San Francisco, United States · America/Los_Angeles
Ocean Beach
Cold, steep, and completely exposed. The wind factor dominates everything else on a typical afternoon.
16:00 local · 2026-10-04
41% — the read for this hour
Swell
0.62 m
Period
8 s
Swell from
218°
Wind
3.2 m/s
Wind from
254°
Air
21°C
Marginal — one good hour at most. At Ocean Beach on this hour the read is 41%. What earns it: peel speed at 19.6 km/h. What costs it: direction match at 74° off the 292° peel.
12 hours worth driving for today: 00:00, 01:00, 02:00, 03:00, 04:00, 05:00, 06:00, 07:00, 08:00, 10:00, 11:00, 12:00.
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.
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.
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
- Water over take-off
- exposed
- Break height
- 0.26 m
- Peel speed
- 19.6 km/h
- Wave power
- 2.0 kW/m
Marginal — one good hour at most. At Ocean Beach on this hour the read is 41%. What earns it: peel speed at 19.6 km/h. What costs it: direction match at 74° off the 292° peel.
Every factor, re-weighted for this tide
- Swell power2.0 kW/m · 2.0%
- Peel speed19.6 km/h · 19.9%
- Wind quality3.2 m/s 36° off · 1.8%
- Tide window3.01 m over the take-off · 12.5%
- Direction match74° off the 292° peel · 0.0%
- Period cleanliness8.2 s · 5.3%
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 power2.0 kW/m · 2.0%
weight 0.220
- Peel speed19.6 km/h · 19.9%
weight 0.200
- Wind quality3.2 m/s 36° off · 1.8%
weight 0.200
- Tide window3.01 m over the take-off · 12.5%
weight 0.180
- Direction match74° off the 292° peel · 0.0%
weight 0.120
- Period cleanliness8.2 s · 5.3%
weight 0.080
engine seal 0e551f50cff7b1e284db73cf1562cf846f5b3ac1dcb55659387b664b148eaf6051bdb802b0bf03aea22a3955ab78f335
Swell power
P = 1/16 · rho · g · Hs² · Tp = 0.628 · 0.62² · 8 = 2.0 kW/m, against a 22 kW/m "serious day" reference.
Peel speed
c = sqrt(g · depth) = sqrt(9.81 · 3.01 m) = 19.6 km/h over a 3.01 m take-off, with 0.26 m standing up. Full marks 8.5–19 km/h: slower is mush, faster than ~25 km/h is unridable.
Wind quality
Wind is 36° off at 3.2 m/s. Alignment = 1 − (1 + cos 36°)/2 = 0.10; speed envelope at 3.2 m/s = 0.93. Product 0.09.
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 218°, this break peels cleanly from 292°. 74° of error: inside 12° is full marks, past 75° the swell wraps the headland and does not arrive.
Period cleanliness
Tp = 8.2 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 21:13 UTC168 hourly rows, swell and wind wave.
- liveOpen-Meteo Forecast APICC BY 4.0, non-commercial attribution requiredfetched 2026-10-04 21:13 UTC168 hourly rows, wind and air.
- liveNOAA CO-OPS tide predictionsU.S. Government public domainfetched 2026-10-04 21:13 UTC144 hourly predictions, MLLW datum, station 9414290 (San Francisco).
Snapshot generated 2026-10-04T21:13:26.433Z. Break orientation, reef slope and take-off depth come from this project's catalogue and are labelled as estimates, not survey data.