Images of T, s, (∇T × ∇s)_z, and normalized vertical vorticity for a two-dimensional run with δt_forcec_s0/R = 0.1 at an instant shortly before the second expansion wave is launched (top row), and shortly after the second expansion wave is launched (second and third row). Note the vorticity production from the baroclinic term in the second and third row, while in the top row, (∇T × ∇s)_z and ω_z are just at the noise level of the calculation. Even under our weakly supersonic conditions shock surfaces are well localized and the zones of maximum production of vorticity appear to be those in which the fronts encounter each other. Here we have used , ν = χ = 0.1c_s0R, with 512² mesh points. Only the inner part of the domain is shown.