This is a regional read for the whole Chiba & Shonan coasts of Japan — global wave model only — no public buoys nearby, so treat ranges as rougher. Mornings lean toward cross-shore winds (71% of the morning windows with data); afternoons lean toward cross-shore winds (71%). Confidence is reasonable for the first 2 days and drops to "rough estimate" after that.
Board ranges below are each board's full min→max spectrum from the Quivr catalog — the same chart the app draws — and "fits" counts how many of this week's half-day windows a board's wave and power windows overlap. Nothing here is a guess about a particular beach.
Estimates come from a global ocean wave model sampled offshore and translated into ranges. Actual size varies from beach to beach along this stretch; sheltered spots run smaller. Reads describe the whole coast, not one break — check wind and tide at your spot before paddling out. Reads are refreshed weekly on this page and several times a day in the Quivr app, which also matches each day against the boards in your own quiver. Notes on this week's data: The main swell comes from a direction this coast is largely shielded from. Size is a rough guess and likely smaller than open-ocean numbers suggest. The main swell arrives at an angle to this coast, so expect the smaller end of the range on most beaches. Most of the wave energy is local wind chop rather than swell — expect a disorganised, weak surface.
Day by day: Sep 22–28, 2026
Morning is 6am–noon, afternoon is noon–7pm local. Words come straight from the regional read; "No data" means the wave model had no hours for that window.
| Day | Morning | Afternoon | Confidence |
|---|---|---|---|
| Tue Sep 22 | Overhead · moderate push · light offshore wind | Overhead · moderate push · light cross-shore wind | Fairly confident |
| Wed Sep 23 | Knee- to chest-high · mellow, not much push · moderate cross-shore wind — some texture | Chest- to head-high · mellow, not much push · light onshore wind | Reasonable estimate |
| Thu Sep 24 | Waist- to chest-high · mellow, not much push · light onshore wind | Waist- to chest-high · mellow, not much push · light cross-shore wind | Rough estimate |
| Fri Sep 25 | Head-high · mellow, not much push · moderate cross-shore wind — some texture | Head-high · mellow, not much push · moderate cross-shore wind — some texture | Reasonable estimate |
| Sat Sep 26 | Head-high · mellow, not much push · strong cross-shore wind — some texture | Head- to overhead · moderate push · moderate cross-shore wind — some texture | Rough estimate |
| Sun Sep 27 | Head-high · mellow, not much push · light cross-shore wind | Chest- to head-high · mellow, not much push · light cross-shore wind | Rough estimate |
| Mon Sep 28 | Waist- to chest-high · mellow, not much push · light cross-shore wind | Waist- to chest-high · mellow, not much push · light wind | Trend only |
Boards that fit the Chiba & Shonan coasts of Japan this week
| Board | Fits | Wave size | Power | Skill |
|---|---|---|---|---|
| Webber Surfboards Fatburner | 14 of 14 windows | Knee-high → double-overhead+ | Moderate | Intermediate to advanced |
| TC Surfboards Retro Single Fin | 14 of 14 windows | Knee-high → overhead | Moderate | Beginner-friendly to intermediate |
| Kazuma Surfboards Kazuma Classic | 14 of 14 windows | Knee-high → double-overhead+ | Moderate | Beginner-friendly to intermediate |
| Channel Islands CI Mid | 14 of 14 windows | Waist-high → double-overhead+ | Moderate | Beginner-friendly to intermediate |
| TC Surfboards Twinnister | 14 of 14 windows | Waist-high → overhead | Moderate | Intermediate to advanced |
| Christenson Osprey | 14 of 14 windows | Waist-high → double-overhead+ | Moderate | Beginner-friendly to advanced |
| Haydenshapes Hypto Krypto Twin Pin FutureFlex | 14 of 14 windows | Waist-high → double-overhead+ | Moderate | Beginner-friendly to advanced |
The picks, in order
1. Webber Surfboards Fatburner
Webber Surfboards Fatburner runs knee-high to double-overhead+; that wave window overlaps every one of the 14 half-day windows we have data for this week. Its moderate power midpoint is firmer than the week's typical push, so it comes alive on the windows with more push. A small-wave shortboard with an intermediate to advanced skill window.
Quivr catalog read: The Webber Fatburner is perfect for intermediate to advanced surfers looking for a buoyant board that excels in small to medium-sized waves.
Category: Small-wave shortboard · Swallow tail · Catalog ability: intermediate
2. TC Surfboards Retro Single Fin
TC Surfboards Retro Single Fin runs knee-high to overhead; that wave window overlaps every one of the 14 half-day windows we have data for this week. Its moderate power midpoint is firmer than the week's typical push, so it comes alive on the windows with more push. A longboard with a beginner-friendly to intermediate skill window.
Quivr catalog read: The Retro Single Fin offers a nostalgic ride reminiscent of the 70s, perfect for stylish turns in a variety of wave conditions.
Category: Longboard · Catalog ability: intermediate
3. Kazuma Surfboards Kazuma Classic
Kazuma Surfboards Kazuma Classic runs knee-high to double-overhead+; that wave window overlaps every one of the 14 half-day windows we have data for this week. Its moderate power midpoint is firmer than the week's typical push, so it comes alive on the windows with more push. A longboard with a beginner-friendly to intermediate skill window.
Quivr catalog read: The Kazuma Classic is perfect for surfers of all skill levels, providing a smooth ride and responsive turns.
