NCEP/GFS Version Update 12 June, 2019 at 1200 UTC

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kwerner

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If you do not use the GFS forecast product, this email probably does not concern you. If you do, please read on.

As you may be aware, NCEP is upgrading GFS from version 14 to 15.1 beginning with the 1200 UTC run on June 12, 2019. At that time, there will also be a change with the real-time data product. This includes available pressure levels, file size, and the data directory structure. For the data directory change and the full description of the GFS upgrade, please see https://www.weather.gov/media/notification/scn19-40gfs_v15_1.pdf

To handle the new GFS data, you must use the ungrib program from WPS V4.0 or later. You do not need to upgrade other programs to later versions. The output from the newer ungrib will work with metgrid and the WRF model from earlier versions. To do so, you can download WPS Version 4.0 or later, place it in appropriate directory, then type 'configure' and 'compile ungrib'. This will only build the program ungrib.exe. After you run metgrid, check the values for 'num_metgrid_levels' using ncdump. If you do not use the supplementary pressure level data, num_metgrid_levels will change (from 32) to 34 with the new data. You can also use the new namelist option pmin (unit Pa) for ungrib to limit the pressure level data ungrib processes. If you set pmin = 1000, then you will get 29 pressure levels.
 
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