Sources of weather and oceanographic data
The data referenced below is available from Saildocs, Great Circle-Squid, Tidetech or Expedition. These are the main sources of data used by the sailing community and are all available in Expedition. In addition, much data is feely available on the internet, especially for US and European waters.
Great Circle - Squid is a complete weather service with satellite images, observations and model data.
Saildocs is a free source of grib data, designed to satisfy Rule 41(c), and can be used to retrieve other information.
SailFlow is a source of weather observation data.
Tidetech is a source of specialised oceanographic and tidal data.
Expedition also has a grib server, mainly to provide data not available from Saildocs or Squid.
Expedition also has links to freely available observation and model data (MyGrib and MyImage). Expedition also supports other services such as Ocens.
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.
Weather maps and observations
Weather maps and satellite images are available from many sources, including MyImage in Expedition and Squid.
Weather observations are available from many sources, including BOM, NOAA NDBC and SailFlow in Expedition.
Windy may be the best of the online weather viewers, with GFS, ICON, ECMWF, Arôme & NAM data. It is also available as Android and Apple apps. Flowx is another very nice app and includes Expedition WRF data.
Data and sources we have found useful over many years of racing:
From experience, 0.25° is a good compromise for global model data offshore.
1/8°-1/10° data may be more useful, but file sizes will be larger. Doubling the resolution will increase file size by about a factor of 4.
Comparing models is difficult - generally the important considerations are timeliness and which is performing best on any day.
Model Accuracy can be useful to compare how different models performed during a race or at a given location. Of course past performance isn't always a good indicator of future performance.
13km resolution and 64 levels, increasing to 127 levels with GFS16 in March 2021,
Available 4x daily at 1/4° or 1/9° resolution,
10km resolution and 70 levels,
Available 4x daily at about 1/10° resolution. 06 and 18z runs are only available to 60 hours.
UK Met Office.
13km resolution and 90 levels,
Available 4x daily at 1/4° or 1/8° resolution. ICON data is generally available earlier than GFS and UM-Global,
15 km resolution and 84 levels,
Available twice daily at 0.24° or 0.15° resolution,
Environment and Climate Change Canada, licence terms.
7.5-37km resolution and 105 levels,
Available at 1/2° resolution,
Available 4x daily at 0.1° or 0.2° resolution. Expensive and available later than GFS, ICON or UM.
T681 (about 20km) and 60 levels.
US Navy model.
39km resolution and 60 levels,
Available at 1/10-1/2° resolution,
Ocean currents and sea temperature, available at 1/12° resolution,
The local government high resolution models are generally very good and are usually the default choice.
Expedition also provides WRF simulations for areas where high resolution data is not available or hard to obtain. They can be also useful as a second forecast for comparison.
NOAA HRRR, RAP & NAM
Arôme & Arpège
HIRLAM & Harmonie, FMI, KNMI & YR.no
ICON EU & CosmoDE
Expedition WRF, some areas are on demand for regattas
BSH Baltic & North Sea tidal currents
Japan, Hong Kong, Philippines
Expedition WRF, on demand
New Caledonia and Polynesia
NOAA HRRR, RAP & NAM. HRRR is very good
GLERL - Great Lakes winds & currents
Expedition has integrated current models for various areas.