If you thought the sight of the great American jazz city New Orleans flooded to the eaves -- its people trapped in attics or cowering on rooftops -- was the nightmare hurricane scenario, think again. Max Mayfield, director of the U.S. National Hurricane Center, says there's plenty of potential for a storm worse than Hurricane Katrina which killed 1,339 people along the U.S. Gulf coast and caused some $80 billion in damage last August. "People think we have seen the worst. We haven't," Mayfield told Reuters in an interview at the fortress-like hurricane center in Florida. "I think the day...