1.install conda

wget https://repo.anaconda.com/miniconda/Miniconda2-latest-Linux-x86_64.sh
sh Miniconda2-latest-Linux-x86_64.sh

2.install ncl

conda create -n ncl_stable -c conda-forge ncl
source activate ncl_stable

3.download ncl script
wget http://www.ncl.ucar.edu/Training/Tutorials/WRF_Users_Workshop/Scripts/wrf_demo_getvar_all.ncl

put ncl script into the wrfout_ folder, change change f = addfile("wrfout_d01_2008-09-29_16:30:00","r") with your wrfout file name

4.run the ncl script
ncl -f wrf_demo_getvar_all.ncl > wrf_demo_getvar_all.result

5.check and compare the result:
grep wind wrf_demo_getvar_all.result