Air elemental whirlwind

[Vaahama]

Whirlwind special attack says (page 306, bestiary 1):

... might take damage equal to the creature slam attack....

My question is is the druid in huge air ele allowed to add his power attack to this slam attack or is it the "base" slam damage only that is applyed?

[Ghostgeneral]

I would rule just the base slam damage (plus strength mod). Power attack allows one to gain a bonus on all melee damage rolls, it does not modify the damage caused by the supernatural whirlwind effect.