Tempest triggers the Warhawk's passive ability, Heavy Impact, which in turn can cause a chain reaction of destruction if used in close quarters. Keeping the Warhawk out of harm's way until late in the fight will maximize his effectiveness.
Tempest hits the initial target plus additional units, friend or foe, moving in a clockwise fashion around the Warhawk.
Rank 1: hits up to 2 targets
Rank 2: hits up to 3 targets
Rank 3: hits up to 4 targets