Because of the shallow continental shelf to the west and north of the Yucatan, the warm water there is deep...but past the shelf in the Bay of Campeche, while SSTs are warm, there is no deep warm water. The longer Stan remains stationary, since other conditions are expected to remain favorable, the longer Stan will intensify. And even if Stan intensifies more than currently anticipated, if the subsequent movement west is slow as predicted, then the cooler deep water will probably not support maintaining that intensity through to landfall. In fact the predicted SW path takes Stan over a pool of cooler water in the BOC with less than 10kcal/cm sq.

Having said that, the NHC forecast is for continued intensification right up until landfall, but only just to solid Cat 1. Just shows what do I know? I'd expect a more rapid intensification with pressure going down to 980-985 range today, but then back up to around 990 before landfall.

At least I was mollified to learn later that the entire time Rita's intensity was increasing, she was over the loop current, and I just didn't have a good mental visual on where that current was located (http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17041).