Investigating the dynamics of rapidly intensifying tropical cyclones in Southeast Asia

Tropical cyclones (TCs) are amongst the most hazardous severe weather events in the tropics. Forecasts of TC tracks have improved in recent years (Heming et al., 2016), enabling earlier warnings and allowing better preparations to be made ahead of landfall. However, while forecasts of TC intensity from global numerical weather predictions (NWP) models have improved, this has been slower than for TC track forecasts (De Maria et al., 2014).

Forecasting rapid intensification (RI) events, where maximum wind speeds increase by 30 knots in a 24-hour period (Kaplan and DeMaria, 2002), remain challenging for both global and regional NWP models. The mesoscale processes responsible for RI, such as eyewall replacement cycles, are not captured by operational global NWP models. Convection-permitting regional models are able to capture these processes better but struggle to predict the timing and magnitude of RI (Short and Petch, 2018).

With growing capability in high-resolution regional coupled simulations (Castillo et al., 2022) we can explore the sensitivity of RI events to atmosphere-ocean coupling. This studentship will investigate rapidly intensifying TCs in Southeast Asia, and improve our understanding of the underlying processes responsible for RI in an ensemble framework. Further, there will be analysis of the sensitivity of TC intensity forecasts to atmosphere-ocean coupling utilising convection-permitting ensemble simulations.

Objectives: The scientific objectives of the PhD project are: i. Conduct a detailed investigation into the processes that lead to rapid intensification of tropical cyclones; ii. Develop an understanding of the model's limitations and investigate ways to improve it. Potential for high-impact outcome:

The Met Office has a close working relationship with the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) and the National Center for Hydrometeorological Forecasting (NCHMF) in Vietnam. The Philippines and Vietnam are severely affected by the most intense TCs. Forecasting the track and intensity of these storms is a key challenge for NWP models such as the MetUM, in both global and regional configurations.

This project provides a way to investigate aspects of the TC dynamics in detail, to evaluate how certain dynamical processes are represented in the model with the aim of improving our ability to forecast these storms more accurately, ultimately benefiting people at risk. The project will generate results for several papers, with at least one being suitable for submission to a high impact journal.