This paper reports on an experimental investigation of the stability of a baroclinic front, as generated by the spin- up of a differentially rotating lid at the surface of a rotating two-layer fluid. In contrast to formerly reported experiments, we consider miscible fluids in a relatively wide annular tank. In the parameter space set by rotational Froude number and dissipation (i.e. ratio of spin-down time to disk rotation time), different flow regimes are observed, ranging from axisymmetric to irregular baroclinic instable flows. These regimes adjoin the regimes found for immiscible fluids by Williams et al. (2005) in a small device. Differences are the baroclinic unstable regime for lower Froude number than reported by Williams et al. (2005) suggesting Sakai Rossby-Kelvin waves and the formation of vortices. Observations suggest spontaneous emission of inertia gravity waves, which interact with the large-scale baroclinic wave and lead to intense mixing and the rapid formation of intense cyclonic vortices.