Surf Forecasts:
Monabe Rivermouth surf forecast from 28 Aug 2026:
- Best quality surf: Thursday 3 Sep, 12AM (local time) - 8ft (2.4m), 11s period, SE swell with cross-offshore winds.
- Most powerful swell: Thursday 3 Sep, 6PM (local time) - 13ft (4.0m), 11s period, SSE swell with 3,663 kJ wave energy.
- Next surfable swell (1★+): Tuesday 1 Sep, 6AM (local time) - 3ft (0.9m), 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 Tuesday (Sep 01) at 6AM. The primary swell is predicted to be 0.9m and 9s period with a secondary swell of 0.5m and 14s. Another secondary swell of 0.1m and 6s is also forecast. 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 4.0m 11s and forecast to arrive on Thursday (Sep 03) at 6PM. Winds are predicted to be cross-onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.4m 11s period and expected on Friday (Sep 04) at 3PM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 6AM (Tue 1st Sep) | 3ft (0.9m) 9s |
| Best Surf | 12AM (Thu 3rd Sep) | 8ft (2.4m) 11s |
| Most Powerful | 6PM (Thu 3rd Sep) | 13ft (4.0m) 11s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
G’day, I’m Rusty.
Well, it’s a bit of a slow start around here. The next few days are pretty flat with small, weak swells and poor conditions. There’s nothing worth paddling out for until Tuesday the 1st of September, but even then it’s only marginal. We’ve got a solid run of bigger energy coming through later, but you’ll need to pick your windows carefully.
Let’s start with Monabe Rivermouth, this is the only spot on the radar. Saturday the 29th and Sunday the 30th of August are tiny – like 1ft to 1ft of easterly swell with weak energy, and the wind is cross-on or glassy but the surf is just too small. Monday is more of the same.
The first real pulse shows up Tuesday morning the 1st of September – a 3ft southerly groundswell at 9 seconds, energy jumps to moderate, and it’s glassy early. The comment says “surfable waves but very ordinary conditions,” so it’s not a standout. By Tuesday afternoon the wind swings cross-on and it gets choppy.
Wednesday the 2nd brings a bit more size (5ft) but the wind is messy and cross-on, and energy is up but the quality is poor.
The first genuine highlight comes on Thursday the 3rd of September, early morning. We’ve got a 8ft south-southeast swell, period 11 seconds – that’s a decent groundswell. Combined wave energy is strong, and it’s glassy with offshore wind from the east-southeast. The comment says “expect good surf conditions.” This is solid for experienced surfers but at 8ft it’s getting too big for beginners. The swell direction (SSE) isn’t perfect for this east-facing rivermouth, but clean glassy conditions will help. It’s a short window – by afternoon it’s 10ft with a moderate cross-onshore breeze and choppy.
Then there’s a lull through Friday and Saturday with dropping size and poor winds.
Now, the big one – Sunday the 6th of September morning. We’re talking 13ft of easterly swell, period 10 seconds, and combined wave energy is very strong. The wind is light cross-offshore from the east-northeast, and it’s clean. The comment says “expect very good surf conditions.” This is for experienced surfers only – 13ft is heavy. The optimum swell direction for this break is east, and that’s exactly what we’ve got. This is the standout session of the forecast for experts. Crowds are listed as “sometimes,” so you might have company but it won’t be packed.
The next morning, Monday the 7th of September, tops it. 21ft of east-southeast swell at 12 seconds – very long period groundswell. Combined energy is massive. Glassy with light northeast wind. The comment says “excellent surf conditions for experienced surfers.” This is huge, straight-up serious. At a rivermouth, that long-period energy will line up nicely, but it’s going to be heavy and intimidating. Only for proper experienced surfers. The afternoon drops to 15ft but gets a light cross-onshore.
Tuesday the 8th still has 12ft to 10ft of southeast groundswell. Tuesday afternoon is glassy and calls it “expect very good surf conditions.” Good clean waves for experienced crew.
Wednesday the 9th morning is also glassy with 10ft, 11-second period, and saying “expect very good surf conditions.” That’s another nice window before the wind turns cross-on later.
The second week fades a bit. Thursday the 10th has 6ft glassy but only “surfable but ordinary.” By Friday the 11th it’s back to poor and small. But then Sunday the 13th of September delivers again – 16ft east-southeast swell, period 12 seconds, energy massive, glassy calm. It says “excellent surf conditions for experienced surfers.” That’s a big, clean groundswell for the experts. Afternoon has the same 16ft but onshore wind, so morning is the go.
Water temperature at this break is 86°F, which is a touch warmer than normal for this time of year – that’s nice.
Overall, the standout is Sunday morning the 6th of September for experienced surfers – 13ft easterly swell, clean cross-offshore wind, and the right direction. Monday the 7th morning is even bigger at 21ft but that’s for the brave. For anyone else, the glassy windows on the 3rd and 9th of September mornings offer good, manageable waves.
Stay safe out there.
