  We report the observation of a cloud system on Titan that remained localized
near 40S latitude and 60W longitude for at least 34 hours. Ground-based
observations obtained with the SINFONI imaging spectrograph at the Very Large
Telescope over 4 consecutive nights recorded the lifetime and altitude of the
unresolved cloud system. Concomitant measurements made by Cassini/VIMS over 3
hours resolved changes in the altitude and opacity of individual regions within
the system during this time. Clouds are measured from 13 to 37 km altitude with
optical depths per pixel ranging from $\tau$=0.13 to 7. Short timescale rise
times are consistent with previous measurements of the evolution of
mid-latitude clouds; however the long timescale localization of the cloud
structure is unexplained. We speculate about the role of meso-scale circulation
in relation to cloud formation.
