Eu resolvi usando o modo passivo de FTP. Aqui está o novo comando de FTP:
#!/bin/bash
cd /home/giacomo/WRF/DOMAINS/puglia/postprd
ftp -i -n -v <<EOF
open "server"
user "username" "password"
binary
passive
cd /www.example.org/wrf
mput 2mTemp*.gif
quit
EOF
sleep 10
ftp -i -n -v <<EOF
open "server"
user "username" "password"
binary
passive
cd /www.example.org/wrf
mput 850mbRH*.gif
quit
EOF
etc...