It was reported that Katrina was highly unusal for a combination of high intensity and large size.

I would like to see hurricanes ranked according to total power. Total power could be determined by combined wind speed and hurricane size.

For example, Katrina's size could be represented by the amount of land area (square miles) which experienced catgory 4 wind speeds.

See comment #30 of: Hurricanes and Global Warming - Is There a Connection?

http://www.realclimate.org/index.php?p=181