Simulations on multiple tropical cyclones event associated with monsoon trough over the western North Pacific

Abstract

AbstractIn this study, the formation of an idealized multiple tropical cyclones (MTCs) event within a monsoon trough (MT) region is investigated by using the weather forecasting model (WRF_ARW). Sensitivity experiments are conducted by specifying different initial conditions. It is revealed that both dynamical and thermodynamical conditions associated with the MT are important in triggering MTCs event over the western North Pacific basin. In the composite active years, which have a strong MT with higher ambient moisture, an MTCs event is produced. In contrast, no MTCs event occurs in the inactive years, which confirms the previous observational study. The possible pathway for the formation of MTCs event is proposed. In the active years, under favourable moist environments, the first TC is generated faster through the greater barotropic kinetic energy conversion. Once the first tropical cyclone (TC) is generated, the energy dispersion induced low‐level Rossby wave train acts as a precursor to the second TC. Furthermore, the upper‐level asymmetric outflow jet acts as a dynamical forcing to induce vertical motion, which builds up a favourable environmental condition for a second TC development. This work provides some insights into the formation of MTCs event.