  The cold diffuse interstellar medium must harbor pockets of hot gas to
produce the large observed abundances of molecular species, the formation of
which require much more energy than available in the bulk of its volume. These
hot spots have so far escaped direct detection but observations and modeling
severely constrain their phase-space structure i.e. they must have a small
volume filling factor (a few %), surface filling factors larger than unity with
large fluctuations about average and comparable velocity structure in ``pencil
beams'' and ``large beams''. The dissipation of the non-thermal energy of
supersonic turbulence occurs in bursts, either in shocks or in the regions of
large shear at the boundary of coherent vortices. These two processes are
susceptible to generate localized hot regions in the cold medium. Yet, it is of
interest to determine which of them, if any, dominates the dissipation of
turbulence in the cold interstellar medium. In this paper, we analyze the
spatial and kinematic properties of two subsets of hydrodynamical compressible
turbulence: the regions of largest negative divergence and those of largest
vorticity and confront them with the observational constraints. We find that
these two subsets fulfill the constraints equally well. A similar analysis
should be conducted in the future on simulations of MHD turbulence.
