It was unusually wide, according to NASA, and the broad swath of ocean swells it created turned into a "massive, unrelenting" storm surge that flooded the coast and left 80 percent of New Orleans underwater.
Five years later, the city is still recovering --just last week, Smart Planet wrote about the high rate of childhood asthma in New Orleans, which is caused by all the mold that developed in Katrina's wake.
This video from NASA/Goddard Space Flight Center in Maryland includes the dramatic image above -- it's a picture of what fueled Katrina, the relentless warming of the Atlantic Ocean in the weeks leading up to the hurricane.
The video opens with Atlantic Ocean sea surface temperatures data from an instrument called AMSR-E (Advanced Microwave Scanning Radiometer - Earth Observing System) that flies aboard NASA's Aqua satellite. Warm ocean waters (of 80 degrees Fahrenheit or warmer) provided energy to fuel the growing storm. Next, the MISR (Multi-angle Imaging SpectroRadiometer) instrument on NASA's Terra satellite captured the growth of cloud tops in the gathering storm.
Just before landfall, the Tropical Rainfall Measuring Mission (TRMM) satellite data revealed "hot towers" hidden within the hurricane -- powerful thunderstorms that helped intensify Katrina. TRMM also captured data on rainfall amounts throughout the hurricane's lifecycle.
Finally, the video shows Landsat satellite imagery of New Orleans before and during the flooding, as well as a more recent view of a city still rebuilding from the hurricane some five years later.
Katrina was so destructive that there will never be another one -- NASA notes that the World Meteorological Organization, which names hurricanes, has retired the name Katrina from its list.