I agree with Glen -- I'm not sure we'll see Cat 5 status with Rita. SSTs are warm, but TCHP in the Gulf isn't THAT impressive (not anywhere near what it is in the Caribbean.
http://www.aoml.noaa.gov/phod/dataphod1/wo...W/2005262go.jpg
But how could Katrina reach cat 5 then? Notice the tongue of higher TCHP from the Cuba-Yucatan pass north-northwestward toward New Orleans... Katrina's path shows that it stayed over this deep warm water for much of it's lifetime, particularly during it's Cat 5 stage. Rita may take a path that puts it over the local minimum in TCHP located near 91-92W 25N (in fact, the official path takes it basically right over this area). Then again, SSTs are warmer in the western Gulf, so the TCHP may not be as important if the storm continues on moderate clip (in which case the depth of the warm water may not be as important I'd think):
http://www.osdpd.noaa.gov/PSB/EPS/SST/data...a/gulfmex.c.gif
Shear doesn't look to be a problem until near landfall. The 0z NAM shows a slightly less amplified upper-level trough compared to the 12z run, which seems current given that the 12z NAM was too amplified, as evidenced by
THIS GRAPHIC (blue is NAM, black is RAOB analysis). The NAM also forecasts stronger upper-level ridging relative to the GFS, and more elongated ridging versus the NOGAPS (
SEE THIS PAGE, where black is GFS, blue is NAM, and red is NOGAPS ). The recent model runs seem to indicate a more westward track the first 48 hours, followed by a sharper (more abrupt) turn to the NW ~18-24 hours before landfall.
It's also worth noting that the GFDL has been consistently forecasting Cat 3-4 status for the past several runs in the 12-18 hour forecast time. Yesterday morning, the GFDL was forecasting Rita to strengthen to Cat 4 (with ~145mb central pressure) by the time it passed Key West. Obviously, the rate of strengthening forecast by the GFDL has not verified, so I'd be hesitant in taking its forecast of Cat 4 in 12-18 hours.