Surf Forecasts:
Monabe Rivermouth surf forecast from 10 Sep 2026:
- Best quality surf: Friday 11 Sep, 12AM (local time) - 4ft (1.2m), 7s period, SE swell with glassy winds.
- Most powerful swell: Sunday 13 Sep, 3PM (local time) - 3.5ft (1.1m), 13s period, ESE swell with 408 kJ wave energy.
- Next surfable swell (1★+): Friday 11 Sep, 12AM (local time) - 4ft (1.2m), 7s period with SE 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 (Sep 11) at 12AM. The primary swell is predicted to be 1.2m and 7s period with a secondary swell of 1.0m and 6s. The wind is predicted to be glassy as the swell arrives.
The most powerful waves expected at Monabe Rivermouth in the next 16 days are 1.1m 13s and forecast to arrive on Sunday (Sep 13) at 3PM. Winds are predicted to be onshore at the time the swell arrives. The largest open ocean swell (not directed at the beach) is 1.1m 6s period and expected on Friday (Sep 11) at 3AM.
| Wave Type | Time (JST) & Date | Wave Height & Period |
|---|---|---|
| Next good surf (1 star+) | 12AM (Fri 11th Sep) | 4ft (1.2m) 7s |
| Best Surf | 12AM (Fri 11th Sep) | 4ft (1.2m) 7s |
| Most Powerful | 3PM (Sun 13th Sep) | 3.5ft (1.1m) 13s |
Table - best surf conditions forecast for Monabe Rivermouth over the next 16 days.
The Lowdown
Alright, Rusty here, and let’s be real: it’s a slow start with next to nothing for a week. The first chance to even think about surfing is Monday the 14th, and it’s pretty weak. So, prepare for a dry spell before it gets good.
First spot to talk about is Monabe Rivermouth. This break is a rare one, doesn’t come alive often. The water temp is about 84°, which is a touch warmer than average, feels good. Starting on Monday the 14th, we see a small swell of about 3ft from the ESE, with a period of 9 seconds. Energy is low at 243, and while it’s glassy in the morning, it’s just surfable, nothing special. That small ESE swell hangs around through Tuesday, around 3ft to 5ft, with light winds. If you’re jonesing, you can get wet, but don’t expect much.
Now, here’s where it gets real. On Friday the 18th, everything changes. The morning brings a clean 5ft swell from the SE, with a long 16-second period. The energy jumps to 1562, and the wind is glassy. This is a pure groundswell, and at a rivermouth, it’ll line up nicely. This is the first real standout of the forecast. The crowd is "sometimes" a factor, but that morning glass will be worth it.
The weekend blows up, but only for the experts. Saturday the 19th brings solid 13ft surf from the SE, with the same 16-second period. It’s massive. The afternoon cleans up with glassy offshore NE winds, and the energy is pumping at 9373. Sunday the 20th is even bigger: 15ft in the morning, peaking at 16ft in the afternoon, glassy and cranking. Energy is 11738. This is heavy, expert-only stuff. Beginners, stay out.
The absolute peak, the one to mark on your calendar, is Monday the 21st. We’re looking at a massive 23ft to 25ft SSE groundswell, 16-second period. The morning is glassy with a monster energy reading of 23608. This is exceptional, big-wave territory. The wave faces will be huge. That morning is the session for the elite. The afternoon gets choppy with cross-shore wind.
After that big swell, Tuesday and Wednesday get messy with strong rain and onshore winds, ruining the quality. The swell drops fast, and by Thursday and Friday the 25th, we’re back to tiny 1ft to 2ft slop with no energy. The run is over.
So, in short: it’s a slow start, then a massive, explosive finish. The standout is the morning of Monday the 21st for the big-wave crew, and the Friday the 18th morning for a cleaner taste of that groundswell.
Rusty.
