Multi-scale interaction and predictability of moist convection and tropical cyclones

Predicting tropical cyclone intensity changes, especially the onset of rapid intensification, has been a more challenging topic than tropical cyclone tracking because of its chaotic nature in multi-scale physical process with significant contributions from convective-scale phenomena. Before intensification onset, tropical cyclones experience precession process, in which tilted vortices rotate counterclockwise around the center of circulation, and develop an axisymmetric structure. The forecast uncertainty in precession process limits the predictability of early-stage development and intensification of TCs.

In this study, we have explored the contribution of moist convective activity to the predictability and variability of TC intensification onset through the precession process. Our recent investigation in Minamide and Posselt (2022) proposed a Lagrangian-based approach to identify the potential signals of individual convective occurrence. Using the technique, we conducted sensitivity experiments to control specific convective activities within the inner-core of early-stage TCs with convection-permitting Weather Research and Forecasting model (WRF-ARW). The results indicate that the spatiotemporal variability of convective activity even governs whether early-stage vortex completes precession and initiates RI, indicating the importance of accurately constraining convective activity in the severe weather event predictions. Given the strong nonlinearity of the onset process of RI, the advancement of our understanding of the uncertainty sources will provide an insight about the observation network that may effectively constrain the TC forecasting.