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Home > FTP Filter

NOAA Operational Model Archive Distribution System

Grib Filter Help


The Grib Filter is used to access a subset of a NOMADS Grib2 data file.


Grib Filter is a web application that repackages Grib2 files based on the user-selected area subset. Using Grib Filter, you may:

  • download a subset of a Grib2 dataset, or

  • generate the URL query to download a subset of a Grib2 dataset.

    This URL can be used as the quoted object of an interactive web download command, like wget or cURL. Using variables and looping, data acquisition may be customized and automated. If your script contains loops, then be sure to include a 10 second wait between fetches to protect against runaway loops and ensure responsible sharing of the server resources. Without waits between fetches, the server may mistake excessive requests as denial-of-service attack and block the user.

This application is best used for creating regional subsets of the Grib2 file.  If a selection of variable(s) and/or level(s) are needed, instead of the entire file, you are encouraged to use the partial-http transfer method to better utilize server resources.


Begin by following the "grib filter" link for the chosen model data on the main NOMADS page

Choose the date

You will then be presented with choices to traverse the directories in order to locate the desired data file.  The directory structure is not identical for each model.

First, you must choose from a list of dated directories.   For most datasets, the directory is for an entire day.  For GFS, the directory is for a single cycle of that day.  Next, you may be asked to choose a cycle.

Choose a subdirectory

For the GEFS, you are required to choose the pgrb2 directory (even though this is the only choice available).

Choose a data file

You will then be asked to choose a file from a list.  Only one file may be chosen.

Choose the Levels, Variables, and Region

You may then choose the level and variables you desire to be extracted from the file.  You may choose all, several, or none of of the displayed choices.

To define a regional subset, you may fill in the left longitude, right longitude, top latitude, and bottom latitude.

Choose to display the URL

If you want to generate the URL that describes the dataset you have defined, click the "Show the URL only for web programming" box.  When this is chosen, the filtered data file will not download, instead the URL will be displayed.  This URL can then be edited and used in a script to automate downloading the desired dataset.

Download the file (or display the URL)

Finally, the user clicks on the "Start download" button to either begin the download or display the URL.

Scripting file retrievals

You may use the URL generated in the above procedure in a script to automate your downloads using a program such as cURL. or wget
If your URL for downloading the file is=
The command line to download file to "my_file" using cURL is:
curl "" -o my_file

You may then replace parts of the command, such as the date and cycle, with a variable to build another download string in your script.

WARNING: when you loop web retrievals, please use the sleep command after every failed attempt. If the file is not available, the odds of it being available 1 millisecond later are very remote. However, polling for a file takes resources. An out of control program may poll for a files several times per second. This makes the system unavailable to people who want to do real work.



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