One cannot assume it will cross the Yucatan and stay on course. Anything can happen once it encounters such a large land mass.
http://moe.met.fsu.edu/cgi-bin/mm5fsutc2.cgi?time=2007082000&field=Sea+Level+Pressure&hour=Animation
Dean kinda wobbled N lately in the sats, maybe Perry has faith in this MM5 model.