Santa Rita, Guam · Pacific/Guam

Talofofo Bay

A shallow fringing reef that only stands up on a mid tide. This is the one where getting the tide wrong means getting skinned.

17:00 local · 2026-10-05

45% — the read for this hour

Marginal45%

Swell

1.28 m

Period

7 s

Swell from

227°

Wind

8.7 m/s

Wind from

234°

Air

29°C

Marginal45%

Marginal — one good hour at most. At Talofofo Bay on this hour the read is 45%. What earns it: peel speed at 12.9 km/h. What costs it: direction match at 95° off the 132° peel.

6 hours worth driving for today: 00:00, 01:00, 10:00, 11:00, 12:00, 13:00.

Tide window for a reef: 0.6–1.4 m of water over the take-off; below 0.40 m it wants the reef just covered matters and the reef is exposed.

Talofofo Bay · 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: Pago Bay, Guam
Datum: MLLW
Range: 0.59 m
Mean: 0.28 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 · Talofofo BayFringing reef — the swell stands up on a shallow shelf

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

0.46 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 45%seal 4d7695a3ebfa…

Water over take-off: exposed
Break height: 0.64 m
Peel speed: 12.9 km/h
Wave power: 6.8 kW/m

Marginal — one good hour at most. At Talofofo Bay on this hour the read is 45%. What earns it: peel speed at 12.9 km/h. What costs it: direction match at 95° off the 132° peel.

Every factor, re-weighted for this tide

Swell power6.8 kW/m · 6.8%
Peel speed12.9 km/h · 20.0%
Wind quality8.7 m/s straight onshore · 0.1%
Tide window1.31 m over the take-off · 18.0%
Direction match95° off the 132° peel · 0.0%
Period cleanliness6.6 s · 0.6%

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 power6.8 kW/m · 6.8%
weight 0.220
Peel speed12.9 km/h · 20.0%
weight 0.200
Wind quality8.7 m/s straight onshore · 0.1%
weight 0.200
Tide window1.31 m over the take-off · 18.0%
weight 0.180
Direction match95° off the 132° peel · 0.0%
weight 0.120
Period cleanliness6.6 s · 0.6%
weight 0.080

engine seal 4d7695a3ebfa64b1c4908e936221e89411ab2bb9f9dc20e3484648fe9572de31dc583c396de91d0f3e829e4f583f0621

Swell power
P = 1/16 · rho · g · Hs² · Tp = 0.628 · 1.28² · 7 = 6.8 kW/m, against a 22 kW/m "serious day" reference.
Peel speed
c = sqrt(g · depth) = sqrt(9.81 · 1.31 m) = 12.9 km/h over a 1.31 m take-off, with 0.64 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 8.7 m/s. Alignment = 1 − (1 + cos 7°)/2 = 0.00; speed envelope at 8.7 m/s = 0.94. Product 0.00.
Tide window
reef wants the reef just covered. Ideal band 0.6–1.4 m of water over the take-off; below 0.40 m the reef is exposed.
Direction match
Swell from 227°, this break peels cleanly from 132°. 95° of error: inside 12° is full marks, past 75° the swell wraps the headland and does not arrive.
Period cleanliness
Tp = 6.6 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 20:29 UTC168 hourly rows, swell and wind wave.
liveOpen-Meteo Forecast APICC BY 4.0, non-commercial attribution requiredfetched 2026-10-04 20:29 UTC168 hourly rows, wind and air.
liveNOAA CO-OPS tide predictionsU.S. Government public domainfetched 2026-10-04 20:29 UTC144 hourly predictions, MLLW datum, station 1631428 (Pago Bay, Guam).

Snapshot generated 2026-10-04T20:29:26.070Z. Break orientation, reef slope and take-off depth come from this project's catalogue and are labelled as estimates, not survey data.