The first step consists to convert the output files with radarascii2llv. It is a C program which convert ascii file in "latitude-longitude-value" file (.llv).
radarascii2llv FILE FILE.llvThen, you have to replace the field on a MesoNH grid. The values in the llv file must be considered as observations. You must use the tool obs2mesonh to convert the llv file in a diachronic file with the options ll and 2D. Then you can plot the field with diaprog, with LSPOT=T (see the section plot the fields after obs2mesonh).