Testing the Performance of Dynamical Initialization for the Rapidly Intensified Tropical Cyclones in the Western North Pacific

The rapid intensification (RI) is an interesting scientific issue and enigmatic problem in tropical cyclone (TC) intensity forecast. Although the number of RI is only a small percentage of the total TC number, it frequently causes large intensity forecast errors in terms of the central pressure and maximum sustained wind. To tackle this RI issue, we have developed a dynamical initialization (DI) method combined with the high-order filter equations, which can decompose the field into large-scale and vortex-scale fields. During the cycle-run stage, the large-scale field is preserved as consistent with the global data, but the vortex-scale field is continually updated until they reach to best track intensity.

In the present study, the RI is defined as when the maximum surface wind increases by 30 kt and minimum central sea-level pressure decreases by 42 hPa within 24 h. For the better credibility of DI method, we have selected quite a number of RI cases from 2013 to 2016 in the western North Pacific, and each RI case is initialized with 12 h intervals by using DI from the genesis to dissipation. Based on the results of all RI cases, we have comprehensively analyzed the general characteristics on RI such as the impact of vertical wind shear, convective bursts, and warm-core structure. We think that the better initialization could improve the early prediction of RI by more than 24 h lead time.