No single weather app answers every passage question. The useful combination is an official warning and forecast, an observation to check what is happening, and a model or route tool to explore how conditions may change. These products have different update times, coverage and responsibilities.
Choose the source for the job
“Is there a warning for my sea area?”
Start with the national meteorological service responsible for the water you will cross. Use our sailing-area directory to find its marine bulletin. In an ocean passage, the WMO–IMO WWMIWS portal helps identify METAREA issuers; check the originating service for the freshest message.
“Where and when might the wind or waves change?”
Windy is useful for visual model layers and comparing forecast pictures. PassageWeather offers passage-oriented weather maps. Compare the same valid hour, variable and model run. Neither display supersedes a warning; a fine-looking grid cell is not a harbour forecast.
“What is happening now?”
Use time-stamped observations from the responsible national service, buoys and local networks. In Greek waters, POSEIDON combines observations with forecast products; in US waters, NOAA NDBC provides buoy reports. A station only represents its own location and exposure.
“How do I compare routes or work with limited bandwidth?”
PredictWind Offshore supports offshore forecast files and route planning, with features depending on subscription and connection. OpenCPN Weather Routing can compare routes using downloaded GRIB data. Routing output is a scenario, not a command to sail. Check current service terms before relying on offline access.
“Can I see navigation, tides and weather in one interface?”
Savvy Navvy combines chart-based planning with weather and tide features. Treat charts, weather model, tide predictions and safety broadcasts as different products with different update cycles; verify the official source for each critical decision.
“Where can I inspect wider ocean data?”
Copernicus Marine provides ocean data and viewers useful for wider context. Its fields are not a local marine warning service.
A repeatable five-minute comparison
- Open the official warning and text bulletin for every forecast area on the route.
- Record the issue time, valid time, units and next update.
- Check recent observations near, but not assumed identical to, the exposed leg.
- Use one or two model displays at the same valid hour to explore changes and disagreement.
- Write down the decision point, diversion and how you will receive the next warning.
Use the Aegean weather desk as a worked example. We may later add source-status checks and route-specific AI-assisted briefings with qualified expert review; neither is live now.
Editorial note: links reviewed 24 September 2026. These are task-based examples, not paid recommendations or an exhaustive list. Product availability, pricing, coverage and offline features can change. Always verify the latest details with the provider and use official warnings for decisions at sea.