WRF driven by GFS Ensemble data on ORR2

GFS Ensemble data are available to download from here:

  • https://www.ncdc.noaa.gov/data-access/model-data/model-datasets/global-ensemble-forecast-system-gefs
  • Grid GENS 3
  • Start Date = End Date. Select files. I’m assuming that _00 is the “control” forecast, and _01 to _20 are the perturbed ensemble members.
  • When your data are ready to download, you will get an email notification. Click on the “Web Download” link. Each ensemble forecast member will have a link that looks something like this:
    gens_3_2017101200_00.g2.tar 03-Apr-2018 07:06 1.6G
    Right-click on the file and copy the link address. Now ssh into the ORR2 computer. Create a folder for this data, like GRIB/GENS/GENS00, and use wget with your copied link to download the data file.
  • Unpack your forecast data file using the tar command, e.g.:
    tar -xf gens_3_2017101200_12.g2.tar
  • You should now have lots of .grb2 files in that directory. You’re ready to run WRF.

The steps to run WRF driven by GENS are similar to those to run WRF with GFS, so follow this post: https://metclim.ucd.ie/2018/02/wrfv3-9-1-test-case-on-orr2/. A few differences to note:

  • link Vtable to ungrib/Variable_Tables/Vtable.GFSENS
  • ./link_grib.csh to both the gens-a and gens-b files.
  • In namelist.input, use: num_metgrid_levels = 27,

If all goes well, you should be able to run your WRF forecast. WRF doesn’t output MSLP, but you can use a code like this to calculate and plot it: