Well, Katrina was a Cat 1 when it hit Florida, so that is on the surface accurate. And too many people didn't take a "mere" Cat 1 seriously, and 11 died as a result.
ernesto has a long and unlikely road to a cat 1 hurricane before florida...its barely a tropical storm at this point with no real consistent center of circulation. i would say a decrease to a tropical wave is every bit as likely as an increase to hurricane strength before a south florida hit/brush. that said...the carolinas seem more threatened with the potential of a significant storm should ernesto hold together and get offshore and head that way.