A planetary-scale disturbance in a long-living three-vortex coupled system in Saturn's atmosphere

The zonal wind profile of Saturn has a singular structure in the latitude range 50oN-65oN planetocentric, with a double peak that reaches maximum zonal velocities close to 100ms-1[1]. A survey of Cassini ISS images shows that a system of three vortices formed in this latitudinal region in 2012 and has remained active until present, confirming that vortices in Saturn can be long lived [2]. In May 2015 a disturbance started to develop at the location of the triple vortex. Since at the time Cassini orbits were not favorable to the observation of the region, we were granted Director Discretionary Time of the Hubble Space Telescope to observe the region before the perturbation faded away. Here we report the dynamics and vertical structure of the three-vortex system and of the disturbance that developed at its location, based on HST and Cassini images. We also present results of numerical models to explain the stability of vortices in the region.