Kwajalein Atoll, Marshall Islands · Pacific/Kwajalein

Kwajalein Pass

A pass on the south-east rim of the atoll. Clean lines on a northerly, wall-to-wall on a big southerly.

03:00 local · 2026-10-05

49% — the read for this hour

Marginal49%

Swell

0.68 m

Period

11 s

Swell from

249°

Wind

9.3 m/s

Wind from

245°

Air

28°C

Marginal49%

Marginal — one good hour at most. At Kwajalein Pass on this hour the read is 49%. What earns it: peel speed at 15.3 km/h. What costs it: direction match at 177° off the 72° peel.

19 hours worth driving for today: 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, 20:00, 21:00, 22:00, 23:00.

Tide window for a reef pass: 0.9–2 m of water over the take-off; below 0.60 m it needs the pass covered matters and the reef is exposed.

Kwajalein Pass · 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: Kwajalein Atoll
Datum: MLLW
Range: 1.52 m
Mean: 0.53 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 · Kwajalein PassReef pass — a channel cut through the outer barrier reef

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

0.55 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 49%seal 3817b1858a36…

Water over take-off: exposed
Break height: 0.36 m
Peel speed: 15.3 km/h
Wave power: 3.1 kW/m

Marginal — one good hour at most. At Kwajalein Pass on this hour the read is 49%. What earns it: peel speed at 15.3 km/h. What costs it: direction match at 177° off the 72° peel.

Every factor, re-weighted for this tide

Swell power3.1 kW/m · 3.1%
Peel speed15.3 km/h · 20.0%
Wind quality9.3 m/s straight onshore · 0.0%
Tide window1.85 m over the take-off · 18.0%
Direction match177° off the 72° peel · 0.0%
Period cleanliness10.7 s · 8.0%

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 power3.1 kW/m · 3.1%
weight 0.220
Peel speed15.3 km/h · 20.0%
weight 0.200
Wind quality9.3 m/s straight onshore · 0.0%
weight 0.200
Tide window1.85 m over the take-off · 18.0%
weight 0.180
Direction match177° off the 72° peel · 0.0%
weight 0.120
Period cleanliness10.7 s · 8.0%
weight 0.080

engine seal 3817b1858a365dae67cbc80e5dc3a1ab63d607d1e03a8c6973a73b36d28aeeef5f7afb72968d8ebaefb7d30f1ac25dc7

Swell power
P = 1/16 · rho · g · Hs² · Tp = 0.628 · 0.68² · 11 = 3.1 kW/m, against a 22 kW/m "serious day" reference.
Peel speed
c = sqrt(g · depth) = sqrt(9.81 · 1.85 m) = 15.3 km/h over a 1.85 m take-off, with 0.36 m standing up. Full marks 8.5–19 km/h: slower is mush, faster than ~25 km/h is unridable.
Wind quality
Wind is straight onshore at 9.3 m/s. Alignment = 1 − (1 + cos 4°)/2 = 0.00; speed envelope at 9.3 m/s = 0.88. Product 0.00.
Tide window
reef pass needs the pass covered. Ideal band 0.9–2 m of water over the take-off; below 0.60 m the reef is exposed.
Direction match
Swell from 249°, this break peels cleanly from 72°. 177° of error: inside 12° is full marks, past 75° the swell wraps the headland and does not arrive.
Period cleanliness
Tp = 10.7 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 20:31 UTC168 hourly rows, swell and wind wave.
liveOpen-Meteo Forecast APICC BY 4.0, non-commercial attribution requiredfetched 2026-10-04 20:31 UTC168 hourly rows, wind and air.
liveNOAA CO-OPS tide predictionsU.S. Government public domainfetched 2026-10-04 20:31 UTC144 hourly predictions, MLLW datum, station 1820000 (Kwajalein Atoll).

Snapshot generated 2026-10-04T20:31:07.811Z. Break orientation, reef slope and take-off depth come from this project's catalogue and are labelled as estimates, not survey data.