The hand moves instantaneously, ignoring gravity. Note the description of interposing hand, which manages to interpose "regardless of how the opponent tries to get around it." This is made even clearer in the description of foreceful hand, which explicitly "has no speed limit," and will "instantly reposition itself" when necessary. The later hand spells are upgrades of IH and FH, and so share the same basic qualities.Thanks - I don't really see a flight speed in the Bigby's Hand spells. If said caster DD'd 100 feet away, does the hand have to take a round or two rounds or three to attack again?
That means if the target DDoors himself to another point within range, the hand will immediately vanish and reappear right next to him, all set to attack again on its next turn.
It's not one hundred percent clear what happens if the target leaves range. My interpretation is that it stlil interposes itself, moving to the limit of range as close as possible to the target. Obviously it can't attack from there, but since it's still in the way I allow it to grant a smaller cover bonus.