Satellite infrared observations have identified several common cloud top features above some severe thunderstorms occurred in the US Midwest. These include the so-called enhanced-V (a cold V-shapes region in the upstream rim of the anvil), cold area (CA), warm-cold couplet, close-in warm area (CWA), and distant warm area (DWA). Some forecasters use these features to identify the severity and the development stage of the storm. While these features have been known for some time, the responsible mechanisms for them have not been adequately understood due to the complexity of the thunderstorm cloud top processes.

In the present paper we will report an investigation of the physical mechanisms responsible for the production of these features. We performed numerical simulations of several Midwest severe thunderstorms using a deep convective storm model WISCDYMM developed by us and performed detailed analyses of both physical and dynamical processes occurred at the cloud top level. The model produced simulated storms that closely resemble the observed storms, and the cloud top temperature fields of the simulated storms contain all the satellite-observed features as indicated in the first paragraph. Analyses show that the observed cloud top features are mainly the results of dynamical processes but cloud microphysical processes may influence the magnitudes.