How accurate is TrueSwell — spot by spot

Every forecast we publish is filed, then graded hours later against the nearest NOAA buoy. Below is what the first full audit found at each break, and the correction each one now carries because of it. This page exists because no forecast should ask you to take its word for it.

2,564,505forecast / buoy pairs graded in the audit

78buoy-mapped spots audited

58 / 78spots with a consistent, correctable bias

−31%fleet error after calibration (0–48 h RMSE 1.23 → 0.85 ft)

5,212,790pairs graded since the calibrated model went live · day-1 bias now -0.62 ft

How to read the table. Bias is how far our offshore wave height sat from the buoy on average (negative = we read low). It was nearly identical at every lead time — the signature of a constant offset, which is exactly what a per-spot correction removes. Error is the typical size of a miss for forecasts 0–48 hours out, before and after removing that bias. Two spots are review — their model grid point sits in sheltered water while the reference buoy is fully exposed, so part of the gap is location, not model error; they keep the uncorrected model until we've checked them against cams.

Alaska

Spot	Buoy	Bias vs buoy	Correction	Error before	After	Cut
Yakutat (Cannon Beach)Alaska	46083	-0.57 ft	+0.57 ft	1.06 ft	0.89 ft	−16%

East Coast

Spot	Buoy	Bias vs buoy	Correction	Error before	After	Cut
Cocoa Beach PierFlorida	41113	-0.49 ft	+0.49 ft	0.60 ft	0.35 ft	−41%
Jacksonville BeachFlorida	41112	-0.55 ft	+0.55 ft	0.77 ft	0.55 ft	−30%
New Smyrna InletFlorida	41113	-0.05 ft	+0.05 ft	0.42 ft	0.42 ft	−1%
St. Augustine (A Street)Florida	41117	-0.87 ft	+0.87 ft	1.03 ft	0.55 ft	−46%
Tybee IslandGeorgia	41008	-0.69 ft	+0.69 ft	1.01 ft	0.73 ft	−27%
Higgins BeachMaine	44007	-0.09 ft	+0.09 ft	0.82 ft	0.82 ft	−1%
NahantMassachusetts	44013	-0.65 ft	+0.65 ft	0.92 ft	0.65 ft	−29%
Nantasket BeachMassachusetts	44013	-0.78 ft	+0.78 ft	1.03 ft	0.67 ft	−35%
The Wall (Hampton)New Hampshire	44098	-0.84 ft	+0.84 ft	1.12 ft	0.75 ft	−33%
Atlantic CityNew Jersey	44091	-0.71 ft	+0.71 ft	1.25 ft	1.03 ft	−18%
BelmarNew Jersey	44091	-0.92 ft	+0.92 ft	1.40 ft	1.06 ft	−25%
LBI Ship BottomNew Jersey	44091	-1.09 ft	+1.09 ft	1.51 ft	1.04 ft	−31%
Manasquan InletNew Jersey	44091	-0.87 ft	+0.87 ft	1.37 ft	1.05 ft	−23%
Lido BeachNew York	44025	-0.59 ft	+0.59 ft	1.27 ft	1.13 ft	−11%
Long BeachNew York	44025	-0.59 ft	+0.59 ft	1.27 ft	1.13 ft	−11%
Rockaway BeachNew York	44065	-0.52 ft	+0.52 ft	1.06 ft	0.92 ft	−13%
