Upper Bound on Hurricane Intensity Forecast Errors

In this study, the growth of hurricane intensity errors at the maximum potential intensity (MPI) limit will be examined in a phase space of hurricane basic scales, using an axisymmetric hurricane model. It will be shown that there exists an MPI attractor at the maximum intensity limit that all hurricane orbits will converge into, regardless of hurricane initial conditions. Direct estimation of the leading Lyapunov exponent shows that the MPI attractor is not only an attracting set but also chaotic in nature. This finding of the chaotic MPI attractor suggests an upper bound on the predictability limit of the hurricane intensity, which prevents the 4-5 day absolute intensity errors in hurricane model forecasts from being reduced below a threshold of ~8-10 m s-1.