Source : Webster's Revised Unabridged Dictionary (1913)

Southwesterly \South`west"er*ly\, a.
   To ward or from the southwest; as, a southwesterly course; a
   southwesterly wind.

Source : WordNet®

southwesterly
     adj 1: coming from the southwest; "the winds are southwesterly"
            [syn: {southwest}]
     2: situated in or oriented toward the southwest [syn: {southwest},
         {southwestern}]