Source : Webster's Revised Unabridged Dictionary (1913)

Northwesterly \North`west"er*ly\, a.
   Toward the northwest, or from the northwest.

Source : WordNet®

northwesterly
     adj 1: coming from the northwest; "northwesterly winds" [syn: {northwest}]
     2: situated in or oriented toward the northwest [syn: {northwestern},
         {northwest}]