Surf Forecasts:
Monabe Rivermouth surf forecast from 18 Aug 2026:
- Best quality surf: Tuesday 25 Aug, 6PM (local time) - 5.5ft (1.7m), 13s period, SE swell with cross-offshore winds.
- Most powerful swell: Tuesday 25 Aug, 9PM (local time) - 6ft (1.8m), 13s period, SE swell with 1,144 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 1.8m 13s and forecast to arrive on Tuesday (Aug 25) at 9PM. Winds are predicted to be glassy at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.2m 9s period and expected on Saturday (Aug 22) at 12AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 3AM (Fri 21st Aug) | 3.5ft (1.0m) 9s |
| Best Surf | 6PM (Tue 25th Aug) | 5.5ft (1.7m) 13s |
| Most Powerful | 9PM (Tue 25th Aug) | 6ft (1.8m) 13s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright folks, Rusty here. Let’s be real about this stretch of water. It’s a quiet start and we’re waiting a while for the good stuff to show up.
The first week is basically a write-off for any decent waves. From Tuesday the 18th right through until Sunday the 23rd, we’re looking at small, weak swell with very ordinary conditions. That’s a solid six-day gap with nothing to get excited about. The energy is barely registering and the period is short, so don’t bother paddling out.
The first real sign of life comes on Friday the 21st morning. Monabe Rivermouth (river) shows a tiny spike in energy with glassy conditions on a 3ft SSE swell, but it’s still messy. The morning of Tuesday the 25th is the first hint of something bigger on the horizon. The swell jumps to 2ft from the SE, but the period is a very long 17 seconds, and the energy is building. It’s glassy, but that long period at a river mouth can be a bit tricky – it might not wrap in perfectly.
Now, hold onto your board. The stand-out window is from the morning of Wednesday the 26th through to the morning of Saturday the 29th. This is the real deal. Wednesday morning the 26th delivers 8ft of SSE swell with clean, cross-offshore winds. Thursday morning the 27th is even better: 10ft SSE swell and clean. The absolute best of the bunch looks like Friday morning the 28th. We’re talking 12ft groundswell from the S, with a very long 16-second period, and glassy conditions. The energy is massive. This is big, powerful, and clean – for experienced surfers only. Saturday morning the 29th stays solid with 12ft S swell and glassy conditions. A true standout run.
After that, the swell drops back down. By Sunday morning the 30th it’s down to 7ft with a short period, and conditions get iffy. There’s a bit of a rebound at the start of September, with 8ft to 8ft ESE swells and clean offshore winds on Tuesday the 1st and Wednesday the 2nd. A solid second option, but not the same quality as the big late-August swell.
Rusty out.
Short Range ForecastLight rain (total 2mm), mostly falling on Tue afternoon. Warm (max 28°C on Tue afternoon, min 24°C on Tue night). Wind will be generally light. | Days 5-7 Weather SummaryMostly dry. Warm (max 29°C on Fri afternoon, min 24°C on Sat night). Wind will be generally light. | |||||||||||||||||||
Tue 18 | Wednesday 19 | Thursday 20 | Friday 21 | Saturday 22 | Sunday 23 | Monday 24 | ||||||||||||||
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 8 | ESE 8 | ESE 8 | ESE 7 | ESE 10 | S 9 | S 9 | S 9 | S 10 | ESE 11 | SE 12 | E 10 | E 10 | SE 11 | E 10 | SE 11 | E 12 | E 12 | E 12 |
Wave Graph  | ||||||||||||||||||||
 kJ | 36 | 76 | 68 | 87 | 43 | 38 | 52 | 123 | 125 | 279 | 45 | 36 | 33 | 35 | 35 | 48 | 29 | 47 | 75 | 72 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | on | cross-off | glassy | on | glassy | glassy | on | off | glassy | on | glassy | glassy | on | glassy | glassy | on | cross-off | glassy | on | glassy |
High Tide | 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 | 4:50PM1.43m | 2:38AM1.41m | 5:10PM1.53m | ||||||||
Low Tide | 3:46AM0.54m | 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 | ||||||||
 |  |  | |  | | | | | | | | | | | | | | | | |
 | — | — | 5:28 | — | — | 5:28 | — | — | 5:30 | — | — | 5:31 | — | — | 5:31 | — | — | 5:31 | — | — |
 | 6:47 | — | — | 6:46 | — | — | 6:45 | — | — | 6:45 | — | — | 6:44 | — | — | 6:42 | — | — | 6:40 | — |
mm | 1 | 1 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Temp °C | 28 | 26 | 28 | 28 | 26 | 28 | 28 | 26 | 28 | 29 | 26 | 29 | 29 | 26 | 28 | 28 | 25 | 29 | 28 | 26 |
Feels °C | 31 | 31 | 32 | 31 | 31 | 31 | 31 | 31 | 31 | 32 | 31 | 32 | 32 | 30 | 30 | 31 | 28 | 32 | 31 | 31 |
Swell 1 Height (m) Direction Period (s) | ESE 6 | ESE 8 | ESE 8 | SE 10 | ESE 7 | E 7 | S 9 | S 9 | S 9 | S 10 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 10 |
| kJ | 36 | 76 | 68 | 26 | 43 | 26 | 52 | 123 | 125 | 279 | 259 | 220 | 181 | 188 | 147 | 147 | 119 | 130 | 133 | 145 |
Swell 2 Height (m) Direction Period (s) | E 8 | SE 10 | SE 10 | SSW 8 | SE 10 | ESE 10 | ESE 7 | ESE 10 | S 11 | ESE 11 | ESE 11 | SE 12 | E 10 | E 10 | E 10 | E 10 | E 9 | E 12 | E 12 | E 12 |
| kJ | 33 | 27 | 27 | 11 | 26 | 38 | 15 | 41 | 85 | 44 | 45 | 36 | 33 | 31 | 35 | 48 | 28 | 47 | 75 | 72 |
Swell 3 Height (m) Direction Period (s) | SSW 8 | SSW 7 | SSW 8 | SW 9 | SSW 8 | SSW 8 | ESE 10 | E 7 | ESE 11 | E 7 | E 6 | E 10 | ESE 10 | ESE 13 | SE 11 | SE 11 | SE 11 | SE 10 | SE 10 | SE 9 |
| kJ | 19 | 11 | 11 | 3 | 11 | 13 | 39 | 15 | 44 | 8 | 7 | 16 | 10 | 35 | 29 | 30 | 29 | 36 | 34 | 21 |
Wind waves Height (m) Direction Period (s) | — | — | — | ESE 8 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| kJ | — | — | — | 87 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 50 | 9 | 9 | 50 | 9 | 9 | 42 | 9 | 0 | 42 | 9 | 9 | 42 | 9 | 9 | 42 | 9 | 9 | 75 | 9 |
Best forecast wave conditions in Shikoku | ||||||||||||||||||||
Best forecast wave conditions in Japan | ||||||||||||||||||||
Header Global | ||||||||||||||||||||
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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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