From Accuweather.com:
"This is truly fascinating. Sunday, Hurricane Katrina was causing winds from 175 to 215 mph. These extreme winds were occurring in the eye wall of the storm. Now compare that to an F3 tornado which has winds from 158 to 206 mph. At full throttle Sunday, Katrina was actually more powerful. Also consider that an F3 tornado is 300 yards in diameter on average while Katrina's eye wall is 25 miles across. What this amounts to is that Hurricane Katrina has all the devastating chracteristics of a 25 mile wide tornado."
I think you need to take into consideration is that water being 1000 times denser than air has an unbelieveable moving force itself compounded along with the windspeed. This is WAY worse than an f3 tornado or mere wind alone.