San Francisco, United States · America/Los_Angeles

Fort Point

A cobble ledge that only works in a real swell, and only with enough tide to keep it from grinding.

05:00 local · 2026-10-04

44% — the read for this hour

Marginal44%

Swell

0.56 m

Period

6 s

Swell from

289°

Wind

1.6 m/s

Wind from

114°

Air

18°C

Marginal44%

Marginal — one good hour at most. At Fort Point on this hour the read is 44%. What earns it: peel speed at 19.7 km/h. What costs it: tide window at 3.05 m over the take-off.

2 hours worth driving for today: 00:00, 01:00.

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.

Fort Point · 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: San Francisco
Datum: MLLW
Range: 1.82 m
Mean: 0.97 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 · Fort PointFringing reef — the swell stands up on a shallow shelf

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

0.85 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 44%seal 61f78103927d…

Water over take-off: exposed
Break height: 0.32 m
Peel speed: 19.7 km/h
Wave power: 1.2 kW/m

Marginal — one good hour at most. At Fort Point on this hour the read is 44%. What earns it: peel speed at 19.7 km/h. What costs it: tide window at 3.05 m over the take-off.

Every factor, re-weighted for this tide

Swell power1.2 kW/m · 1.2%
Peel speed19.7 km/h · 19.8%
Wind quality1.6 m/s straight offshore · 11.4%
Tide window3.05 m over the take-off · 0.0%
Direction match13° off the 302° peel · 12.0%
Period cleanliness5.9 s · 0.0%

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 power1.2 kW/m · 1.2%
weight 0.220
Peel speed19.7 km/h · 19.8%
weight 0.200
Wind quality1.6 m/s straight offshore · 11.4%
weight 0.200
Tide window3.05 m over the take-off · 0.0%
weight 0.180
Direction match13° off the 302° peel · 12.0%
weight 0.120
Period cleanliness5.9 s · 0.0%
weight 0.080

engine seal 61f78103927dc54a80d2fdc4a2dc82cc8949efcc3b5acb864d797214339d7746738be32fd7bea7e8d19acbf2b5f386e5

Swell power
P = 1/16 · rho · g · Hs² · Tp = 0.628 · 0.56² · 6 = 1.2 kW/m, against a 22 kW/m "serious day" reference.
Peel speed
c = sqrt(g · depth) = sqrt(9.81 · 3.05 m) = 19.7 km/h over a 3.05 m take-off, with 0.32 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 offshore at 1.6 m/s. Alignment = 1 − (1 + cos 175°)/2 = 1.00; speed envelope at 1.6 m/s = 0.57. Product 0.57.
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 289°, this break peels cleanly from 302°. 13° of error: inside 12° is full marks, past 75° the swell wraps the headland and does not arrive.
Period cleanliness
Tp = 5.9 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 20:28 UTC168 hourly rows, swell and wind wave.
liveOpen-Meteo Forecast APICC BY 4.0, non-commercial attribution requiredfetched 2026-10-04 20:28 UTC168 hourly rows, wind and air.
liveNOAA CO-OPS tide predictionsU.S. Government public domainfetched 2026-10-04 20:28 UTC144 hourly predictions, MLLW datum, station 9414290 (San Francisco).

Snapshot generated 2026-10-04T20:28:09.517Z. Break orientation, reef slope and take-off depth come from this project's catalogue and are labelled as estimates, not survey data.