Only a very naive scientist or someone utterly untrained in science would take the prediction of less hurricanes with increased warming to mean the model is faulty. (dotearth.blogs.nytimes.com)
Each El Niño varies, but it generally means less hurricanes in the Atlantic Ocean, but more in the Pacific Ocean. (hubpages.com)
So even a Cat 3 hurricane may have created the same failure results (I think there has been levee over-topping in New Orleans from lesser hurricanes which hit farther away, so I'm not sure how well it could really handle a Cat 3 or lesser storm with Katrina's path in the first place). (realclimate.org)