Out of curiosity.
I mapped out the coordinates for a theoretical track to landfall. It appears that Katrina has started her Northward motion. Using Vortex for the Lat/ Longs.
From 0631Z to 0725Z she moved 0.20minutes North and 0.01minutes West.
These are Aircraft minutes and not decimal points.
In decimal points the last fix would convert to N 28.03333 and W 089.58334.

Plotted due North this would approximate a 'theoretical' landfall about 7 miles S of Buras,LA or 12 miles SW of Boothville,LA.

If she were to continue a due North run/ track from that point. She would make a second landfall at or near the MS/LA border at the Pearl River. This is near Lake Borgne and just south of Pearlington,MS.

ALL of the above comments are based on a "theoretical" due north track and are not implied or forecast by NHC or the NWS.
They are purely...conjecture.~danielw