RTOFS Atlantic Current Model

Saildocs now supports the RTOFS/HYCOM model for Atlantic currents including detailed Gulf Stream data. The value of near-real-time currents is of course greatest for the Gulf Stream, and at this time RTOFS data is only available for the Atlantic. Available parameters include current (speed and direction), temperature, deviation from mean sea level, and salinity, all for the water surface. This data is compatible with advanced charting programs such as Deckman, Expedition, etc. and is also supported by the beta release of our "Viewfax" Grib/Fax viewer.

Data is available in two datasets, a 0.25-deg resolution file covering the entire Atlantic, and a higher resolution (0.05x0.06-deg) file covering the area of the Gulf Stream. There is one model run per day with a synoptic time of 00z, and data is usually available by 13:00 utc. Forecasts are available every 12 hours out 5 days (0,12,24...120 hours) for the 0.25-deg Atlantic dataset, and every 24 hours (0,24...120) for the higher-resolution Gulfstream dataset (limited by the available model data).

The lat-lon limits of the available areas are:
If the code "RTOFS" is used (without the "-gs" or "-atl") then Saildocs will select whichever file has the best coverage for the requested area. In the case where the requested area is completely contained in both datasets, then the "-gs" dataset is used.

As an example, to request a RTOFS grib file for 43N-34N, 078W-064W and 24, 48, 72 hours send the following message to: query@saildocs.com

send RTOFS:43N,34N,078W,064W

This will return current (speed & direction) and surface temperature for a default 0.5x0.5-deg grid, about a 4K file. This is plenty of resolution for the current vectors but not enough resolution to see the detail of Gulf Stream temperature. But most folks want temperature detail so that they can infer current, and the RTOFS data provides that directly.

To get the same data with higher resolution, add a grid-specification for example:

send RTOFS:43N,34N,078W,064W|0.2,0.2

This will return a file of 30K.

There is of course a tradeoff between area, resolution and file-size. A smaller area means a smaller file, a higher resolution (smaller grib) means a larger file. For planning, with a high-speed internet connection available, then very high-resolution (and very large) files are available, up to a grid of "0.05,0.06" and times of "0,24..120". Available parameters are "CUR" (current) and "WTMP" (water temp) which are the defaults, plus "DSL_M" (deviation of sea-level from mean) and "SALTY" (Salinity). See the "gribinfo" document (below) for info on how to use these.

To subscribe to a grib to be sent daily, change the "send" to "sub" in the above examples. The default subscription-time is 14:00 (actual run-time will be shortly after 14:05z). For example:

sub RTOFS:43N,34N,078W,064W

For more information about Saildocs see www.saildocs.com/info, and for more details about grib-files see www.saildocs.com/gribinfo (or send a blank email to: info@saildocs.com or gribinfo@saildocs.com).

"RTOFS" is an acronym for "Real-time Ocean Forecast System" which is operated by NOAA using the HYCOM model to provide high-resolution forecasts for currents and temperature. "HYCOM" is "HYbrid Coordinate Ocean Model" which is an ocean model that has been developed by a group of universities, the US Navy, NOAA, with some support from industry- see http://hycom.rsmas.miami.edu. NOAA's contribution is key, the task of turning a brilliant research project into an operational system should not be underestimated.

Saildocs is the effort of Jim Corenman, Sailmail co-founder and author of the Airmail software. Servers and support are provided by the Sailmail Association. And a special thanks to Gram Schweikert for doing the research on the RTOFS gribs, the contribution is much appreciated.

Good sailing,
(revised 2007-04-22)