A useful breeze and a storm are different questions
A sailing forecast can show wind within the app’s preferred band while a storm makes the outing unsuitable. The critical cap exists because the good wind number should not cancel the storm flag. The explorer lets you see that exact interaction without altering the existing scorer.
Absence of a storm code is not proof that the surrounding area is free of lightning. A selected point cannot describe every developing cell or the timing along a passage. Marine warnings and observed deterioration therefore remain independent information.
Shelter needs a plan before departure
The time needed to return depends on route, vessel, crew and conditions. The model does not calculate it. A sheltered harbour at the start does not establish that an exposed leg or a different destination offers a timely alternative if storms develop.
Do not treat the boat or an open waterfront shelter as automatically equivalent to proper lightning shelter. Use relevant official advice and the skipper’s plan for the actual situation. This guide explains why the score stops being favourable; it does not supply a universal emergency manoeuvre for every vessel.
Worked examples from the existing scorer
These complete hypothetical hours run through the same scoring functions used by the live tool. They are not observations or forecasts. The displayed effective score includes any cap.
| Example | Effective score | Verdict | Model reasons |
|---|---|---|---|
| Favourable illustrative breeze | 100/100 | GO | No model penalties |
| Same breeze, storm code | 10/100 | NO-GO | thunderstorms · NOGO cap |
| Storm and stronger gusts | 0/100 | NO-GO | thunderstorms; strong — reef down · NOGO cap |
Exact example inputs and units
temp and feels: °C; wind and gust: km/h; precipitation: mm/h; visibility: m; rain probability, cloud and humidity: %. Weather code is WMO; UV is an index. Pressure, where shown, is context in hPa and does not affect this scorer.
[
{
"example": "Favourable illustrative breeze",
"inputs": {
"temp": 15,
"feels": 15,
"precip": 0,
"pop": 0,
"wind": 15,
"gust": 20,
"vis": 20000,
"code": 0,
"cloud": 10,
"humidity": 60,
"uv": 0,
"pressure": 1010
}
},
{
"example": "Same breeze, storm code",
"inputs": {
"temp": 15,
"feels": 15,
"precip": 0,
"pop": 0,
"wind": 15,
"gust": 20,
"vis": 20000,
"code": 95,
"cloud": 10,
"humidity": 60,
"uv": 0,
"pressure": 1010
}
},
{
"example": "Storm and stronger gusts",
"inputs": {
"temp": 15,
"feels": 15,
"precip": 0,
"pop": 0,
"wind": 25,
"gust": 43,
"vis": 20000,
"code": 95,
"cloud": 10,
"humidity": 60,
"uv": 0,
"pressure": 1010
}
}
]Planning bands and the limits of the number
The existing model starts at 100, subtracts its condition penalties and applies critical caps. GO is 70–100, MAYBE 45–69 and NO-GO 0–44. A MAYBE cap limits the effective score to 64, and a NO-GO cap to 40. These are application suitability bands, not certified safe operating limits.
Rain branches are alternatives: matching probability, intensity and weather-code triggers do not mean adding the same rain penalty repeatedly. Separate factors can combine. A cap prevents benign temperature or dry weather from cancelling a critical flagged condition. Use the reasons beside the result to understand what changed.
The model requires complete numeric weather inputs. Missing visibility, rain probability or another required value returns Insufficient data; it is never filled with an invented favourable value. Local warnings, closures, equipment instructions and actual observations can change your decision even when the model returns GO.
Read the full sailing methodology and thresholds. The model and these examples were cross-checked on 18 October 2026. No physical field-test or safety certification is claimed.
Equipment and an alternative plan
Review warnings and the passage’s return options before leaving. Change the timing or stay ashore when a storm affects the plan. Follow appropriate marine and lightning guidance; a raincoat or a promising wind forecast does not resolve the storm risk.
Questions about Sailing and thunderstorms: why a favourable breeze is not clearance
Can ideal wind offset a thunderstorm?
No. The storm cap limits the effective verdict to NO-GO.
Is this a live lightning map?
No. It uses forecast weather codes.
Should I wait for rain to return?
No. Rain is not a reliable lightning warning trigger.
Sources and limits
The numeric application bands come from the existing GoNoGo scorer and methodology. External guidance is linked for its stated context; it is not presented as endorsement of this model.
Live forecast data is supplied by Open-Meteo. An illustrative model output is different from a live forecast, and a forecast is different from a local observation.