A Numerical Simulation of the Rapid Weakening of Typhoon Trami (2018) using the Dynamical Initialization with the Assimilation of Relative Humidity Reproduced From T-PARCII and Himawari-8 Satellite Imagery

The present study investigates a rapid weakening (RW) of Typhoon Trami (2018) using the Weather Research and Forecasting V4.2 with the three-dimensional Price-Weller- Pinkel ocean model. To better represent the initial conditions of Trami, the dynamical initialization method with the assimilation process of relative humidity (DI-ARH) which is reproduced from Tropical Cyclones-Pacific Asian Research Campaign for the Improvement of Intensity Estimations/Forecasts dropsonde data and Himawari-8 satellite imagery is applied. In this study, dropsonde data obtained from Typhoon Lan (2017) is also utilized. The numerical results show that tropical cyclone (TC) forecasts can be improved in the DI-ARH experiment compared to the National Centers for Environmental Prediction Global Forecast System forecast field. Meanwhile, as the translation speed of Trami significantly decreases around the recurvature point, it longer interacted with this ocean cooling area. During this period, Trami rapidly weakened from category 5 to category 2 Saffir-Simpson hurricane scale. In the TC inner-core area, this substantial upwelling brought about a stable boundary layer and significant asymmetry in surface heat fluxes and convective clouds. Besides, the inner-core convective cells also considerably dissipated. Consequently, Trami experienced the eyewall replacement cycle, and formed a greater eye structure compared to before RW. After RW, Trami maintained almost the same intensity. More analyses will be presented in the 36th Conference on Hurricane and Tropical Meteorology.