Jabes.plays.RPG says:
Ok, I'll let the post stand then. Thanks!
Note that, as far as you the player knows, there is no opponent left in initiative order who has not gone yet.
So, are you:
- doing the Thunderwave now, on your initiative, and then floating up to observe, then floating down again
- doing the Thunderwave now, on your initiative, and then floating up to land upstairs
- doing the Thunderwave now, on your initiative, and then seeking cover downstairs
- reserving Thunderwave as a triggered action, to go off if an enemy appears and attacks you before the end of this round?