The Role of the Middle Tropospheric Mesoscale Convective Vortex in the Genesis of Typhoon Durian (2001) — Simulation and Verification

Although observations suggest there is a close relationship among the western Pacific tropical cyclones (TC), the monsoon troughs and the mesoscale convective systems (MCS), few real case numerical simulations associated with MCS have been performed. In order to further examine the contribution of middle tropospheric mesoscale convective vortex (MCV) forced convectively by MCS to the TC genesis, a real case numerical simulation of typhoon Durian (2001) is completed using the PSU/NCAR nonhydrostatic mesoscale model (MM5) with a high resolution (6 km). The results show: MM5 captures successfully the location of initial formation of Durian, which has a connection with the location of MCS as indicated by previous observations; the simulated track and evolvement of intensity resemble those of the best observation report, furnishing an accurate forecast of the landfall location, and revealing the slow descending and the sharp descending in the change of central minimum pressure; the simulated radar reflectivity reproduces well the boundary between the TC cloud system and the MCS cloud system in the monsoon trough during the genesis stage, also the eye and spiral cloud bands during the mature stage; the information of MCS included in the initial conditions of MM5 is crucial to this successful simulation. Moreover, the simulation reveals the presence of middle tropospheric MCV that has a 200 km horizontal extent and is located between 800 hPa and 400 hPa with a warm core, which is similar to observations. The verifications enhance the reliability for using the high resolution simulation results to investigate the role of MCV in TC genesis.