Re: [ldm-users] cnvgrib Utility Help

Cnvgrib was developed at NCEP, not NCAR. You can find the source at

Your invocation of cnvgrib is OK, program synopsis is:

cnvgrib [-h] {-g12|-g21|-g22} [-m|-m0] [-nv]
               [{-p0|-p2|-p31|-p32|-p40|-p41}]  ingribfile outgribfile

Green colour is fine, for some reason the program sets the execute bits, that does not affect the content of output file. My suggestions:

1. Check whether the output has non-zero length.

2. If you are on a Linux system, do from the command line:
  od -c ruc2anl_130_20090605_2200_000.grb | less
You should see output like this:
0000000   G   R   I   B  \0  \0  \0 001
. . . .

3. Check whether the program wgrib recognizes the file:
  wgrib ruc2anl_130_20090605_2200_000.grb

wgrib is available on Linux, if it it not on your system, use yum or apt-get, depending on distribution. Or build from source:

It is possible that the program does not know about GRIB2 fields, specific to the office that created the file. You can try

wgrib2 ruc2anl_130_20090605_2200_000.grb2

to see that all fields are listed by name, not parameter number. wgrib2 is available from the NCEP url.


On 18/04/16 01:11 AM, Michelle Serino wrote:
Hi all,

I am using NCAR's cnvgrib utility to convert grib2 RUC-Analysis data to grib1. An example of one of these data files is below:


When I run the command,

cnvgrib -g21 ruc2anl_130_20090605_2200_000.grb2 ruc2anl_130_20090605_2200_000.grb

the converting process seems to work. I get a file with an extension of "grb." However, while the file type is listed as a data file, it appears green, as an executable file. In addition, the code I am using does not recognize the file as a grb1 file. (The code only recognizes grb1 files.) The website to which I referred to use this utility ( did not list any additional options to use besides the required '-g21.' Am I missing something? This is my first implementation of the cnvgrib utility, so I apologize if I have made a naive mistake. I appreciate any help.

Best regards,

Michelle Serino

Michelle M. Serino
M.S. Candidate
Texas A&M University
Atmospheric Sciences Dept.
Eller O&M, Suite 1017
College Station, TX 77843
(484) 769-0949

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