Forecast vs reality
At Ocean Beach our surf-zone wave heights run about 4% high against a full-physics model; on a reef, about 16% low.
That is our model checked against a better model, not yet against the ocean. Both were given the same seafloor and the same swell. Three captured days, two California spots.
The three cases
Height · where it breaks- Ocean Beach, high tideJan 16, 2026 swell · 3.9 ft at 13 s+4.5%26 ft inshore
- Ocean Beach, low tideSame day's swell, 6 ft lower tide+3.4%157 ft inshore
- Bean Hollow, reefCaptured Aug 21, 2026 · 7.4 ft at 14 s−15.5%20 ft offshore
Ocean Beach · Jan 16, 2026 · high tide
Wave height, ft| Water depth (ft) | Surfsolver (ft) | Celeris (ft) |
|---|---|---|
| 31.2 | 3.9 | 3.9 |
| 30.5 | 3.9 | 3.9 |
| 29.6 | 4.0 | 3.8 |
| 28.6 | 4.0 | 3.8 |
| 27.7 | 4.0 | 3.8 |
| 26.5 | 4.1 | 3.7 |
| 25.2 | 4.1 | 3.7 |
| 23.9 | 4.1 | 3.9 |
| 22.9 | 4.2 | 3.9 |
| 22.0 | 4.2 | 3.8 |
| 20.9 | 4.2 | 3.8 |
| 19.8 | 4.3 | 3.8 |
| 19.4 | 4.3 | 3.9 |
| 18.8 | 4.4 | 4.0 |
| 17.6 | 4.4 | 4.0 |
| 16.8 | 4.5 | 4.0 |
| 16.4 | 4.5 | 4.0 |
| 15.8 | 4.6 | 3.9 |
| 15.3 | 4.6 | 4.2 |
| 14.4 | 4.7 | 4.4 |
| 13.1 | 4.8 | 4.5 |
| 11.5 | 4.9 | 4.3 |
| 9.7 | 5.0 | 4.6 |
| 8.7 | 5.0 | 4.5 |
| 8.2 | 4.8 | 4.4 |
| 7.9 | 4.6 | 4.2 |
| 7.2 | 4.3 | 4.1 |
| 6.8 | 3.9 | 3.7 |
| 6.0 | 3.4 | 3.4 |
| 5.5 | 3.1 | 3.0 |
| 5.3 | 2.9 | 2.9 |
| 4.9 | 2.8 | 2.7 |
| 3.6 | 2.3 | 2.8 |
| 3.2 | 1.9 | 3.0 |
| 2.5 | 1.8 | 2.6 |
| 1.4 | 0.9 | 1.7 |
Significant wave height (the average of the highest third of waves), not the surf size on a spot page. Both models start from the same 3.9 ft at the left edge. On the reef ours runs low even in deep water; that gap is still open.
Not measured yet
- Height at the break, against the oceanWe have no buoy or camera reading inside the surf zone at any of our spots.Not yet
- Whether it was any goodOnly surfers can say. Reports are open below; none published yet.Not yet
- East Coast and Australia59 breaks with no satellite or model check.Not yet
- Days 8 to 16The far range has not been scored.Not yet
- 125 of 169 breakshave never had a satellite check.Not yet
Also checked
Swell direction, by satellite47 clear passes · 44 California breaks33 pass · 14 unclear · 0 fail
On each cloud-free Sentinel-2 pass we read the swell’s crest direction out of the image and compare it with the direction our forecast gives near the break. 33 of 47 passed. 14 were too weak to call: foam, ship wakes or haze spoiled the satellite reading. None failed. Passes run Aug 2025 to Jul 2026.
It checks the table that bends swell around points and into bays. It does not check height or where the wave breaks, and it has not yet scored the solver that draws the map.
The swell we start fromCDIP's forecast vs CDIP's buoys · 4 sites10.7–12.5% median, runs low
California’s swell comes from CDIP’s MOP model before our solver touches it. Matched hour by hour against CDIP’s own buoys (22,827 hours), its median height error is 10.7–12.5% at the exposed sites and 24.4% in southern Monterey Bay, a site known for low skill. At every site it runs low, by 0.2 to 1 ft. These are short-lead comparisons; error a week out is larger. The East Coast and Australia start from NOAA GFS-Wave, which we have not compared with buoys.
The satellite method itselfAn instrument check, not a forecast checkWithin 3° of a buoy
Off Santa Cruz the satellite reading recovered the offshore swell direction to within 3° of NOAA buoy 46026. That checks the tool we measure the forecast with, which had to come first.
How we check
No single method covers a forecast. Each grounds a different part of it, and each has something it cannot see.
A full-physics modelCeleris, on the same seafloor and swell
- Grounds
- What the seafloor does to the swell in the surf zone.
- Cannot see
- The real ocean. It shares our seafloor and our swell, so it shares their errors.
SatelliteSentinel-2, crest direction by 2-D FFT
- Grounds
- Approach angle, and refraction around a point.
- Cannot see
- Height, and whether it was any good.
BuoysCDIP and NOAA, offshore
- Grounds
- The swell arriving: height, period, direction.
- Cannot see
- Everything between the buoy and the beach.
SurfersReports from people who were in the water
- Grounds
- Whether it was worth paddling out.
- Cannot see
- Nothing, and that's the point.
Tell us what it actually did
If you surfed one of our spots, this is the most useful thing you can send, especially if we got it wrong. It takes a sentence.