Category: Longboard · Catalog ability: beginner
4. Channel Islands CI Mid
Channel Islands CI Mid runs waist-high to double-overhead+; that wave window overlaps every one of the 14 half-day windows we have data for this week. Its moderate power midpoint is firmer than the week's typical push, so it comes alive on the windows with more push. A midlength with a beginner-friendly to intermediate skill window.
Quivr catalog read: The CI Mid is a versatile midlength board that excels in shoulder-high to nearly double overhead waves.
Category: Midlength · Catalog ability: intermediate · 4.0★ from 1 Quivr rating
5. TC Surfboards Twinnister
TC Surfboards Twinnister runs waist-high to overhead; that wave window overlaps every one of the 14 half-day windows we have data for this week. Its moderate power midpoint is firmer than the week's typical push, so it comes alive on the windows with more push. A twin fin with an intermediate to advanced skill window.
Quivr catalog read: The Twinnister is a high-performance twin fin that feels like a shortboard while offering the speed and maneuverability of a twin.
Category: Twin fin · Catalog ability: intermediate
6. Christenson Osprey
Christenson Osprey runs waist-high to double-overhead+; that wave window overlaps every one of the 14 half-day windows we have data for this week. Its moderate power midpoint is firmer than the week's typical push, so it comes alive on the windows with more push. A midlength with a beginner-friendly to advanced skill window.
Quivr catalog read: The Osprey is a versatile board that excels in a variety of surf conditions, offering speed and control.
Category: Midlength · Catalog ability: intermediate
7. Haydenshapes Hypto Krypto Twin Pin FutureFlex
Haydenshapes Hypto Krypto Twin Pin FutureFlex runs waist-high to double-overhead+; that wave window overlaps every one of the 14 half-day windows we have data for this week. Its moderate power midpoint is firmer than the week's typical push, so it comes alive on the windows with more push. A hybrid with a beginner-friendly to advanced skill window.
Quivr catalog read: The Hypto Krypto Twin Pin excels in a variety of conditions, making it suitable for surfers of all skill levels.
Category: Hybrid
Best fit by shape this week
One board per shape, chosen by how many of this week's 14 windows its wave and power windows overlap. Only shapes that overlap at least half the week are listed.
| Shape | Board | Fits | Wave size | Power |
|---|---|---|---|---|
| Shortboard | Webber Surfboards Fatburner | 14 of 14 windows | Knee-high → double-overhead+ | Moderate |
| Groveler | Webber Surfboards Fatburner | 14 of 14 windows | Knee-high → double-overhead+ | Moderate |
| Fish | Tomo Surfboards El Tomo Grande | 14 of 14 windows | Chest-high → double-overhead+ | Moderate |
| Twin fin | TC Surfboards Twinnister | 14 of 14 windows | Waist-high → overhead | Moderate |
| Midlength | Channel Islands CI Mid | 14 of 14 windows | Waist-high → double-overhead+ | Moderate |
| Longboard | TC Surfboards Retro Single Fin | 14 of 14 windows | Knee-high → overhead | Moderate |
| Step-up | Panda Surfboards Middle Age Rage | 14 of 14 windows | Waist-high → double-overhead+ | Soft |
What this week asks of a board on the Chiba & Shonan coasts of Japan
The week spreads from knee-high to overhead, so a single board with a wide wave window covers more sessions than a specialist. If you own two boards, split them: one for the smallest windows and one for the overhead ones.
Most windows read "mellow, not much push" for push. A board's power midpoint tells you where it will feel alive: mellower boards on the softer windows, firmer boards when the push is there. The table shows each board's own midpoint so the call is yours.
Already own one of these?
Add it to your quiver in Quivr and the Home tab does this matching for you — every day, against your own boards, for the coast you pick. If none of your boards overlap a window, it says so rather than forcing a pick.
Shopping instead? Open two of the picks above in Compare and read the low end of the wave-size range first — on a knee-high week that decides whether a board gets used.
Compare these picks head to head
Live Quivr comparison pages for pairs in this list — same spectra, side by side:
FAQ
How big will the surf be on the Chiba & Shonan coasts of Japan this week?
Across Sep 22–28, 2026 the regional read runs knee-high to overhead. The most size shows Tue Sep 22 morning, overhead (fairly confident); the smallest window is Thu Sep 24 afternoon, waist- to chest-high. Confidence is reasonable for the first 2 days and drops to "rough estimate" after that. Sheltered beaches along this stretch run smaller than the read.
Which surfboards fit the Chiba & Shonan coasts of Japan this week?
Fatburner, Retro Single Fin, Kazuma Classic overlap the most of this week's 14 surf windows on catalog wave-size and power spectra; the shapes that fit best are small-wave shortboard, longboard and midlength. Open any of them in Quivr to see the full range chart and compare two side by side.
Which day has the most size on the Chiba & Shonan coasts of Japan?
Tue Sep 22 morning, overhead (fairly confident). Size builds Fri and Sat and eases Wed, Thu, Sun and Mon. Mornings lean toward cross-shore winds (71% of the morning windows with data); afternoons lean toward cross-shore winds (71%).
Does this apply to my exact spot?
No single spot is named or predicted here. The read describes the Chiba & Shonan coasts of Japan as a whole — a stretch of coast facing roughly the same direction. Estimates come from a global ocean wave model sampled offshore and translated into ranges. Actual size varies from beach to beach along this stretch; sheltered spots run smaller. Reads describe the whole coast, not one break — check wind and tide at your spot before paddling out.
How often is this page updated?
Every week, with the same seven-day regional read the Quivr app shows on its Home tab. The app refreshes several times a day and also tells you which board in your own quiver fits each day.