| Darthslash |
No, they are not immune to weapon damage.
Whirlwind Exert wrote:
Creatures trapped in the whirlwind cannot move except to go where the whirlwind carries them or to escape the whirlwind. Trapped creatures can otherwise act normally, but must succeed on a concentration check (DC 15 + spell level) to cast a spell. Creatures caught in the whirlwind take a –4 penalty to Dexterity and a –2 penalty on attack rolls.
As far as the swarm spell goes. Idk. That might be a judgment call from your GM. A powerful wind like inside the vortex might disrupt the swarm while its inside the vortex, but I don't think it would cause any damage to the swarm. It might just have to reform after getting out.
Its written that fine and diminutive swarms are affected by high winds, but those are the type that blow in a single direction, a vortex would just spin them around until they get released or the vortex ends.