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 or observations in Expedition or your local met office.
Another very good service is SailFlow.
US. Available from Expedition, Saildocs or Great Circle. Saildocs is available earlier, but Expedition has hourly data.
German. Available from Expedition or Great Circle.
Canadian. Also known as GEM. Available from Expedition and Great Circle.
US Navy. Available from Saildocs.
European. Expensive and can be hard to get.
French. Only available at lower resolution. Available from Great Circle, but I don't know a lot about it.
Invariably nested inside global or larger regional models.
US. One of the best for the US. Sources include Great Circle and NOAA.
Meteo France. Probably the best model for Europe and the western Mediterranean. Available from Great Circle or link below.
KNMI. Also reputed to be very good. Available from Great Circle or MyGrib in Expedition.
ICON EU & CosmoDE
Germany. A lot of people like these. Available from Great Circle or MyGrib in Expedition.
WRF models are almost a dime-a-dozen, but they can be very good. Examples include the NOAA HRRR.
The Expedition WRF is one of the best of course.
Swedish. Link below.
Norwegian. Available from MyGrib in Expedition.
Australian. Good, available by subscription from the BOM.
Expedition integrated weather & oceanographic data
Expedition eGribs - GFS, ICON and high resolution WRF models
Saildocs - GFS, WW3, NAVGEM, COAMPS & RTOFS - designed to satisfy Rule 41(c)
Great Circle - Squid - Many global & regional models. As used by the Volvo Ocean Race.
GLERL - Great Lakes winds & currents
MailASail - GFS
NOAA - GFS, GEFS, NAM, RTOFS etc
Norwegian weather office - Weather forecast from Yr, delivered by the Norwegian Meteorological Institute and NRK
OpenSkiron & OpenGrib - Regional models
Other weather & oceanographic grib data
DWD - OpenData, COSMO & ICON - Global & Europe
ECMWF, reanalysis & ERA Interim
Environment Canada - GDPS Global & North America
Meteo France - Arpege Global & Arome Europe
MeteoConsult - Europe
NCAR/UCAR Research data archive
NOAA, RTOFS, WW3, Reanalysis, Degrib
SailFlow or SailFlow - GFS, NAM & WRAMS
Sailing Weather Service - SWS, NAM and GFS
UCAR AMPS - Antarctic Mesoscale Prediction, incl NZ
Weather365 - ETA Europe
Weather 4D - Arome