Weather

Sources of weather and oceanographic data

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.

Important notes

Whilst racing, services such as routing or weather data that is 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.

Case 120 clarifies that rule 41c may be changed for any particular race by the notice of race and sailing instructions.

Some data from the Exp grib server (UM, UKV, Access) is only available to registered Expedition users.

The data available through Expedition or supported third parties should not be relied on for navigational purposes. None of these sources guarantee that the data is without error and accept no liability for any damages, losses or other consequences.

See also licences and copyright notices below.

Weather maps and observations

Weather maps, satellite and radar imagery are available from many sources, including MyImage, Rainviewer and Squid in Expedition.

Weather observations are available from many sources, including BOM, NOAA NDBC and SailFlow in Expedition.

Ensemble forecasts

Ensemble forecasts are used to help understand uncertainty in forecasts.

Ensemble forecasts consist of a control run and a set of ensemble runs, in which the initial conditions and/or model physics are perturbed from the control run.

On average, each of the perturbed members will have lower skill than the control or deterministic forecast, although any individual forecast might show a higher skill.

ENS is available from Expedition and GEFS is available from Great Circle.

Grib data

Data we have found useful over many years of racing:

Global models

From experience, 0.25° is often a good compromise for global model data offshore

0.5° is usually too coarse, but is an option for slow connections,
0.1° data may be more useful, but file sizes will be larger,
Doubling the resolution will increase file size by about a factor of 4.

Most model data is available 3-5 hours after the main synoptic hours.
ICON is generally available first, followed by GFS, UM and the others.
EC HRES is the last available as it is a medium range model (the M in ECMWF).
See the approximate availability table below.

The Expedition server update status can be queried from within Expedition.

Availability

Availability

Regional models

Local government high resolution models are generally very good and are usually the default choice.

Expedition also provides WRF simulations, mainly for sailing venues where high resolution forecast data is not available.

Oceanography

Reanalysis

Copernicus
Copernicus ERA5 hourly data on single levels from 1940 to present

Licences and copyright

Licences and copyright