What is a GRIB?
Gridded Binary data files (GRIB) are output files generated by computer forecasting models. They are tremendously more compact than regular weather charts and because of their size are very well suited for download via wireless means. The largest producer of GRIB weather is NOAA although other organizations
such as the military and research institutions also generate GRIB files. NOAA GRIB files are the best ones suited for marine forecasts.
Be aware that these forecasts are published without human intervention. Human forecasters do not review the data before it's published and therefore some knowledge and awareness is required by the end user. Also note that NOAA uses several models to generate GRIB files and it is the users responsibility to know
the strengths and weaknesses of each forecast model before using them to plan their travels.
It is best to familiarize oneself with the GRIB files from each model for the area you travel in and compare these forecasts with other reliable weather sources before depending on them to make predictions. You will find that GRIB forecasts can be extremely accurate and in remote parts of the world possibly
the only source of weather forecasting. We have had reports from users in the Beagle channel in South America that claim that the GRIB forecasts received from GMN are "spookily accurate". None the less a keep in mind that a forecast is a "forecast" and forecasts have been known to inaccurately predict the future.
GMN produces 7 day GRIB forecasts for the entire world. The GRIB files are generated at 0015, 0615, 1215, 1815 GMT everyday.
Click here to view instructions on receiving GRIB weather files via e-mail.
GFS/AVN vs. Wwave3 GRIB Files
NOAA produces two GRIB formats suitable for Ocean wind forecasts. These GRIB formats are produced by the Global Forecast System known as GFS/AVN and the wave watch model know as wwatch3. Both models generate similar forecasts but there are a few differences enumerated below:
Wwave3
- Generates wind forecasts at Sea Level taking into account wave and current
effects.
- Forecasts are only for Ocean waters. The model does not generate forecasts
for interior bodies of water such as the Mediterranean, Baltic, Black Sea, and
Great Lakes.
- Does not forecasts winds over land. This results in smaller GRIB
files which is a tremendous advantage to wireless users.
- Generates forecasts for significant wave height, mean wave direction, mean
wave period, peak wave period, peak wave direction, wind sea direction, and
wind sea period.
- Forecasts are produced in 3 hour intervals for 7 days (168 Hours).
- Model is run 4 times a day.
- Data generated on 1x1.25 degree grids.
GFS/AVN
- Produces wind forecasts for the globe (Ocean and Land) at 10m. Wave action
is not taken into effect.
- Forecasts are produced in 12 hour intervals to 7 days and then in 24 hour
intervals to 14 days.
- Generates forecasts for pressure at mean sea level, 500 mb pressure
height, surface temperature at 10m, relative humidity, precipitation, plus
much more.
- Model is run 4 times a day.
- Data generated on 1x1 or 2.5x2.5 grids.
GMN GRIBs
GMN uses wwave3 GRIB data to generate Ocean wind and wave forecasts and GFS/AVN
for pressure, temperature, 500mb. As a public service GMN delivers wwave3 wind
forecasts at no charge via ftp, http, and email. No subscription is
necessary to access the wind GRIB files. Users wishing additional data
should consider using our premier data download product WeatherNet.
Advantages of GMN GRIB over other providers
- GMN GRIB files are considerably smaller. Almost by a factor of 2.
- More forecasts are packed into the files. You get forecasts for every 6
hours vs. 12 hour forecasts for most others.
- E-Mail robot syntax is simpler supporting custom regions and automatic
scheduling.
- Wwave3 GRIB files used for wind forecasts.
The only disadvantage wwave3 has over GFS/AVN for wind forecasts is that it
does not create wind data for interior bodies of water such as the Med, Baltic,
Black Sea, etc... For these you will have to use the GFS/AVN GRIB files.
Note: The GMN mail robot will send you wwave3 GRIBs if you request a custom region
or one of the static regions which does not contain an "interior" body of water.
If your request a static region which contains an "interior" body of water such
as the Med or Great Lakes you will receive an AVN GRIB file.
Viewing GRIB Weather
GRIB files downloaded with WeatherNet or via
e-mail can be viewed on a number of different commercially available viewers.
OCENS offers a full featured viewer call GRIB Explorer. Learn more about GRIB
Explorer on our GRIB Explorer page.
An alternative to GRIB Explorer is a simple, cost effective, and
comprehensive GRIB viewer is WindPlot by Xaxero software LTD. A full description of
WindPlot and it's features can be viewed on our
WindPlot web page.
Need to know more about weather forecasting with GRIB files? Check out
Chris Parker's "Coastal and Offshore Weather, the
Essential Handbook".
Testimonials
Jonathan Selby - S/V Anahera
I have been using this quite a lot in the Cape Horn area and when you use
the data sets provided by Global Marine Networks, the
data has been found so accurate it is spooky.
Dave Holmes - Schooner Adventure
[I] downloaded the grib viewer and the West Atlantic file yesterday. I am
VERY impressed! We are laying over at Cape Fear due to a gale, the progress of
which is predicted over the next week.
Download GRIB files by region
The following is a list of supported regions. Click on the Key to download a
compressed 7 day wind forecast for the selected region.
Note: Internet Explorer users will need to right click the appropriate link
and select "Save Target As..." to download the file.
To view GRIB files you will need the following
- A program to uncompress the compressed GRIB files.
- A GRIB viewing program.
Visit our download page if you do
not have these.
Purchase GRIB Explorer
For your convenience your account will be set to automatically renew. You will receive an email alerting you of this process one week before your next renewal. If you would like to stop the subscription at that time, please notify us via email.
GRIB Explorer Software
$199 Download version
$210 Shipped on CD
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Purchases our WeatherNet Data Package with GRIB Explorer
With "GMN's Weather Data Package" you will have all you need for unprecedented access to weather and ocean data, and the power of GRIB with just one click.
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Last modified: 02/11/09
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