nhlf90: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/nhlf90 - from package: ncl-devel

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/nhlf90 - from package: libncarg-bin

You may install the required package with command apt-get install {package}

Error in other languages:
nhlf90: bevel nie gevind nie
nhlf90: comandă negăsită
nhlf90: comando não encontrado
nhlf90: commande introuvable
nhlf90: command not found
nhlf90: käsku ei ole
nhlf90: không tìm thấy lệnh
nhlf90: komanda nerasta
nhlf90: Kommando nicht gefunden.
nhlf90: kommandot finns inte
nhlf90: komut yok
nhlf90: nie znaleziono polecenia
nhlf90: níor aimsíodh an t-ordú
nhlf90: no se encontró la orden
nhlf90: no s'ha trobat l'ordre
nhlf90: opdracht niet gevonden
nhlf90: parancs nem található
nhlf90: perintah tidak ditemukan
nhlf90: príkaz nenájdený
nhlf90: příkaz nenalezen
nhlf90: команда не найдена
nhlf90: командата не е открита
nhlf90: 命令找不到
nhlf90: コマンドが見つかりません