Multi-scale Interaction and Predictability of the Tropical Cyclone Intensification Onset

Predicting tropical cyclone (TC) intensity changes, especially the onset of rapid intensification, has been a challenging topic given 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 the development of individual convective activity. Using the technique, we conducted sensitivity experiments to investigate the impacts of specific convective activities within the early-stage TCs on the subsequent intensification process. The results indicate that the convective-scale features of moisture distributions in TC inner-core region is essential in initiating the intensification process. Lack of specific convective activity can even govern whether early-stage vortex completes precession and intensify. 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.