This is quite the exaggeration. It didn't even exist a week before it hit. Advisories were started on it as a Tropical depression in the Bahamas at 5PM on August 23rd, and it hit the morning of August 29th.
Katrina was a Category 1 storm when it hit south Florida. Nobody expected it to get as big or as strong as it did. Andrew almost completely petered out after it crossed Florida and caoused little damage when it hit land again. It's ridiculous to suggest that anyone had more than about 36 hours to prepare for a Cat 4/5 hurricane hitting New Orleans. New Orleans is home to over 500,000 people. Where is FEMA supposed to get 15,000 buses?
My bad. It was a little exaggeration.
http://www.tpc.ncep.noaa.gov/archive/2005/KATRINA.shtml?