Good comments Righty. Motiv equipment has been very good for us. For my girlfriend, her Sigma Tour isn't quite "Storm-like". It still picks up in the midlane and makes a nice strong move to the pocket.
If the shot is a typical medium THS, the Sigma Tour can be utilized with much success by most bowling styles. If your reve rate is a little on the higher side, the QZ2 Backdraft (hybrid) is an outstanding ball.
If you see a little more oil or have lower revs, the Raptor P7 is a good ball for that. Another option is the new hybrid 2Cruel. Before she got her 2Cruel in June, all we heard was how strong the ball was. For her, it isn't as strong as the Sigma Hybrid, but does have a stronger move on the back-end. Seems to be a good replacement for her favorite ball of all time, the Virtual Gravity. That is the best comparison to a popular ball I can make for the 2Cruel. Not super strong like a Nano or Mission X or Nexxus, but more than enough for most medium-medium heavy THSs.
Out of the other balls, the QZ2s are good rolling medium light-light balls and the Primal Impulse is later and stronger than the QZ2s.