Huge graphic of Katrina
This thing is massive, and ridiculously powerful. Being the weather geek that I am, I've been glued to the Weather Channel all day.
Sustained max winds of 175mph. Gusts up to 207mph. That's on par with F-3/F-4 tornados. Examples of damage from those kinds of tornados:
The lower the pressure of a hurricane, the more powerful. Andrew had a pressure of 922 mb. Camille was 909 when it made landfall. Currently, Hurricane Katrina has an even lower pressure of 902 mb.
This is one hell of a storm.