The National Oceanic and Atmospheric Administration (NOAA) plans to participate in the PAN-GASS Grey Zone model comparison activities by performing and contributing simulations of the boundary layer and cloud structures observed in EUREC4A. This poster presents results of tropical boundary layer simulations using the MYNN-EDMF (within the context of the RAP/HRRR physics suite) to investigate the sensitivity of the morphology of shallow cumuli. Sensitivity tests are performed by activating/deactivating certain components, such as the momentum transport, cloud-radiative feedbacks, etc. Sensitivities, successes and remaining challenges are identified for further research. This poster is meant to instigate interesting conversation on the important processes involved in evolving fields of shallow-cumuli and their representation within the model physics, which are important for regulating the structure of the tropical boundary layer.