft (0.8m) 10s |
| Most Powerful | 9AM (Sun 16th Aug) | 4ft (1.2m) 9s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
G’day, I’m Rusty. Let’s look at this stretch of coast.
First off, Monabe Rivermouth (river) is a rare-breaking spot, and this 16-day window is a long wait for anything decent. The first ten days or so are a real struggle. The swell is tiny, short period, and messy. Around the 14th and 15th of August, you’ve got a 0.7m easterly swell with combined energy at 127, and it’s just not enough. The water temp is 83°F, which is about 1°F above normal for this time of year, so it’s a touch warmer than average, but that doesn’t help the lack of surf.
Saturday the 15th has a glassy morning, but still that same little 0.7m swell. No go. The 16th bumps up to 1.2m easterly, but the period drops to 9 seconds, and there’s a risk of thunderstorms with a cross-shore wind. Not worth it. The next few days are all poor surf conditions with choppy winds.
The first real chance comes on Tuesday morning, 25th August. The swell hits 1.5m from the ESE with a 14-second period, combined energy at 794, and glassy calm wind. That’s a proper groundswell at a river mouth, so it’ll wrap in clean. Surfable, but ordinary conditions are noted. Still, with glassy conditions, it’s your first look.
The true standout is Wednesday morning, 26th August. We’re talking 1.9m of ESE swell, 13-second period, and combined energy of 1296 – that’s strong, powerful energy. Wind is calm and glassy. That’s clean, punchy surf for a river mouth. It’s the best of the whole outlook. The swell direction is close to the optimum east, so expect lined-up waves. Over 1.5m, it’s a bit big for beginners, but for intermediates and up, it’s a beauty. The spot rarely breaks, so if it’s on, it’s a special session.
After that, the swell fades. Thursday the 27th still has some 1.2m to 1.0m with glassy conditions, but energy drops to 406, and it’s ordinary. The rest of the run into the 29th is tiny and weak.
So your best bet is the 25th, but the clear standout is Wednesday morning 26th August. Rare break, rare conditions.
Rusty.
Short Range ForecastHeavy rain (total 21mm), heaviest during Sun morning. Warm (max 29°C on Mon morning, min 24°C on Fri night). Wind will be generally light. | Days 5-7 Weather SummaryLight rain (total 4mm), mostly falling on Mon afternoon. Warm (max 30°C on Wed morning, min 24°C on Mon night). Wind will be generally light. | |||||||||||||||||||
Fri 14 | Saturday 15 | Sunday 16 | Monday 17 | Tuesday 18 | Wednesday 19 | Thursday 20 | ||||||||||||||
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) | E 11 | E 10 | E 10 | E 10 | E 10 | E 9 | ESE 6 | ESE 6 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 8 | ESE 8 | ESE 8 | ESE 8 | ESE 7 | E 7 | SE 10 | SE 11 |
Wave Graph  | ||||||||||||||||||||
 kJ | 108 | 96 | 98 | 96 | 90 | 251 | 195 | 115 | 227 | 184 | 173 | 123 | 144 | 176 | 140 | 81 | 55 | 39 | 27 | 29 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | cross-off | glassy | on | cross-off | cross | cross-on | cross-off | cross-on | cross-on | cross-off | glassy | on | off | glassy | on | glassy | glassy | cross-on | glassy |
High Tide | 7:27PM1.86m | 7:10AM1.89m | 7:54PM1.84m | 7:51AM1.81m | 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 | |||||||
Low Tide | 1:16AM0.57m | 1:33PM0.19m | 1:52AM0.51m | 2:04PM0.37m | 2:28AM0.48m | 2:33PM0.56m | 3:05AM0.49m | 2:58PM0.75m | 3:46AM0.54m | 3:21PM0.92m | 4:36AM0.61m | 3:41PM1.08m | ||||||||
 |  |  |  |  | | | | | | |  | | | | | | | |  | |
 | — | — | 5:26 | — | — | 5:26 | — | — | 5:26 | — | — | 5:28 | — | — | 5:28 | — | — | 5:28 | — | — |
 | 6:52 | — | — | 6:52 | — | — | 6:51 | — | — | 6:49 | — | — | 6:47 | — | — | 6:46 | — | — | 6:45 | — |
mm | 1 | — | — | 1 | 1 | 6 | 7 | 3 | 2 | 3 | 1 | — | — | — | — | — | — | — | 4 | 1 |
Temp °C | 28 | 25 | 28 | 28 | 25 | 27 | 27 | 25 | 29 | 28 | 26 | 29 | 28 | 26 | 30 | 30 | 27 | 30 | 28 | 27 |
Feels °C | 30 | 29 | 30 | 31 | 29 | 30 | 29 | 28 | 31 | 31 | 30 | 32 | 31 | 30 | 32 | 34 | 32 | 33 | 31 | 32 |
Swell 1 Height (m) Direction Period (s) | SSW 9 | SSW 8 | SSW 10 | SSW 9 | SSW 9 | S 8 | S 9 | E 10 | S 8 | S 8 | S 8 | SSW 8 | ESE 8 | ESE 8 | ESE 8 | ESE 8 | ESE 7 | E 7 | E 7 | S 9 |
| kJ | 99 | 75 | 123 | 108 | 77 | 68 | 76 | 68 | 33 | 32 | 30 | 19 | 144 | 176 | 140 | 81 | 55 | 39 | 27 | 39 |
Swell 2 Height (m) Direction Period (s) | E 11 | E 10 | E 10 | E 10 | E 10 | SE 12 | E 10 | S 8 | SE 11 | SE 11 | SE 11 | SE 11 | SSW 8 | SSW 8 | SSW 8 | SSW 8 | SSW 9 | SE 10 | SE 10 | SE 11 |
| kJ | 108 | 96 | 98 | 96 | 90 | 22 | 96 | 50 | 30 | 30 | 19 | 30 | 20 | 12 | 12 | 12 | 15 | 25 | 26 | 29 |
Swell 3 Height (m) Direction Period (s) | SE 11 | S 11 | SE 10 | SE 8 | SE 12 | ESE 11 | SE 11 | SE 11 | — | SW 10 | — | SW 10 | SE 11 | SE 10 | SW 11 | ESE 10 | SE 10 | SSW 9 | S 8 | SE 6 |
| kJ | 19 | 38 | 17 | 10 | 23 | 23 | 33 | 43 | — | 4 | — | 4 | 18 | 16 | 5 | 10 | 25 | 26 | 22 | 6 |
Wind waves Height (m) Direction Period (s) | — | — | — | — | E 5 | E 9 | ESE 6 | ESE 6 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | — | — | — | — | — | — | — | — |
| kJ | — | — | — | — | 15 | 251 | 195 | 115 | 227 | 184 | 173 | 123 | — | — | — | — | — | — | — | — |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 42 | 9 | 9 | 75 | 9 | 20 | 230 | 0 | 20 | 20 | 9 | 9 | 50 | 9 | 9 | 20 | 9 | 9 | 335 | 9 |
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.
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