How is the base score calculated?
Each run starts with a 0–100 score built from three forecast factors:
Alignment compares the direction the wind is moving toward with the route bearing. Wind speed is judged against ideal bands matched to each run's difficulty level. Wind-wave height represents the short-period bumps that make a downwind run work.
What changes the base score?
Forecast confidence
Strong blended gusts and disagreement of more than 7 mph between forecast models reduce the score. A badly crosswind or upwind route is strongly gated even when wind speed is ideal.
Waves and weather
Large swell on an exposed coast, thunderstorms, squally rain and visibility below 3 miles apply safety penalties.
Live observations
For today’s near-term windows, the closest fresh NDBC or airport observation is compared with the forecast. A difference over 9 mph or 45° reduces confidence by 10%. An agreeing observation is shown as supporting evidence.
Observed seas
A fresh nearby buoy reading above 2.5 m reduces the score; seas above 3.5 m receive a larger penalty. Readings must be under four hours old and within the configured distance limit.
Tides
Runs whose hazard notes identify reefs, shallows, channels, harbors or shorebreak receive a 10% penalty when a nearby NOAA low tide under 0.3 ft falls close to the selected window.
NWS alerts
Active marine advisories reduce today’s scores by 22%. Tsunami, hurricane, tropical-storm or gale warnings reduce them by 45%. The alert remains visible in the page banner.
Which sources are included?
Open-Meteo’s best-match, GFS and ECMWF wind forecasts form the worldwide forecast baseline. Open-Meteo Marine supplies waves, swell, sea temperature and currents; atmospheric forecasts supply rain, thunderstorms and visibility. On Oʻahu, NDBC buoys and coastal stations, Aviation Weather METARs, NOAA CO-OPS tide predictions and NWS active alerts provide additional observation and safety adjustments. Equivalent local observation feeds will be added to other regions as reliable public APIs are identified.
How are worldwide routes selected?
The catalog uses publicly documented downwind courses rather than invented point-to-point lines. Initial references include the Maliko shuttle course, the Gorge Challenge Viento course, Cape Town’s Miller’s Run documentation and the Rottnest-to-Sorrento Doctor race. Map lines are planning approximations and must not be used as navigational tracks.
What happens when a source is unavailable?
The three-model wind and marine forecast is required. Observation feeds are best-effort: stale, missing or browser-blocked readings are excluded, and the status line reports how many live observations loaded. Missing data never earns a bonus. Tomorrow and later windows use forecasts rather than pretending that today’s observation predicts future conditions.
Is the highest score a go/no-go decision?
No. It is a comparison tool, not a safety clearance. Local acceleration, currents, surf, launch access and rapidly changing weather can differ from every model and station. Check the official marine forecast and current observations, paddle with others, and use appropriate safety equipment and judgment.