I have been a long time lurker here and have decided to post. Hurricane Katrina if she hasnt already finished her eye wall replacement cycle, she will soon. From satellite images her outflow is looker better in all quadrants, and her core has gotten stronger. I agree with the NHC that this will be a category four hurricane, but not until she opens up her eye. Her pressure might even get down to 935 MB, but her winds will not correspondingly go up until she opens up the eye.
chances of her becoming category five?
Theres more here at play than high water temperatures. Historically hurricanes have weakened before landfall going into the North Gulf Coast. The only thing to weaken her though is shear forecasted during landfall. Most likely she will landfall as a category four 145 mph, but there is a small possibly she could strengthen to a category five. I have doubts though she could hold that intensity very long, due to her extended eye wall replacement cycle today.