I'll take that as a "yes" to my previous question.
Here's my suggestion:
(In the Arduino IDE) File > Preferences > Show verbose output during: > upload (check) > OK
File > New
Sketch > Upload
After the upload finishes, scroll up the black console window at the bottom of the Arduino IDE window until you find the avrdude command generated by the Arduino IDE. Copy that command and then change the .hex file name to you hw8.hex, then verify this command works.
There are a couple things that might be different between your non-working avrdude command and the Arduino IDE generated working command. The first is that the Arduino IDE's command specifies the avrdude.conf file from the Arduino IDE's avrdude tool, which might be different from the /usr/local/Cellar/avrdude/6.3/etc/avrdude.conf used by your non-working command. Also, the IDE-generated command is surely using Arduino's version of AVRDUDE, whereas your command may be using a separate version installed on your system. Arduino has a special build of AVRDUDE with some modifications.