How to redraw screen of Vim

I sometimes jump from inside Vim to use other shell tools and jump back in. On occasion, when I jump back to Vim like this I find that some elements of the Vim screen are blank.

The screen of Vim can be refreshed or redrawn by pressing Ctrl+l. If that does not work, use the command :redraw. If even that does not work, try :redraw!.

Tried with: Vim 7.4 and Ubuntu 14.04