Practical Predictability of Tropical Cyclone Intensity

Abstract:

This study examines the practical predictability of the tropical cyclone (TC) intensity. Analyses of flow orbits in an axisymmetric TC model reveal existence of a dense and bounded attractor for the maximum potential intensity (MPI) in the phase space of the TC scales, which is determined more by the large-scale environmental condition. Direct estimation of the leading Lyapunov exponent in the axisymmetric model shows further that the attractor is not simply an attractive set but is chaotic in nature. This result suggests that future improvement of TC longer-range intensity forecasts will be more realized as a result of the large-scale improvement rather than improvement in the TC initial condition. In particular, finding of the MPI chaotic attractor provides direct implication about the limited predictability of the TC intensity, which prevents the intensity errors at the mature stage from being reduced below an estimated threshold of ~ 8 m s^-1.