Hurricane Katrina   The track of Hurricane Katrina. The coloured points indicate its strength according to the Saffir-Simpson Hurricane scale, which ranges from Category 1 (blue) to Category 5 (red).   Graphical model showing a vertical cross-section of the air circulation, clouds, and precipitation associated with a hurricane   This close-up of the ASAR Wide Swath Mode image of the area of the sea surface associated with Hurricane Katrina's eye shows a darker, smoother sea surface, due to the lack of winds at the central area of extreme low pressure.