This system and Katrina share very little in common other than position in the Gulf at this time out. The oceanic heat content in 2005 in the Gulf was quite a bit higher than today, and Katrina did not have the decoupled center issue as it crossed south Florida as a category 1 storm.

This system is also fighting some hostile conditions to the south that will prevent it from rapidly strengthening. It has the tilted south/north core. Surge potential will be a lot less because of the windspeed (although surge most assuredly will still be an issue).

In short, Katrina is a bad comparison, Isaac is nowhere even close to that even at this point.