Avon PierNorth Carolina	41025	-1.26 ft	+1.26 ft	1.65 ft	1.07 ft	−35%
Cape Hatteras (Lighthouse)North Carolina	41025	-0.29 ft	+0.29 ft	1.06 ft	1.02 ft	−4%
Carolina BeachNorth Carolina	41110	-0.45 ft	+0.45 ft	0.79 ft	0.65 ft	−18%
Hatteras (Village)North Carolina	41025	-0.64 ft	+0.64 ft	1.19 ft	1.00 ft	−16%
Jennette's PierNorth Carolina	44095	-1.59 ft	+1.59 ft	1.74 ft	0.72 ft	−59%
Kitty HawkNorth Carolina	44100	-1.23 ft	+1.23 ft	1.37 ft	0.61 ft	−55%
Kure BeachNorth Carolina	41110	-0.15 ft	+0.15 ft	0.70 ft	0.68 ft	−2%
Masonboro IslandNorth Carolina	41110	-0.95 ft	+0.95 ft	1.15 ft	0.66 ft	−43%
Nags Head PierNorth Carolina	44095	-1.41 ft	+1.41 ft	1.59 ft	0.75 ft	−53%
North Topsail Beach (Seaview Pier)North Carolina	41110	-0.24 ft	+0.24 ft	0.71 ft	0.67 ft	−6%
Ocean Isle BeachNorth Carolina	41013	-0.71 ft	+0.71 ft	1.15 ft	0.90 ft	−22%
Ocracoke IslandNorth Carolina	41025	-0.99 ft	+0.99 ft	1.42 ft	1.02 ft	−28%
RodantheNorth Carolina	44095	-0.99 ft	+0.99 ft	1.19 ft	0.67 ft	−44%
Sunset BeachNorth Carolina	41013	-0.83 ft	+0.83 ft	1.22 ft	0.89 ft	−27%
Surf City (Topsail Island)North Carolina	41110	-0.36 ft	+0.36 ft	0.75 ft	0.66 ft	−12%
Topsail BeachNorth Carolina	41110	-0.39 ft	+0.39 ft	0.76 ft	0.65 ft	−14%
WavesNorth Carolina	44095	-0.83 ft	+0.83 ft	1.06 ft	0.67 ft	−37%
Wrightsville Beach (Crystal Pier)North Carolina	41110	-0.95 ft	+0.95 ft	1.15 ft	0.66 ft	−43%
Wrightsville Beach (Mercers Pier)North Carolina	41110	-0.95 ft	+0.95 ft	1.15 ft	0.66 ft	−43%
MatunuckRhode Island	44097	-0.63 ft	+0.63 ft	1.32 ft	1.15 ft	−12%
Narragansett Town BeachRhode Island	44097	-0.56 ft	+0.56 ft	1.30 ft	1.17 ft	−10%
Ruggles (Newport)Rhode Island	44097	-0.63 ft	+0.63 ft	1.33 ft	1.17 ft	−12%
Folly Beach (Washout)South Carolina	41004	-1.18 ft	+1.18 ft	1.46 ft	0.85 ft	−41%
Isle of PalmsSouth Carolina	41004	-1.17 ft	+1.17 ft	1.46 ft	0.87 ft	−40%
Myrtle BeachSouth Carolina	41013	-1.32 ft	+1.32 ft	1.61 ft	0.91 ft	−43%
Pawleys IslandSouth Carolina	41013	-1.64 ft	+1.64 ft	1.90 ft	0.96 ft	−50%
SandbridgeVirginia	44099	-1.22 ft	+1.22 ft	1.38 ft	0.66 ft	−53%
Virginia Beach (1st St Jetty)Virginia	44099	-1.22 ft	+1.22 ft	1.38 ft	0.66 ft	−53%

Gulf Coast

Spot	Buoy	Bias vs buoy	Correction	Error before	After	Cut
Gulf ShoresAlabama	42012	-0.61 ft	+0.61 ft	1.59 ft	1.47 ft	−8%
Panama City BeachFlorida	42039	-1.00 ft	+1.00 ft	1.93 ft	1.65 ft	−14%
Pensacola BeachFlorida	42012	-0.55 ft	+0.55 ft	1.42 ft	1.31 ft	−8%
Galveston (61st St Pier)Texas	42035	-0.61 ft	+0.61 ft	0.85 ft	0.59 ft	−31%

