We investigate the representation of individual supercells and
intriguing tornado-like vortices in a simplified, locally-refined global
atmosphere model. The model, featuring grid stretching, can locally
enhance the model resolution and economically reach the cloud-resolving
scale. Given an unstable sheared environment, the model can simulate
supercells realistically, with a near-ground vortex and funnel cloud at
the center of a rotating updraft reminiscent of a tornado. An analysis
of the vorticity budget suggests that the updraft core of the supercell
tilts environmental horizontal vorticity into the tornado-like vortex.
The updraft also acts to amplify the vortex through vertical stretching.
Results suggest that the simulated vortex is dynamically similar to
observed tornadoes and modeling studies at much higher horizontal
resolution.