Well in 72 hours the favorable becomes unfavorable along the hit zone, assuming favorable means a stronger storm. Am I understanding that right?
Favorable means a stronger storm, yes, but keep in mind that the storm itself is unfavorable (i.e., another hurricane is not going to form inside Rita ;^). What you're seeing along the Texas coast in 72 hours is the back end of Rita. What you want to look at is the surrounding edges.
So, by example, in the 24 hour and 36 hour forecast what's important is that red strip between the Texas coast and the red/green zone of Rita. That means no wind shear to speak of - extremely favorable to hurricane intensity.
I meant orange/green zone for Rita. The typo gremlin is really after me tonight!!