Numerical Simulation of Tornadogenesis in a High-Precipitation Supercell. Part I: Storm Evolution and Transition into a Bow Echo

Abstract

Abstract A nested grid primitive equation model (RAMS version 3b) was used to simulate a high-precipitation (HP) supercell, which produced two weak tornadoes. Six telescoping nested grids allowed atmospheric flows ranging from the synoptic scale down to the tornadic scale to be represented in the simulation. All convection in the simulation was initiated with resolved vertical motion and subsequent condensation–latent heating from the model microphysics; no warm bubbles or cumulus parameterizations were used. Part I of this study focuses on the simulated storm evolution and its transition into a bow echo. The simulation initially produced a classic supercell that developed at the intersection between a stationary front and an outflow boundary. As the simulation progressed, additional storms developed and interacted with the main storm to produce a single supercell. This storm had many characteristics of an HP supercell and eventually evolved into a bow echo with a rotating comma-head structure. An analysi...