You posed the question of whether Katrina was God's judgment because of the obvious coincidences in its timing related to the Gaza pullout that America caused to happen starting with Oslo over 10 years ago, and the Southern Decadence event scheduled for immediately after Katrina hit.  I've written an article to cover whether this event fits the biblical model of God's judgment or a "curse" of God, such as withholding the blessing of "rain in due season" and giving the curse of too much rain where it's not wanted such as with a hurricane!  Hope this helps:
 
Hurricane Katrina and New Orleans: God's Judgment For Gaza?
http://www.escapeallthesethings.com/katrina-new-orleans-hurricane.htm
Kind Regards,

Tim McHyde
http://www.EscapeAllTheseThings.com
Sharing the Plainterpretation of Bible Prophecy since 2000