About this page
Some free GRIB services that will meet most sailors’ needs are given here with a more extensive listing of GRIB and Objective Forecasts on another page.
My main GRIB page describes what GRIB files are about and I have compiled a general review with comparisons of some services, free and commercial. Sailors, traditionally, have short arms and deep pockets ; few will pay for something that be obtained free. In this world, of course, you usually get what you pay for. The various commercial services have added facilities and, for some purposes, that may make them more useful. For example, some use meso-scale weather prediction models rather than global ones.
For free sources of GRIB data see these pages -
- Saildocs email service
- MailASail email service
- UGrib FTP service for Windows
- ZyGrib FTP service for Windows and Linux users
- Other FTP and Web Based services
The first free services required users to send an email to the supplier, the reply email containing a highly compressed data file that software on your computer translates to a chart of the elements requested. Since those early days, services have been introduced that use a program on your own computer to access GRIB files directly using File Transfer Protocol. The best known, UGRIB, is available at no charge. This makes obtaining GRIB file forecasts easier. For those for whom brand width is not a problem, there are also web based versions of GRIB data.
What is available using GRIB files by email or FTP.
The primary data source
The most-often used model is the NOAA/NCEP's global "GFS" model. Data on wind, pressure, are generally available on a 0.5 x 0.5-deg grid every 3 hours and, depending on the supplier, out to 180 hours. Data may be available on a 2.5-deg grid out to 384 hours (16 days). The range of elements available varies from service to service. The availability of the 0.5-deg data depends on availability from NOAA, and Saildocs, for example, may, on rare occasions fall back to 1-deg data and 6 hours if the 0.5-deg files are not available. Suppliers may not make all the information available to users.
Web page versions
If sufficient band width is available, the quickest way to access charts derived from GRIB coded data is through your web browser. A listing of these can be found elsewhere on this site. Some of these provide charts of wind, wave and other parameters. Others simply give wind and other data at specific points using interpolation from the grid points provided by the NCEP GFS.
The advantages of web based versions is the immediate access. the drawback is the problem in storing them for future reference such as comparison with the next forecast to be issued. Using a PDA, it may be possible to display a web page but not process a GRIB file using the viewer software. Over a mobile phone the cost of viewing charts may be too large for other than occasional use.
Other available information
COAMPS
This is a meso-scale (i.e. more detailed) regional model provided by the US Navy. Data are available for three regions: eastern Pacific, west Atlantic, and Caribbean/Central America. Forecast data are available on a 0.2 x 0.2-deg grid at 3-hour intervals out to 48 hours (72 for west-Atlantic). For best results, use a grid of 0.2-deg or multiples of that to avoid interpolation.
The areas for the available COAMPS areas are
- East-Pacific: 29N,60N,160W,114W
- West-Atlantic: 20N,55N,093W,055W
- Cent-Am and Caribbean: 00N,32N,120W,060W
WWave3
This is NOAA's WW3 wave model, data are available on a 1 x 1.25 degree grid with forecasts every 3 hours out to 180, and updated every 6 hours usually by HH+06:00. WW3 parameters are defined at http://polar.ncep.noaa.gov/waves/products.html. Wind forecasts from WW3 are only for Ocean waters. The model does not generate forecasts for water such as the Mediterranean, Baltic, Black Sea, and Great Lakes.
One issue is that WW3 data sometimes shows up late with the 00z data arriving at the NOAA server at 06:30 or thereabouts so it may not always be available.
NOGAPS
"NOGAPS" is a US Navy model and data are available on a 1-deg grid with forecasts every 3 hours to 24, then 6 hours to 96, then 12 hours to 144, and updated every 12 hours by HH+07:00. Available parameters of interest to the sailor are pressure, wind. ,The server is sometimes late which results in missing valid-times. For example, Saildocs terminates the download task at HH+07:00. There is no particular advantage to NOGAPS over GFS, it is simply being made available as a "second opinion" or a fall back if the GFS is not available.
