Snapshots of the fiducial 2D run with ξ = 2, τ = 2π, H = 0.1, and resolution 256². A vortex is formed and establishes a local entropy gradient that counteracts the global entropy gradient that caused it in first place. Moderate cooling times keep the surfaces of constant density and constant pressure misaligned, leading to more vortex growth. In the positive feedback that ensues, giant anti-cyclonic vortices grow to the sonic scale. The initial condition was free of enstrophy. This vorticity growth was due purely to baroclinic effects.