Hate to say it, Tragic, but Monster Surges resolve on the current Omen because advancing the Omen is the first icon on the Mythos card... So the monsters would have shown up in London where the constellation Omen is, not Istanbul with the comet. :[
If it's any consolation, I've played this game probably ten times and only had one legitimate victory. The first time I played with a group, we beat Azathoth only because I forgot to resolve his Reckoning effect several times. This game is no joke.