[Wrf-users] How to handle plot_gts_omb_oma.ncl ncl program

[moudi pascal]

Dear users, 
I would like to use plot_gts_omb_oma.ncl to measure quantities for each observation type, but  the program fails with:
fatal:NetCDF: Unknown file format
fatal:Could not open (/home/igri/WORK_DIR/gts_omb_oma_01)
(0)    Can not find the file /home/igri/WORK_DIR/gts_omb_oma_01  Will skip it

I don't understand why, since i am using  gts_omb_oma_01 in ascii format.Please help me to fix it. Find attached
 
With respect
Pascal MOUDI IGRI

PhD Student 
Laboratory of Environmental Modeling and Atmospheric Physics (LEMAP)
Department of Physics
Faculty of Science
University of Yaounde I, Cameroon 
Ecole Africaine de la Météorologie et de l'Aviation Civile (EAMAC), Niamey, Niger

Tel:+237 75 32 58 52 (Cameroon)
     +227 99 21 25 61 (Niger)
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