Short Range ForecastHeavy rain (total 20mm), heaviest during Thu afternoon. Warm (max 28°C on Sat afternoon, min 23°C on Thu afternoon). Wind will be generally light. | Days 5-7 Weather SummaryHeavy rain (total 40mm), heaviest during Mon night. Warm (max 28°C on Sun afternoon, min 22°C on Mon night). Wind will be generally light. | |||||||||||||||||||
Thu 10 | Friday 11 | Saturday 12 | Sunday 13 | Monday 14 | Tuesday 15 | Wednesday 16 | ||||||||||||||
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) | SSE 8 | SE 7 | SSE 7 | SSE 7 | S 7 | E 13 | E 14 | E 14 | E 13 | ESE 13 | ESE 8 | ESE 8 | ESE 9 | SE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 |
Wave Graph  | ||||||||||||||||||||
 kJ | 123 | 156 | 97 | 164 | 127 | 88 | 89 | 192 | 85 | 408 | 184 | 140 | 211 | 237 | 282 | 255 | 180 | 151 | 147 | 116 |
Wind (km/h) | ||||||||||||||||||||
Wind State on-shore cross-onshore cross-shore cross-offshore off-shore glassy | glassy | glassy | glassy | cross-on | glassy | glassy | glassy | cross-off | glassy | on | cross-off | glassy | on | on | glassy | glassy | glassy | glassy | glassy | off |
High Tide | 5:53PM1.84m | 5:36AM1.91m | 6:18PM1.86m | 6:17AM1.93m | 6:43PM1.87m | 6:55AM1.89m | 7:06PM1.85m | 7:33AM1.81m | 7:27PM1.81m | 8:10AM1.69m | 7:49PM1.75m | 8:48AM1.55m | 8:09PM1.68m | |||||||
Low Tide | 11:42PM0.58m | 12:00PM0.17m | 00:14AM0.45m | 12:32PM0.26m | 00:46AM0.35m | 1:01PM0.39m | 1:18AM0.30m | 1:29PM0.54m | 1:49AM0.31m | 1:53PM0.70m | 2:22AM0.36m | 2:16PM0.85m | 2:58AM0.44m | |||||||
 |  |  |  |  | | |  |  | |  | | | | | |  |  | |  | |
 | — | — | 5:43 | — | — | 5:45 | — | — | 5:46 | — | — | 5:46 | — | — | 5:47 | — | — | 5:48 | — | — |
 | 6:19 | — | — | 6:17 | — | — | 6:15 | — | — | 6:15 | — | — | 6:14 | — | — | 6:12 | — | — | 6:10 | — |
mm | 7 | 3 | 3 | 4 | — | 1 | 2 | — | — | — | 2 | — | 1 | 17 | 7 | 8 | — | 5 | 3 | 1 |
Temp °C | 23 | 24 | 27 | 27 | 25 | 27 | 28 | 26 | 28 | 28 | 25 | 28 | 27 | 25 | 23 | 23 | 23 | 23 | 22 | 23 |
Feels °C | 27 | 28 | 32 | 32 | 29 | 32 | 33 | 31 | 32 | 32 | 29 | 31 | 30 | 29 | 27 | 28 | 27 | 26 | 26 | 27 |
Swell 1 Height (m) Direction Period (s) | SSE 8 | SE 7 | SSE 7 | SSE 7 | S 7 | S 7 | S 7 | E 14 | ESE 9 | S 7 | ESE 8 | ESE 8 | ESE 9 | SE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 | ESE 9 |
| kJ | 123 | 156 | 97 | 164 | 127 | 61 | 34 | 192 | 47 | 8 | 184 | 140 | 211 | 237 | 282 | 255 | 180 | 151 | 147 | 116 |
Swell 2 Height (m) Direction Period (s) | E 15 | SSW 8 | E 7 | E 14 | ENE 4 | E 13 | E 14 | SSE 7 | S 7 | SSW 7 | E 13 | E 13 | E 12 | E 12 | E 14 | E 14 | E 13 | E 14 | E 13 | E 13 |
| kJ | 17 | 20 | 65 | 61 | 11 | 88 | 89 | 35 | 23 | 9 | 83 | 82 | 47 | 69 | 37 | 57 | 55 | 63 | 51 | 53 |
Swell 3 Height (m) Direction Period (s) | E 17 | ESE 11 | E 14 | — | E 14 | ENE 4 | ESE 10 | ESE 9 | E 13 | — | S 6 | S 7 | S 7 | S 7 | E 12 | S 7 | S 7 | S 7 | S 6 | S 6 |
| kJ | 23 | 22 | 33 | — | 63 | 6 | 37 | 33 | 85 | — | 7 | 4 | 4 | 4 | 11 | 1 | 1 | 1 | 1 | 1 |
Wind waves Height (m) Direction Period (s) | ENE 4 | E 6 | — | E 4 | NE 4 | — | NE 4 | — | E 4 | ESE 13 | — | — | — | — | — | — | NE 4 | NE 4 | NE 4 | ENE 4 |
| kJ | 22 | 66 | — | 28 | 14 | — | 4 | — | 3 | 408 | — | — | — | — | — | — | 3 | 5 | 4 | 7 |
Nearest Offshore or Glassy | ||||||||||||||||||||
Distance (km) | 9 | 9 | 9 | 9 | 20 | 0 | 9 | 9 | 0 | 9 | 335 | 0 | 0 | 20 | 0 | 0 | 0 | 0 | 0 | 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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