Hurricane Katrina: Just how much energy is in a hurricane?

From Hurricane Power:

Fact: The total energy released through cloud and rain formation in an average hurricane is equivalent to 200 times the worldwide electrical generating capacity.

And then there's this prediction from Hurricane Effect on Coastal Erosion:

A catastrophic scenario for New Orleans would be a direct hit from a Category 5 hurricane. Hundreds of billions of gallons of lake water would pour over the levees and into the city. That would turn the city and the east bank of Jefferson Parish into a lake as much as 30 feet deep. According to LSU Engineer Joseph Suhayda, a catastrophic hurricane represents 10 or 15 atomic bombs in terms of the energy it releases. Hundreds of thousands of people could come to home to nothing but rubble.

Update: This is getting serious (caps left as reported):

URGENT - WEATHER MESSAGENATIONAL WEATHER SERVICE NEW ORLEANS LA413 PM CDT SUN AUG 28 2005

...EXTREMELY DANGEROUS HURRICANE KATRINA CONTINUES TO APPROACH THE MISSISSIPPI RIVER DELTA...
...DEVASTATING DAMAGE EXPECTED...

MOST OF THE AREA WILL BE UNINHABITABLE FOR WEEKS...PERHAPS LONGER. AT LEAST ONE HALF OF WELL CONSTRUCTED HOMES WILL HAVE ROOF AND WALLFAILURE. ALL GABLED ROOFS WILL FAIL...LEAVING THOSE HOMES SEVERELY DAMAGED OR DESTROYED.

THE MAJORITY OF INDUSTRIAL BUILDINGS WILL BECOME NON FUNCTIONAL.PARTIAL TO COMPLETE WALL AND ROOF FAILURE IS EXPECTED. ALL WOODFRAMED LOW RISING APARTMENT BUILDINGS WILL BE DESTROYED.

CONCRETE BLOCK LOW RISE APARTMENTS WILL SUSTAIN MAJOR DAMAGE...INCLUDING SOMEWALL AND ROOF FAILURE.

HIGH RISE OFFICE AND APARTMENT BUILDINGS WILL SWAY DANGEROUSLY...A FEW TO THE POINT OF TOTAL COLLAPSE. ALL WINDOWS WILL BLOW OUT.