On the level Storm, go to where the first anti-air Wraith tank is located. In the that area, on the ground on the far side from where you enter, is a large gray cylinder.
Take a vehicle and push a large crate to the side of it. Jump on the crate, then the silo. The skull is on the top of the silo.
The Catch Skull is only on the silo if the Wraiths have not been destroyed; both must be functioning.
Also, if you have a difficult time acquiring the Catch Skull, make sure that you have completed the game under the Normal or higher difficulty setting; if not the skull will not spawn. Pick up the skull.
There you go, the Catch skull.
Enjoy!
