Whilst racing, weather data or services such as routing that are not free of charge or easily available to all boats are not allowed by Rule 41(c) (outside help) of the RRS. See Case 120 in the Case book. However, Case 120 clarifies that rule 41c may be changed for any particular race by the notice of race and sailing instructions.
What we use ...
Weather Maps and observations
It isn't all about Grib files - weather maps, satellite images and observations are at least as important.
From MyImage, observations in Expedition or Squid.
Another very good service is SailFlow.
The best data is almost always that from your local government weather agency. They have more resources and data so should have better products.
Most data is available from Expedition, Saildocs or Great Circle/Squid.
Note on resolution
Higher resolution data is generally more useful, but doubling of resolution increases file size by about a factor of 4.
From experience, 1/4° (0.25°) is a good compromise for the global models. 0.5° is often too coarse, but is an option for slow connections. The 1/8°-1/9° data will be more useful, but file sizes will be larger.
These are what we use:
US. Expedition has higher resolution 1/9° hourly data, but Saildocs is available earlier.
German. Available from Expedition at 1/4° or 1/8° hourly data.
Available from Expedition at 1/4° resolution. Data Source: Environment and Climate Change Canada, licence terms
Invariably nested inside global or larger regional models.
WRF models for areas where there isn't good high resolution forecast data available, such as NZ, UK and Cape Town. Most of Australia, Hong Kong, Japan and the Med are also covered. Some of these are on demand.
Expedition WRF mostly uses the GFS model for initialisation and boundary conditions.
The best model for Australia. Available by subscription from the BOM.
Often the best model for French waters. Available from Meteo France, Squid or link below.
HIRLAM & Harmonie
European waters. FMI, KNMI, SMHI and YR.no, available from Squid & MyGrib in Expedition or SMHI link below.
ICON EU & CosmoDE
German. Available from Squid or MyGrib in Expedition.
HRRR & NAM
US and Caribbean. Available from Saildocs and Squid.
RTOFS - Global, available from Saildocs and Squid.
MyOcean - Europe, available from Squid.
WW3 - waves
Expedition has integrated current models for various areas.
Tidetech also provides various current products.
Expedition integrated weather & oceanographic data
Expedition eGribs - GFS, ICON, GDPS and high resolution WRF models
Saildocs - GFS, WW3, NAVGEM, COAMPS & RTOFS
KNMI - Hirlam
NOAA GLERL - Great Lakes winds & currents
Norwegian weather office - Weather forecast from Yr, delivered by the Norwegian Meteorological Institute and NRK
OpenSkiron & OpenGrib
Other weather & oceanographic grib data
DWD - OpenData, COSMO & ICON
ECMWF, reanalysis & ERA Interim
Meteo France - Arpege & Arome
NOAA, RTOFS, WW3, Reanalysis, Degrib
SailFlow or SailFlow
Sailing Weather Service
Weather 4D Arome