If a 1-megaton nuke releases 4.18*10^15 joules in 5 seconds, that is 836 trillion watts. The hurricane releases energy at a rate of 1.5 trillion watts. So it might be said that the bomb is actually 557-times more powerful than a hurricane. But even moreso, while a hurricane may be 1000 km in diameter (785,000 sq.km) the 1-megaton bomb will cause significant damage to structures in an area up to 25 km in diameter (491 sq.km) and leave a half-kilometer deep, 4-km wide crater at ground zero. Also, a huge area 400+ km downwind will be dangerously radioactive due to fallout for 2-3 years. A nuclear bomb is abnormally destructive. The reason for the extent of devastation in New Orleans is not due to the hurricane, but because they built below sea level. Once the dykes broke, the inrushing water did the rest, even after the hurricane had passed.