Free GRIB Viewer

Software supplied by Expedition
  • The tool to get PredictWind GRIB files. Another alternative is Adrena
  • GRIB files are downloaded to a single directory for use in other programs.
  • Compatible with all major Navigation programs including Maxsea, Deckman, Evolution, Nobletec, MapTech, Open CPN, PC Plotter, and many more...
  • See detailed help below.
  • Operating System Requirements: Windows XP/Vista/Windows 7

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View the GRIB Viewer Tutorial

GRIB Help Contents

GRIB explained

Free GRIB Viewer

Downloading and Viewing GRIB files

Tool Bar Functions


Email GRIB files (for SSB Radios)

GRIB explained
  • GRIB files are a special binary format of weather data. 
  • It is the same forecast as available on the weather forecast site, but as the files are highly compressed, it is ideal for downloading across wireless communication devices.
  • GRIB files can be displayed on most popular navigation software, and can be used for optimal weather routing.

Free GRIB viewer

An example of a PredictWind 100km resolution GRIB file for offshore passages in the free GRIB viewer.


An example of a PredictWind 1km resolution GRIB file.


Downloading and Viewing GRIB files

The Free GRIB viewer is the only way to get PredictWind GRIB files.

If you want to use the GRIB files in other Navigation/Weather display software the default directory for storing GRIB files in the Free GRIB viewer is;
Windows XP: C:\Documents and Settings\All Users\Application Data\Expedition\Grib
Vista Windows 7:  C:\program data\user-name\Expedition\Grib\

PredictWind High Resolution

Right click on the chart and select PredictWind High Resolution (you can identify the pre-defined forecast areas available on the PredictWind forecast site by the dashed blue boxes on the chart) to display a PredictWind forecast.


  • The first time you will need to enter your username (registered email address) and password. Then select 'remember password.'
  • For any location you can select the 1km, 8km, or 60km to receive different resolution forecasts.
  • By choosing to have the GRIB file compressed, you save up to 40% of the file size. Selecting 'wind only' you can reduce the file size by up to 4 times
  • Select 'clear old grib files' to clear out old GRIB files that have been loaded
  • 1km resolution GRIB files have a timestep of 1hr, and 8km/60km have a timestep of 3 hrs. Please consider this when mixing different resolution GRIB files.

PredictWind 100km resolution Custom Area.

Offshore customers can use the Free GRIB viewer to get a 9 day 100km resolution GRIB file for any location, and any specified forecast area around the world.

Simply pan/zoom the chart to set the forecast area, then select menu Weather > PredictWind 100km resolution Custom Area.


  • The first time you will need to enter your username (registered email address) and password. Then select 'remember password.'
  • You can specify the forecast length in days, the timestep, and the information you require - wind, rain, cloud, temperature, and pressure.  This allows you to get very small GRIB files depending upon your specification, to keep within your budget for communication costs.

Please note for both services you will have access to both the GFS/CMC and PredictWind forecasts. These are Proprietary PredictWind forecasts, initialized with either GFS or CMC observations.

Alternatively you can download the standard GFS and CMC forecasts commonly available on many other forecast site. This will allow you a comparison, and help you appreciate the accuracy of the PredictWind forecasts ! 

Tool Bar Functions

The tool bar along the top of the screen contains the functions most commonly used.


  • Click this button to access the weather setting page, where you can setup the default display settings of the GRIB file.
  • In addition view the GRIB files you have loaded.


Click this button to select Chart dragging mode. Drag the chart in the direction you want to pan the chart. This is the same method as Google Earth and Autocad.


To zoom in.  Alternatively use your mouse wheel.


To zoom out.  Alternatively use your mouse wheel.


Another way of zooming the chart. Select this button, and click and drag a box.

Select this button, then click on the GRIB file displayed on the chart, to view weather data for that exact location.


To select the previous time period in the GRIB weather file displayed.


A time slider that can be used to animate the GRIB weather file.


To select the next time period in the GRIB file displayed.


Displays the GRIB weather file at the current time.


After loading a GRIB file, right click on the chart, to get a graph of that exact location ( ie the point where you right click ) for Wind Speed and Direction, Air Temperature and Rainfall.



GRIB Email Service

Get 100km resolution GRIB files emailed, rather than direct via the Free GRIB viewer. 100km GRIB files are available worldwide - there are no gaps in coverage. This method of delivery suits customers who prefer to receive the GRIB files via email for SSB Radio communication.

Please Note: GRIB files via email is a popular method of receiving weather information, however we highly recommend that you consider getting weather information via the PredictWind Weather Routing via email . The information is 30-60 times smaller than the equivalent GRIB files. This will save you a huge amount on communication time and costs, and additionally show you the optimal route for speed or comfort. Click here to read more.

Recommendation:  To receive GRIB files via email, the best option is to use Expedition LT. Select menu Weather > PredictWind 100km resolution Custom Area.then click the button 'Email Request'

If you cannot install Expedition LT, please follow these instructions. Send an email to with subject ' grib ' and the following variables in the subject.

Username : your email address that you have registered with PredictWind. However if you send an email from another email address, the GRIB file will be delivered to this email address.
Password : you password that you have registered with PredictWind
Nlat : Northern Latitude of the Forecast Area you desire. No decimals allowed
Slat : Southern Latitude of the Forecast Area you desire. No decimals allowed
Elon : Eastern Longitude of the Forecast Area you desire. No decimals allowed
Wlon : Western Longitude of the Forecast Area you desire. No decimals allowed
Model : gfs or cmc - please note these are both models that are run by PredictWind, but are initialized by cmc or gfs - ie this is a unique forecast not found elsewhere on the Internet.
Time : how many days do you want the forecast? This must be between 1-9 days
Timestep : The model is run at a 3hrs time step, but by choosing 12hr time steps, you can reduce your file size. Options are 3, 6 and 12hrs
Variables : wind, pressure, temperature, rain, cloud

Please see below an example email;

Email To:
Subject: grib
username password predictwind nlat -30 slat -50 elon 150 wlon 130 model gfs time 7 timestep 12 variables wind,pressure

Please note the following checklist!

  • Spaces must separate the parameters
  • For the Latitude and Longitude values defining the forecast area, you cannot use the abbrievations N,S,E,W but you must use E = "+", W = "-", N = "+", S = "-". For example nlat S30 = nlat -30   and elon E150 = elon +150
  • Do not use other punctuation such  "=" or ' or ; or : or - between the parameters or the email will not be recognized by the GRIB server.

  • The headers such as username password Nlat etc...  must be present in the email

  • Email should be in TXT format, and not in an HTML format. Please copy the above command into Microsoft Notepad, then copy from Microsoft Notepad into the email, to ensure the text is not in HTML format.

  • The GRIB files are processed every 5 minutes, so expect this delay after making a request.

Displaying GRIB files
To display the GRIB file sent via email, select the top left toolbar  settings_1.JPG   and then select button "Add File". Select the file sent via email. Animate the GRIB file with the time slider.