Rusty
Short Range ForecastModerate rain (total 10mm), heaviest on Sun night. Warm (max 30°C on Sun morning, min 24°C on Mon night). Wind will be generally light. | Days 4-6 Weather SummaryHeavy rain (total 89mm), heaviest during Thu night. Warm (max 29°C on Tue morning, min 25°C on Tue night). Winds increasing (calm on Tue morning, fresh winds from the S by Thu night). | ||||||||||||||||||||
Saturday 29 | Sunday 30 | Monday 31 | Tuesday 1 | Wednesday 2 | Thursday 3 | Friday 4 | |||||||||||||||
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 12 | E 12 | E 11 | E 11 | E 11 | S 7 | E 11 | SE 10 | S 8 | S 9 | S 8 | SSE 8 | SSE 9 | S 9 | SE 11 | SSE 11 | S 11 | S 10 | SSE 9 | SE 9 | SE 8 |
Wave Graph | |||||||||||||||||||||
44 | 44 | 36 | 22 | 21 | 51 | 21 | 24 | 68 | 152 | 169 | 252 | 318 | 270 | 1274 | 1675 | 2293 | 3650 | 1121 | 594 | 239 | |
Wind (km/h) | |||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | cross-on | cross-on | glassy | glassy | cross-on | glassy | on | on | cross-off | glassy | cross-on | cross-off | cross-on | cross-on | cross-off | glassy | cross-on | cross-on | on | cross-on | glassy |
High Tide | 6:56PM1.84m | 6:50AM1.86m | 7:19PM1.85m | 7:27AM1.82m | 7:43PM1.84m | 8:08AM1.74m | 8:08PM1.81m | 8:53AM1.62m | 8:36PM1.75m | 9:49AM1.48m | 9:09PM1.67m | 11:15AM1.35m | 9:51PM1.57m | ||||||||
Low Tide | 12:37PM0.21m | 00:51AM0.50m | 1:05PM0.28m | 1:22AM0.42m | 1:34PM0.40m | 1:56AM0.37m | 2:03PM0.55m | 2:34AM0.36m | 2:35PM0.72m | 3:19AM0.39m | 3:09PM0.91m | 4:17AM0.45m | 3:53PM1.10m | ||||||||
5:35 | — | — | 5:35 | — | — | 5:37 | — | — | 5:37 | — | — | 5:37 | — | — | 5:39 | — | — | 5:39 | — | — | |
— | 6:35 | — | — | 6:34 | — | — | 6:31 | — | — | 6:30 | — | — | 6:30 | — | — | 6:28 | — | — | 6:27 | — | |
mm | — | 3 | — | — | 1 | 5 | 1 | — | — | 1 | 3 | 2 | 3 | 7 | 4 | 1 | 3 | 65 | 14 | 5 | 11 |
Temp °C | 29 | 29 | 27 | 30 | 29 | 27 | 29 | 29 | 26 | 29 | 28 | 26 | 28 | 28 | 26 | 29 | 29 | 27 | 27 | 27 | 27 |
Feels °C | 33 | 33 | 33 | 34 | 33 | 33 | 33 | 32 | 31 | 33 | 31 | 30 | 31 | 30 | 30 | 31 | 31 | 29 | 32 | 31 | 33 |
Swell 1 Height (m) Direction Period (s) | E 12 | E 12 | E 11 | SSW 7 | SSW 7 | S 7 | SSW 8 | SSW 9 | S 8 | S 9 | S 8 | SSE 8 | SSE 9 | S 9 | SSW 12 | E 16 | S 11 | S 10 | SSE 9 | SE 9 | SE 8 |
44 | 44 | 36 | 91 | 73 | 51 | 96 | 99 | 68 | 152 | 169 | 252 | 318 | 270 | 218 | 5 | 2293 | 3140 | 1121 | 594 | 239 | |
Swell 2 Height (m) Direction Period (s) | SE 10 | SSE 9 | SE 11 | SE 10 | SE 10 | SE 10 | SE 10 | SE 10 | SW 9 | E 13 | E 13 | E 12 | E 11 | SSW 12 | SE 11 | E 16 | — | SSE 13 | SSW 10 | SSW 11 | SSW 10 |
14 | 8 | 19 | 17 | 17 | 27 | 16 | 24 | 20 | 90 | 115 | 137 | 116 | 57 | 18 | 5 | — | 18 | 229 | 460 | 331 | |
Swell 3 Height (m) Direction Period (s) | SE 13 | SSE 11 | SE 9 | E 11 | E 11 | E 11 | E 11 | E 11 | ESE 14 | SE 9 | SE 9 | SE 10 | SE 10 | SE 11 | E 18 | — | — | E 12 | E 11 | E 11 | ENE 5 |
27 | 12 | 3 | 22 | 21 | 21 | 21 | 20 | 40 | 14 | 14 | 15 | 17 | 18 | 6 | — | — | 12 | 22 | 22 | 34 | |
Wind waves Height (m) Direction Period (s) | SSW 8 | SSW 7 | SSW 8 | WSW 4 | — | — | — | — | — | E 6 | — | — | E 4 | ESE 6 | SE 11 | SSE 11 | ESE 7 | S 10 | — | — | NE 5 |
128 | 125 | 128 | 13 | — | — | — | — | — | 1 | — | — | 17 | 122 | 1274 | 1675 | 374 | 3650 | — | — | 71 | |
Nearest Offshore or Glassy | |||||||||||||||||||||
Distance (km) | 9 | 42 | 9 | 9 | 42 | 9 | 9 | 42 | 9 | 0 | 20 | 0 | 20 | 20 | 0 | 0 | 20 | 425 | 50 | 42 | 0 |
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.











