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?
NHC did; they had Katrina hitting the New Orleans area as a Category 4 in forecasts 60 hours before landfall.
Andrew almost completely petered out after it crossed Florida and caoused little damage when it hit land again.
Andrew NEVER dropped below Cat 4 over Florida or over the Gulf of Mexico, and it hit Louisiana as a Category 4 storm. It was not a wide storm and it hit a relatively unpopulated part of "Cajun Country" but it did severe damage in Louisiana where it did hit.
Again, as always, I suggest people have at least a vague concept of what the heck they're talking about before they post.