Data: Met Office atmospheric model data on the AWS Open Data registry
(met-office-atmospheric-model-data, eu-west-2). Free, no key, CORS-enabled.
Fields are NetCDF-4/HDF5 on a Lambert Azimuthal Equal Area grid. Parsed in-browser with
h5wasm, then reprojected to Web Mercator so it aligns with the basemap.
Aimed at maritime and aviation weather: pressure with isobars, wind and gusts,
cloud base, freezing level, visibility, fog, convection, and sea state.
Contours are drawn for pressure (4 hPa), temperature (5 °C) and freezing level (1000 ft).
Go / No-Go rates each pixel GO / CAUTION / NO-GO against the thresholds for a chosen
operation, and the point breakdown names the limiting factor. Thresholds are editable
in-app (Edit thresholds) and saved in this browser; Reset to defaults restores
the built-ins. They are generic planning defaults, not authoritative — real limits come from
your SOPs, the ship's master and the aviation authority. If a required field is missing the
verdict is marked partial and must be treated as optimistic.
Waves & swell come from NOAA GFS-Wave (WaveWatch III) on a global
0.25° grid — public domain, no API key, no rate limits. The files are
GRIB2 with JPEG 2000 packing, decoded in-browser by an embedded JPEG 2000
decoder, and only the needed parameter is fetched via HTTP range requests against the
published .idx index. Fields: combined significant wave height, swell
1–3 partitions, wind waves, and their periods and directions.
Basemap: CARTO. Contains OS data © Crown copyright. Met Office data © Crown copyright.
Responses are stored in IndexedDB and reused, so reloading the page or revisiting a layer does not spend API quota. Sampled grids expire after 3 h, point forecasts after 1 h.