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GEPS data in GRIB2 format

This page describes the Global Ensemble Prediction System (GEPS) data available in GRIB2 format on the Canadian Meteorological Centre (CMC) HTTP data server.


The data is available using the HTTP protocol and resides in a directory that is plainly accessible to a web browser. Visiting that directory with an interactive browser will yield a raw listing of links, each link being a downloadable GRIB2 file. In practice, we recommend writing your own script to automate the downloading of the desired data (using wget or equivalent). If you are unsure of how to proceed, you might like to take a look at our brief wget usage guide.

The data can be accessed at the following URLs:


File name nomenclature

The file names have the following nomenclature:


  • CMC_geps-raw: constant string indicating that the data is from the Canadian Meteorological Centre (CMC), the model used (geps: Global Ensemble Prediction System) and the data type (raw).
  • Resolution: Constant string indicating the data resolution (0p5x0p5)
  • Variable: Variable type included in this file. To consult a complete list, refer to the variables section.
  • LevelType: Level type. To consult a complete list, refer to the variables section.
  • Level: Level value. To consult a complete list, refer to the variables section.
  • YYYYMMDD: Year, month and day of the beginning of the forecast.
  • HH: UTC run time [00,12]
  • Phhh: P is a constant character. hhh is the forecast hour [000, 003, …, 192, 198, 204, ..., 378, 384] or [000, 003, …, 192, 198, 204, ..., 762, 768] each Thursday at 000UTC
  • allmbrs: constant string indicating that all the members of the ensemble are included in this file
  • grib2: constant string indicating the GRIB2 format is used

Example of file name:

This file originates from the Canadian Meteorological Center (CMC) and contains the raw data of the Global Ensemble Prediction System (CMC_geps-raw). The data in the file start on September 1st 2010 at 00Z (2010090100). It contains the U-component wind (UGRD) at the isobaric level 925 mb (ISBL_0925) for the forecast hour 78 (P078), for all members (allmbrs) in GRIB2 format (.grib2).


Resolution 0.5 x 0.5 degree

The global ensemble prediction model runs at the source on an uniform grid at 0.5 degree. The fields included in the series of GRIB2 data are available on the NAEFS latitude-longitude grid of 720 x 361 points, covering the Earth surface at a resolution of 0.5 x 0.5 degree, which corresponds roughly to 50 km between grid points.

This table lists details of the latitude-longitude grid used in the encoding of the GRIB variables.
Grid Parameter Value of Parameter
ni 720 points
nj 361 points
resolution 0.5 degree
first grid point coordinate 90° S
000° E

Variables description

Links in the second column below (Forecast hour), provide information on which variables are included in each of the CMC GEPS GRIB2 file, along with detailed information on sections 0-6 for each of the records in these GRIB2 files.

The number of variables (or records) in the 0-hour forecast files is less than the number of variables (or records) in the non-zero forecast hours because some variables are not produced at forecast hour = 0.

This table offers links to information describing available variables
Ensemble members Forecast hour
Control member (member 0) 0-hour forecast
Non-zero forecast hours
Perturbed members 0-hour forecast
Non-zero forecast hours

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