Location of cloud features as a function of time as imaged by Cassini (diamonds) and ground-based amateur astronomers (dots). All longitudes in this figure and paper are western longitudes in degrees of Voyager SLS. The x-axis was inverted to have larger western longitudes on the left side. The y-axis goes from the start of storm F (27 November 2007) until its end (15 July 2008) with the start of the storm on the top. The different colors denote the storm cells F¹, F² and spot S³ as discussed in the text.