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Numerical Forecast Systems

Info on the Ensemble forecasts using the Global Spectral Model

Global EPS Report to WMO on NCEP Global Ensemble Forecast System (GEFS) pdf

At NCEP the current NCEP Global Ensemble configuration consists of runs at 00Z, 06Z, 12Z 18Z each day (available through anonymous ftp from public servers)

Three different types of forecast files are generated from each run:
A T(L)1534L64 high resolution GFS (file name for, e.g., a 24 hr fcst at 00Z is gfs.t00z.pgrb2f24) out to 10 days, after which this run gets truncated and is run out to 16 days at a T(L)574L64 resolution
A lower resolution ensemble control (T(L)574L64) that is started with a truncated T(L)1534L64 highbrid analysis and run out to 8 days, then reduced horizontal resolution (T(L)382) and run out to 16 days, labeled as (gec00.t00z.pgrb2(a/b)f24)
20 perturbed forecasts each run out to 16 days at T(L)574L64 (0-8 days) and T(L)382L64 (8-16 days) horizontal and vertical resolution. The tropical storm relocation technique has been used to re-install observed tropical storm location to model initial state. The initial perturbations are generated using Ensemble Kalman Filter (EnKF) 6-hour forecast with re-centerization. The stochastic total tendency perturbation (STTP) is introduced to enhance model uncertainty. Each perturbed forecast will be labled as gep(01/02/03...).t00z.pgrb2(a/b)f24

The examples of files given above are pressure grib files that also contain flux and surface related fields. For information and software on how to read grib format files, using different platforms, click here . If you have questions regarding the ensemble forecasts you can contact Yuejian Zhu at Yuejian.Zhu@noaa.gov
**(See Zhou et al., 2016; The NCEP Global Ensemble Forecast System with the EnKF initialization (submitted to MWR)