I decided to look at old tracks to see if there was a historical precedent for Katrina... I only found nice colored maps on the NHC page for 1995 and after (and the Unysis maps were impossible to decipher), so that's what I used. Here's what I found regarding southern motion in the GOM (in case anyone cares... keep in mind I was just quickly looking at these plots, so I may have missed something):
2002-TS Edouard crossed FL at a higher lat than Katrina, but in the same WSW direction. It seemed to dissipate in the GOM... I wonder why? I'd say we can hope for the same with Katrina, but too late...
2002-TS Hanna went south on Sept. 12th
1999-TS Harvey went south before crossing FL in left to right on Sept. 20th

Where can I get readable graphics for years before 1995.