Surf Forecasts:
Monabe Rivermouth surf forecast from 19 Aug 2026:
- Best quality surf: Tuesday 25 Aug, 9PM (local time) - 10ft (3.0m), 16s period, SSE swell with cross-offshore winds.
- Most powerful swell: Wednesday 26 Aug, 9AM (local time) - 15ft (4.5m), 17s period, SSE swell with 11,249 kJ wave energy.
- Next surfable swell (1★+): Friday 21 Aug, 3AM (local time) - 3.5ft (1.0m), 9s 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 Friday (Aug 21) at 3AM. The primary swell is predicted to be 1.0m and 9s period with a secondary swell of 0.4m and 11s. 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 4.5m 17s and forecast to arrive on Wednesday (Aug 26) at 9AM. Winds are predicted to be cross-offshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.2m 5s period and expected on Wednesday (Aug 26) at 9AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 3AM (Fri 21st Aug) | 3.5ft (1.0m) 9s |
| Best Surf | 9PM (Tue 25th Aug) | 10ft (3.0m) 16s |
| Most Powerful | 9AM (Wed 26th Aug) | 15ft (4.5m) 17s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright, this is Rusty, and here's the lowdown on the local surf.
The first few days are a total bust. We've got a really sheltered river mouth spot, and it's just not doing anything. The water temp is a warm 82°, which is standard for this time of year.
From Wednesday the 19th all the way to Sunday the 23rd, the swell is flat and the conditions are trash. Don't even bother paddling out. It stays quiet through the next Monday and Tuesday, too.
Then, finally, on Tuesday the 25th, we get a proper window. The morning at Monabe Rivermouth is your best bet. We're looking at a clean 8ft groundswell from the SE with a very long 15 second period, and the wind is completely glassy. The combined wave energy is a strong 2595. The afternoon is just as clean with an 8ft swell. This is the one to wait for, but remember, this spot rarely breaks, so when it's good, it's special.
The big stuff hits mid-week. On Wednesday the 26th, we're talking a massive 15ft swell from the SSE with a 17 second period. The energy is off the charts at 11333. This is strictly for experts. The wind is a clean cross-off, so it'll be organized, but the size is intimidating. Thursday the 27th is also a big day with 15ft, but the wind gets messy.
After that huge pulse, the surf gets a bit inconsistent through the end of August and into September. There are a few glassy mornings with 7ft and 12ft swells, but the wind and tide often mess things up. The second week of the forecast is a real mixed bag – some promising swells, but the conditions are less reliable.
For my money, Tuesday the 25th is the clear winner. That's the cleanest, most powerful, and most reliable day we've got. The rest of the run is either too small, too choppy, or too big for a normal session.
Rusty.
Short Range ForecastMostly dry. Warm (max 29°C on Sat morning, min 24°C on Wed night). Wind will be generally light. | Days 5-7 Weather SummaryMostly dry. Warm (max 29°C on Sat afternoon, min 25°C on Sat night). Wind will be generally light. | |||||||||||||||||||
Wed 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | Tuesday 25 | ||||||||||||||
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 8 | ESE 7 | ESE 10 | S 8 | S 9 | S 9 | S 9 | SE 11 | SE 12 | ESE 10 | ESE 13 | ESE 13 | SE 11 | SE 12 | SE 16 | SE 14 | SE 16 | SE 15 | SE 15 | SSE 16 |
Wave Graph  | ||||||||||||||||||||
 kJ | 63 | 43 | 38 | 51 | 126 | 168 | 171 | 30 | 36 | 35 | 60 | 66 | 31 | 73 | 498 | 528 | 767 | 2551 | 3199 | 5454 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | cross-off | glassy | on | off | glassy | on | glassy | glassy | on | glassy | cross-on | on | glassy | glassy | on | glassy | glassy | glassy | cross-off |
High Tide | 9:29PM1.59m | 11:21AM1.24m | 9:56PM1.50m | 2:33PM1.21m | 10:41PM1.41m | 4:35PM1.33m | 00:46AM1.36m | 4:50PM1.43m | 2:38AM1.41m | 5:10PM1.53m | 3:40AM1.52m | 5:30PM1.61m | ||||||||
Low Tide | 3:21PM0.92m | 4:36AM0.61m | 3:41PM1.08m | 5:50AM0.67m | 3:45PM1.21m | 7:39AM0.66m | 8:21PM1.28m | 9:06AM0.57m | 9:54PM1.19m | 9:59AM0.46m | 10:30PM1.08m | 10:37AM0.35m | 10:58PM0.96m | |||||||
 |  | | | |  | | | | | | | | | | |  | | |  | |
 | — | — | 5:28 | — | — | 5:30 | — | — | 5:31 | — | — | 5:31 | — | — | 5:31 | — | — | 5:33 | — | — |
 | 6:46 | — | — | 6:45 | — | — | 6:45 | — | — | 6:44 | — | — | 6:42 | — | — | 6:40 | — | — | 6:39 | — |
mm | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 |
Temp °C | 28 | 26 | 28 | 28 | 26 | 28 | 28 | 26 | 29 | 29 | 26 | 28 | 29 | 26 | 29 | 28 | 26 | 29 | 29 | 26 |
Feels °C | 32 | 31 | 31 | 31 | 31 | 31 | 32 | 31 | 33 | 32 | 30 | 32 | 33 | 31 | 32 | 31 | 31 | 32 | 34 | 30 |
Swell 1 Height (m) Direction Period (s) | ESE 8 | ESE 7 | E 7 | S 8 | S 9 | S 9 | S 9 | S 9 | SSW 9 | SSW 9 | SSW 9 | SSW 10 | SSW 10 | SSW 9 | SSW 12 | SE 14 | SE 16 | SE 15 | SE 15 | SSE 16 |
| kJ | 63 | 43 | 26 | 51 | 126 | 168 | 171 | 169 | 177 | 173 | 188 | 218 | 218 | 136 | 256 | 528 | 767 | 2551 | 3199 | 5454 |
Swell 2 Height (m) Direction Period (s) | SE 10 | SE 10 | ESE 10 | ESE 7 | ESE 10 | ESE 11 | ESE 11 | SE 11 | SE 12 | ESE 10 | ESE 13 | E 10 | E 10 | SE 12 | SE 16 | SSW 11 | SE 13 | SSW 10 | SSW 9 | E 14 |
| kJ | 26 | 25 | 38 | 15 | 39 | 45 | 44 | 30 | 36 | 35 | 60 | 32 | 31 | 73 | 498 | 218 | 431 | 100 | 49 | 132 |
Swell 3 Height (m) Direction Period (s) | SSW 8 | SSW 8 | SSW 8 | ESE 10 | ESE 7 | ESE 7 | ESE 7 | SSW 11 | E 10 | ESE 10 | E 10 | ESE 13 | SE 11 | E 9 | E 12 | SE 17 | SSW 10 | E 12 | E 14 | SSW 9 |
| kJ | 11 | 11 | 13 | 39 | 10 | 9 | 9 | 23 | 16 | 10 | 30 | 66 | 30 | 27 | 73 | 224 | 140 | 44 | 66 | 32 |
Wind waves Height (m) Direction Period (s) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| kJ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 50 | 9 | 9 | 42 | 9 | 0 | 42 | 9 | 9 | 42 | 9 | 9 | 42 | 9 | 0 | 50 | 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.
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