A hurricane feeds off warm water. This NASA map of sea surface temperature shows just how warm the water was in the tropical Atlantic and the Gulf of Mexico in August 2005 when Hurricane Katrina made its way towards the Gulf Coast.

The storm began over the southeastern Bahamas on August 23 and moved over south Florida the next day as a Category 1 hurricane. The storm killed nine people and caused about $600 million in damage. As the storm traveled west over the Gulf of Mexico, the water was abnormally warm, as high as 89°F (32°C). On August 27, the storm was upgraded to Category 3 and the next day it received the highest designation, Category 5. Winds of 175 mph (280 kph) and gusts of 215 mph (344 kph) were reported. The residents of New Orleans were advised to evacuate the city and fortunately many did.

By the time Hurricane Katrina hit land it had been downgraded to a Category 4 storm. New Orleans was not hit head-on, but by the weaker side of the storm. Initial reports were that the city had been spared. What people didn’t know initially was that storm surge had collapsed several sections of the levee that protected the city. Soon 80% of the city was submerged; around 1,300 people were dead (2,500 throughout the region) and one million people were homeless.

^{Courtesy of NASA/SVS. www.nasa.gov/vision/earth/lookingatearth/h2005_katrina.html. Public Domain.}