Katy Perry's "Dark Horse," the third single from "Prism," is an out-of-the-box HitPredictor this week at both Top 40 and Hot AC. Meanwhile, Pitbull's "Timber" is crossing to its third format, nabbing a HitPredictor this week at Hot AC. It was previously a HitPredictor at Top 40, where it's currently #4, and Rhythmic, where it's #12. And by the way, this is the last HitPredictor newsletter of 2013. We will be back on January 6, 2014. Happy holidays!