Identifying the key dimensions of rapid tropical cyclone intensification

Accurately predicting how fast tropical cyclones (TCs) will intensify is a major challenge due to the complex processes involved. Limited observational evidence indicates that smaller TCs tend to intensify more rapidly, suggesting a simple linear relationship between the size of the cyclone’s central core and the rate of intensification.

However, a recent study led by Dr Rong Fei of Wuxi University in China and Professor Yuqing Wang of the University of Hawaii at Manoa in the US casts doubt on this assumption. Their study, published on 7 September in the journal Advances in Atmospheric Science, was based on advanced numerical simulations and revealed that this relationship is in fact nonlinear.

Research has shown that if a tropical cyclone’s inner core size is very large or very small, it is unlikely to intensify rapidly. Instead, there is a critical inner core size that allows for the most rapid intensification. This size varies with factors such as latitude, sea surface temperature, and the initial strength of the cyclone.

The researchers found that this nonlinear relationship results from a balance between two competing processes: inward transport of angular momentum, which aids intensification, and lateral diffusion, which suppresses it.

These findings have important implications for improving tropical cyclone intensity forecasts.

“Tropical cyclones can be devastating, but forecasters believe there is a sweet spot, or a critical size, for cyclone development. If we can identify this, we can make more accurate forecasts,” Prof Wang said.

The study highlights the need to accurately determine the size of a cyclone’s inner core in forecasting models and suggests that early detection of tropical cyclone structure may help predict their potential for rapid intensification. However, the study also notes that more research is needed to understand how different environmental conditions affect the size of this important inner core.