Oʻahu, United States · Pacific/Honolulu

Sandy Beach

Sharp reef make-up with a close-out on a low tide and a workable shoulder on a mid.

20:00 local · 2026-10-04

50% — the read for this hour

Marginal50%

Swell

0.64 m

Period

7 s

Swell from

88°

Wind

7.6 m/s

Wind from

57°

Air

25°C

Marginal50%

Marginal — one good hour at most. At Sandy Beach on this hour the read is 50%. What earns it: peel speed at 13.1 km/h. What costs it: wind quality at 7.6 m/s 31° off.

23 hours worth driving for today: 00:00, 01:00, 02:00, 03:00, 04:00, 05:00, 06:00, 07:00, 08:00, 09:00, 10:00, 11:00, 12:00, 13:00, 14:00, 15:00, 16:00, 17:00, 18:00, 19:00, 21:00, 22:00, 23:00.

Tide window for a beachbreak: 0.8–2.2 m of water over the take-off; below 0.30 m it works across the tide matters and the reef is exposed.

Sandy Beach · 24 hours, local timelive data

score tide (dashed, MLLW) swell height now

Dashed line is the tide above MLLW, solid line is the swell height. Column height is the engine score for that hour. Faded columns are gated. The hour you select is in the URL, so this page is shareable as-is.

Tide station

Station: Honolulu, Oʻahu
Datum: MLLW
Range: 0.58 m
Mean: 0.30 m

Signature interaction

Drag the tide and watch the reef change its mind

The cross-section is drawn from the break's own reef slope. Every change re-runs the shared engine on the server and returns a fresh seal — this control cannot work without the API.

Seabed cross-section · Sandy BeachBeachbreak — sand shifting under the take-off

Drag the tide — what-if only, nothing stored is changed

0.15 m

The dashed arrow is the peel, at c = √(g·depth). More water over the take-off means a faster peel, which is why the same swell behaves differently at low and mid tide.

Re-solved by swellread-engine/2026.10.1

Marginal 50%seal 014095d2d6ea…

Water over take-off: exposed
Break height: 0.28 m
Peel speed: 13.1 km/h
Wave power: 1.8 kW/m

Marginal — one good hour at most. At Sandy Beach on this hour the read is 50%. What earns it: peel speed at 13.1 km/h. What costs it: wind quality at 7.6 m/s 31° off.

Every factor, re-weighted for this tide

Swell power1.8 kW/m · 1.8%
Peel speed13.1 km/h · 20.0%
Wind quality7.6 m/s 31° off · 1.4%
Tide window1.35 m over the take-off · 18.0%
Direction match40° off the 128° peel · 7.0%
Period cleanliness7.0 s · 1.7%

Show your working

Every factor, its weight, and the arithmetic behind it

Weights are renormalised over the factors that have real data behind them. A factor with no data is dropped and said so, never quietly scored at zero.

Swell power1.8 kW/m · 1.8%
weight 0.220
Peel speed13.1 km/h · 20.0%
weight 0.200
Wind quality7.6 m/s 31° off · 1.4%
weight 0.200
Tide window1.35 m over the take-off · 18.0%
weight 0.180
Direction match40° off the 128° peel · 7.0%
weight 0.120
Period cleanliness7.0 s · 1.7%
weight 0.080

engine seal 014095d2d6ea6816c135f48204d46a745c8ac8e1c9bc6a127e50ae189d797035f1b3cdef3f4da08ace9cec3b72630e6d

Swell power
P = 1/16 · rho · g · Hs² · Tp = 0.628 · 0.64² · 7 = 1.8 kW/m, against a 22 kW/m "serious day" reference.
Peel speed
c = sqrt(g · depth) = sqrt(9.81 · 1.35 m) = 13.1 km/h over a 1.35 m take-off, with 0.28 m standing up. Full marks 8.5–19 km/h: slower is mush, faster than ~25 km/h is unridable.
Wind quality
Wind is 31° off at 7.6 m/s. Alignment = 1 − (1 + cos 31°)/2 = 0.07; speed envelope at 7.6 m/s = 1.00. Product 0.07.
Tide window
beachbreak works across the tide. Ideal band 0.8–2.2 m of water over the take-off; below 0.30 m the reef is exposed.
Direction match
Swell from 88°, this break peels cleanly from 128°. 40° of error: inside 12° is full marks, past 75° the swell wraps the headland and does not arrive.
Period cleanliness
Tp = 7.0 s. Energy organises between 6 s and 9.5 s; beyond 14 s the swell stands up steeper than a shallow reef can hold, so the score is eased off by up to 35%.

Provenance

Every number above came from one of these

liveOpen-Meteo Marine APICC BY 4.0, non-commercial attribution requiredfetched 2026-10-04 20:27 UTC168 hourly rows, swell and wind wave.
liveOpen-Meteo Forecast APICC BY 4.0, non-commercial attribution requiredfetched 2026-10-04 20:27 UTC168 hourly rows, wind and air.
liveNOAA CO-OPS tide predictionsU.S. Government public domainfetched 2026-10-04 20:27 UTC144 hourly predictions, MLLW datum, station 1611400 (Honolulu, Oʻahu).

Snapshot generated 2026-10-04T20:27:45.385Z. Break orientation, reef slope and take-off depth come from this project's catalogue and are labelled as estimates, not survey data.