There’s literally no wa that can do this. The only thing you can do is look out for the blue whirl your character gets that appears right before the comet launches.
Frost’s 2 PC is strong, but it’s not superior to the other dps specs by any means once it acquires it, namely because it is feasibly impossible to Shatter every single Comet, and the Comet can whiff (like the talent). FYI even if you hypothetically shatter every single comet you don’t out DPS them.