Set directory for NPM

I'm working with git-bash on win 7. I want to develop an ember project and I am working on a thumb drive. I have set installed node on my E drive and added the path to the env vars.

 $ npm install -g ember-cli
  C:\Users\me\AppData\Roaming\npm\ember -> C:\Users\me\AppData\Roaming\npm\node_modules\ember-cli\bin\ember
  C:\Users\me\AppData\Roaming\npm\� -> C:\Users\me\AppData\Roaming\npm\node_modules\ember-cli\bin\ember
  + ember-cli@2.16.2
  updated 553 packages in 89.25s

  $ which npm
  /e/nodejs/npm

  $ which node
  /e/nodejs/node

  $ ember build
  sh.exe": ember: command not found

So I think whats happening is that npm is installing the packages on the c drive. I need to set a folder on my e drive, to make this portable. How can I do this?