Source : Webster's Revised Unabridged Dictionary (1913)

Southeastward \South`east"ward\, Southeastwardly
\South`east"ward*ly\, adv.
   Toward the southeast.

Source : WordNet®

southeastwardly
     adv : in a southeastward direction; "the river flows southeastward
           to the gulf" [syn: {southeastward}]