Surf Forecasts:
Monabe Rivermouth surf forecast from 13 Aug 2026:
- Best quality surf: Saturday 15 Aug, 3AM (local time) - 2.5ft (0.8m), 10s period, S swell with cross-offshore winds.
- Most powerful swell: Sunday 16 Aug, 12PM (local time) - 4.5ft (1.4m), 10s period, ESE swell with 394 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 cross-offshore as the swell arrives.
The most powerful waves expected at Monabe Rivermouth in the next 16 days are 1.4m 10s and forecast to arrive on Sunday (Aug 16) at 12PM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 0.8m 9s period and expected on Thursday (Aug 13) at 6PM.
| 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 | 12PM (Sun 16th Aug) | 4.5ft (1.4m) 10s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright, Rusty here. Let’s talk about what’s on the menu for this stretch.
First off, the first week and a half is a total bust for Monabe Rivermouth. From Thursday the 13th all the way through Saturday the 22nd, it’s mostly poor surf. There’s some tiny swell, but it’s weak and the wind is messy. A few mornings go glassy, like Friday the 14th and Saturday the 15th, but the waves are barely a couple feet and the energy is low - the combined energy tops out around 232 (moderate wave energy) on the better moments, but the wave comment says “poor” or “surfable but very ordinary.” Not worth getting wet for.
Things start to look up in the second week. Sunday the 23rd has a clean 1.6m SE swell in the morning, glassy, with energy hitting 1059 (strong wave energy). That’s a groundswell with a period around 15 seconds, so it’ll have some shape at the river mouth, though it can be a little straight. The afternoon bumps up to 1.9m, still glassy. That’s getting a bit big for beginners.
The best call of the whole outlook is Monday the 24th. Early morning is sweet - 2.3m of SE groundswell, period a very long 15 seconds, glassy calm, and energy ripping at 2358 (very strong wave energy). The wave comment says “expect very good surf conditions.” That’s the one to aim for. Just keep in mind the afternoon gets choppy with cross-onshore wind, so hit it early.
Tuesday the 25th morning is still solid - 2.4m from the ESE, clean with a light offshore, energy at 2313. But the afternoon gets blown out again. After that, the swell fades and the wind turns onshore and nasty through the rest of the month.
Water temp is around 84°F at the start, about 2°F warmer than usual for the time of year - comfortable but nothing wild.
Remember, Monabe Rivermouth rarely breaks and is inconsistent, but the crowds are only sometimes around. So if you chase those good windows, you might have some space.
Honestly, the first 9 days are a total dud. The only two sessions that really matter are Monday 24th and Tuesday 25th mornings. After that, it’s back to ugly. Long-range looks promising but keep an eye on it.
Rusty.
Short Range ForecastModerate rain (total 13mm), heaviest on Thu morning. Warm (max 28°C on Thu afternoon, min 24°C on Thu night). Wind will be generally light. | Days 4-6 Weather SummaryModerate rain (total 12mm), heaviest on Sun morning. Warm (max 29°C on Sun afternoon, min 25°C on Sun night). Wind will be generally light. | ||||||||||||||||||||
Thursday 13 | Friday 14 | Saturday 15 | Sunday 16 | Monday 17 | Tuesday 18 | Wednesday 19 | |||||||||||||||
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) | E 10 | E 10 | E 9 | E 10 | E 11 | E 10 | S 10 | E 10 | E 10 | E 8 | E 10 | ESE 10 | E 10 | E 10 | E 10 | ESE 10 | E 10 | E 9 | SE 10 | SE 10 | SSE 9 |
Wave Graph  | |||||||||||||||||||||
 kJ | 30 | 28 | 43 | 98 | 108 | 96 | 117 | 71 | 94 | 191 | 158 | 282 | 346 | 296 | 250 | 131 | 90 | 40 | 26 | 26 | 292 |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-on | cross-off | glassy | on | cross-off | glassy | on | cross-off | cross | cross-on | cross-off | cross-on | cross-on | cross-off | glassy | on | cross-off | glassy | cross-on | cross-off |
High Tide | 6:59PM1.87m | 6:27AM1.93m | 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 | ||||||||
Low Tide | 12:23PM-0.02m | 00:40AM0.67m | 1:00PM0.06m | 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 | ||||||||
 | |  |  | |  |  | |  |  | | | | | | | |  | | | | |
 | 5:24 | — | — | 5:24 | — | — | 5:26 | — | — | 5:26 | — | — | 5:26 | — | — | 5:28 | — | — | 5:28 | — | — |
 | — | 6:53 | — | — | 6:52 | — | — | 6:52 | — | — | 6:51 | — | — | 6:49 | — | — | 6:47 | — | — | 6:46 | — |
mm | 4 | 3 | 1 | — | 1 | — | — | 2 | 2 | 2 | 3 | 1 | 1 | 4 | 1 | — | — | — | 1 | 3 | 7 |
Temp °C | 27 | 28 | 25 | 28 | 28 | 25 | 28 | 28 | 25 | 27 | 29 | 26 | 29 | 28 | 26 | 29 | 29 | 26 | 29 | 29 | 27 |
Feels °C | 29 | 30 | 28 | 30 | 30 | 29 | 31 | 31 | 28 | 30 | 30 | 29 | 30 | 30 | 29 | 32 | 32 | 30 | 33 | 32 | 32 |
Swell 1 Height (m) Direction Period (s) | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 9 | SSW 8 | S 10 | SSW 9 | SSW 9 | S 8 | E 10 | ESE 10 | E 10 | E 10 | E 10 | ESE 10 | E 10 | S 8 | SE 10 | SSE 5 | SSE 9 |
| kJ | 141 | 110 | 108 | 99 | 99 | 75 | 117 | 108 | 99 | 69 | 158 | 282 | 346 | 296 | 250 | 131 | 90 | 30 | 26 | 16 | 292 |
Swell 2 Height (m) Direction Period (s) | E 10 | E 10 | E 9 | E 10 | E 11 | E 10 | E 10 | E 10 | E 10 | E 10 | S 9 | S 8 | S 8 | S 8 | S 8 | S 8 | SSW 8 | E 9 | SSW 8 | E 4 | SSW 9 |
| kJ | 30 | 28 | 43 | 98 | 108 | 96 | 98 | 71 | 94 | 50 | 76 | 50 | 48 | 33 | 33 | 30 | 20 | 40 | 12 | 6 | 8 |
Swell 3 Height (m) Direction Period (s) | SE 12 | SE 12 | E 4 | SE 11 | SE 11 | S 11 | SE 10 | SE 8 | SSE 7 | SE 12 | SE 12 | SE 11 | SE 11 | SE 11 | SE 11 | SE 11 | SE 10 | SE 10 | E 8 | SE 10 | E 8 |
| kJ | 23 | 22 | 3 | 19 | 19 | 38 | 17 | 10 | 5 | 35 | 21 | 42 | 42 | 30 | 30 | 29 | 28 | 27 | 6 | 26 | 5 |
Wind waves Height (m) Direction Period (s) | E 4 | ESE 3 | — | — | — | — | — | — | E 5 | E 8 | ESE 6 | — | — | — | — | SSE 4 | — | SE 4 | ESE 5 | — | — |
| kJ | 3 | 4 | — | — | — | — | — | — | 15 | 191 | 71 | — | — | — | — | 7 | — | 10 | 20 | — | — |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 20 | 75 | 9 | 9 | 42 | 9 | 0 | 75 | 9 | 230 | 230 | 0 | 20 | 531 | 0 | 9 | 638 | 9 | 9 | 952 | 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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