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.

23:00 local · 2026-10-04

31% — the read for this hour

Marginal31%

Swell

0.44 m

Period

13 s

Swell from

207°

Wind

3.4 m/s

Wind from

229°

Air

14°C

Marginal31%

Marginal — one good hour at most. At Fort Point on this hour the read is 31%. What earns it: peel speed at 18.5 km/h. What costs it: direction match at 95° off the 302° peel.

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

0.49 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 31%seal d51083186fa4…

Water over take-off: exposed
Break height: 0.25 m
Peel speed: 18.5 km/h
Wave power: 1.5 kW/m

Marginal — one good hour at most. At Fort Point on this hour the read is 31%. What earns it: peel speed at 18.5 km/h. What costs it: direction match at 95° off the 302° peel.

Every factor, re-weighted for this tide

Swell power1.5 kW/m · 1.5%
Peel speed18.5 km/h · 20.0%
Wind quality3.4 m/s straight onshore · 0.7%
Tide window2.69 m over the take-off · 0.3%
Direction match95° off the 302° peel · 0.0%
Period cleanliness12.6 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 power1.5 kW/m · 1.5%
weight 0.220
Peel speed18.5 km/h · 20.0%
weight 0.200
Wind quality3.4 m/s straight onshore · 0.7%
weight 0.200
Tide window2.69 m over the take-off · 0.3%
weight 0.180
Direction match95° off the 302° peel · 0.0%
weight 0.120
Period cleanliness12.6 s · 8.0%
weight 0.080

engine seal d51083186fa4587d4033960e53464ac7dbf838d317f2f821e5d3891fe2c9fe4cad21edda6b303b53d11e7232eaf1ab58

Swell power
P = 1/16 · rho · g · Hs² · Tp = 0.628 · 0.44² · 13 = 1.5 kW/m, against a 22 kW/m "serious day" reference.
Peel speed
c = sqrt(g · depth) = sqrt(9.81 · 2.69 m) = 18.5 km/h over a 2.69 m take-off, with 0.25 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 3.4 m/s. Alignment = 1 − (1 + cos 22°)/2 = 0.04; speed envelope at 3.4 m/s = 0.97. Product 0.04.
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 207°, this break peels cleanly from 302°. 95° of error: inside 12° is full marks, past 75° the swell wraps the headland and does not arrive.
Period cleanliness
Tp = 12.6 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 20:28 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.