GFS 0.25° Model Output to be Added to CONDUIT

National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) model output with 0.25-degree resolution will be added to the Internet Data Distribution (IDD) CONDUIT data stream on July 28, 2015.

Update: GFS 0.25-degree output is now available via the CONDUIT data stream.

NCEP began producing the GFS model output with a 0.25-degree resolution for use in weather forecasting operations in January, 2015. Unidata Program Center staff have tested the 0.25-degree GFS model output internally and have been working with operators of top-level IDD relay sites to ensure that they have the capacity to handle the increased data volume associated with this new data stream. The approximate volume of the 0.25-degree GFS model output is 20 GB per model run, four times each day. For comparison, all of the current GFS model output delivered via CONDUIT (GFS 0.5-degree, 1-degree, and 2.5-degree) total approximately 5 GB per model run, four times each day.

In the spring of 2015, the Unidata Program Center surveyed the community to determine whether there was interest in receiving the 0.25-degree output. That survey revealed significant interest from community members in receiving the data stream via CONDUIT, in addition to making it available via remote-access servers like the THREDDS Data Server (TDS).

What You Need to Do

If you operate an IDD site — either as a relay for other sites or simply to receive data locally — you may need to adjust your Local Data Manager (LDM) ldmd.conf (LDM configuration) file. The adjustments you'll need to make depend on your situation and whether you want to receive all, some, or none of the GFS 0.25-degree output. In most cases, you will not need to adjust your pqact.conf (pattern action) files. One exception would be if you want to store the GFS 0.25-degree output in a location different from where you are storing other GFS output. Contact support-conduit@unidata.ucar.edu if you have questions about the necessary changes.

Note: In the configuration file entry examples below, upstream.host.name should be replaced with the host name of the system from which you are receiving CONDUIT model output.

If your site wants the full GFS feed

If you want to receive all of the GFS feed, including the 0.25-degree model output, you will need to adjust your configuration files to include something like the following:

ldmd.conf file
REQUEST CONDUIT "GFS" upstream.host.name

If your site is already receiving the GFS 0.5-degree, 1-degree, and 2.5-degree output, your ldmd.conf file should already have an entry similar to this.

Note: If you are currently receiving the full GFS feed and have a line like the one above in your ldmd.conf file, you will begin receiving the 0.25-degree output as well (approximately 20 Gb per model run) on July 28th. If you do not want the 0.25-degree output flowing to your system, you must modify your ldmd.conf file as shown in If your site doesn't want any of the GFS 0.25-degree feed below.

If your site wants only the GFS 0.25-degree feed

If you want to receive the GFS 0.25-degree model output, but no other GFS output, you will need to adjust your configuration files to include something like the following:

ldmd.conf file
REQUEST CONDUIT "gfs.*0p25" upstream.host.name

If your site is already receiving the GFS 0.5-degree, 1-degree, or 2.5-degree output, your ldmd.conf file may have one or more entries that need to be removed to ensure that you receive only the 0.25-degree output.

If your site doesn't want any of the GFS 0.25-degree feed

If your site is already receiving the GFS 0.5-degree, 1-degree, or 2.5-degree output, but you want to make sure you don't receive any of the GFS 0.25-degree model output, you will need to adjust your configuration files to include something like the following:

ldmd.conf file
REQUEST CONDUIT "ncep/[^G]" upstream.host.name
REQUEST CONDUIT "gfs.*[012]p[^2]" upstream.host.name

This scenario requires two entries: one to request all of the CONDUIT data stream that is not GFS output (the first line), and one to select GFS output that does not match the pattern specific to 0.25-degree output (the second line).

If your site wants a portion of the GFS 0.25-degree feed

If you want to receive some, but not all, of the GFS 0.25-degree model output, your ldmd.conf file will have to include a line that filters the data stream to select only the projects you want. For example, if you want to receive just the analysis fields (which total only 170 MB per model run), you would adjust your configuration files to include something like the following:

ldmd.conf file
REQUEST CONDUIT "gfs.*0p25\.anl" upstream.host.name

Of course, the filtering pattern will have to be adjusted to reflect the portion of the full feed you want to receive. Information about building LDM pattern actions for NCEP data streams is avaiable at Internet Data Distribution of NWS/NCEP Model Products. You can also contact support-conduit@unidata.ucar.edu for assistance in creating an appropriate pattern action for your situation.

Remote Access Options

Description
GFS 0.25-degree output in IDV Data Chooser

If you do not operate an IDD site, you can still get access to the GFS 0.25-degree model output via a THREDDS Data Server thredds-jumbo.unidata.ucar.edu at the Unidata Program Center. Point your browser to one of the following GFS 0.25-degree catalogs:

If you are using the IDV, GFS 0.25-degree model output is available in the default catalog under “GFS Quarter Degree Forecasts.” (Click on the image at right to expand.)

For an example of how to use Python and Unidata's new Python library siphon to access the GFS 0.25-degree model output from the TDS, see this iPython notebook created by UPC developer Sean Arms.

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