Hawaii

Spot	Buoy	Bias vs buoy	Correction	Error before	After	Cut
Banzai PipelineHawaii	51201	+0.73 ft	-0.73 ft	1.25 ft	1.01 ft	−19%
Hanalei BayHawaii	51208	-0.75 ft	+0.75 ft	1.15 ft	0.88 ft	−24%
Honolua BayHawaii	51205	-2.34 ft	review	2.57 ft	—	—
MakahaHawaii	51212	-0.06 ft	+0.06 ft	0.65 ft	0.64 ft	−0%
Sunset BeachHawaii	51201	+0.73 ft	-0.73 ft	1.25 ft	1.01 ft	−19%

Puerto Rico

Spot	Buoy	Bias vs buoy	Correction	Error before	After	Cut
Aguadilla (Wilderness)Puerto Rico	41115	+0.22 ft	-0.22 ft	0.59 ft	0.54 ft	−7%
Rincón (Marías)Puerto Rico	41115	+0.15 ft	-0.15 ft	0.57 ft	0.56 ft	−3%
San Juan (La Ocho)Puerto Rico	41053	-0.53 ft	+0.53 ft	0.75 ft	0.53 ft	−29%

West Coast

Spot	Buoy	Bias vs buoy	Correction	Error before	After	Cut
C Street (Ventura)California	46053	-0.52 ft	+0.52 ft	1.02 ft	0.88 ft	−14%
El Porto (Manhattan Beach)California	46221	-0.71 ft	+0.71 ft	0.90 ft	0.55 ft	−39%
Huntington Beach PierCalifornia	46222	-0.03 ft	+0.03 ft	0.65 ft	0.64 ft	−0%
Lower TrestlesCalifornia	46224	-0.18 ft	+0.18 ft	0.54 ft	0.51 ft	−6%
Malibu (First Point)California	46221	-0.40 ft	+0.40 ft	0.66 ft	0.52 ft	−21%
Mavericks (Half Moon Bay)California	46012	+0.26 ft	-0.26 ft	0.98 ft	0.94 ft	−4%
Ocean Beach (San Diego)California	46225	-0.15 ft	+0.15 ft	0.60 ft	0.59 ft	−3%
Ocean Beach (San Francisco)California	46026	-1.08 ft	+1.08 ft	1.40 ft	0.89 ft	−36%
Pismo Beach PierCalifornia	46011	-1.29 ft	+1.29 ft	1.61 ft	0.96 ft	−40%
Pleasure Point (Santa Cruz)California	46042	-2.22 ft	review	2.39 ft	—	—
RinconCalifornia	46053	-0.47 ft	+0.47 ft	0.96 ft	0.84 ft	−13%
San Onofre (Old Man's)California	46224	-0.18 ft	+0.18 ft	0.54 ft	0.51 ft	−6%
Steamer Lane (Santa Cruz)California	46042	-1.72 ft	+1.72 ft	1.92 ft	0.85 ft	−56%
Swami's (Encinitas)California	46225	-0.65 ft	+0.65 ft	0.88 ft	0.59 ft	−33%
BandonOregon	46015	-0.84 ft	+0.84 ft	1.25 ft	0.93 ft	−26%
Otter RockOregon	46050	-1.13 ft	+1.13 ft	1.39 ft	0.81 ft	−42%
Pacific CityOregon	46050	-1.10 ft	+1.10 ft	1.36 ft	0.80 ft	−41%
Pistol RiverOregon	46015	-0.42 ft	+0.42 ft	1.15 ft	1.08 ft	−7%
Seaside CoveOregon	46029	-0.95 ft	+0.95 ft	1.23 ft	0.78 ft	−36%
La Push (First Beach)Washington	46041	-0.60 ft	+0.60 ft	0.96 ft	0.74 ft	−22%
Westport (The Cove)Washington	46211	-0.64 ft	+0.64 ft	0.98 ft	0.74 ft	−25%

Method: predicted combined offshore significant height vs. the buoy's reported WVHT, paired on the hour, ~20 days of live forecasts vs NDBC buoys (Aug 2026, summer regime). "After" is the error with each spot's constant bias removed (√(RMSE² − bias²)). Buoys verify the incoming wave energy and its calibration; the breaking-height transform itself is checked against cams and reports over time. Corrections are re-fit each season. Raw numbers, live: /api/skill.