Abstract
The ability of numerical simulations to predict typhoons has been improved in recent decades. Although the track prediction is satisfactory, the intensity prediction is still far from adequate. Vortex initialization is an efficient method to improve the estimations of the initial conditions for typhoon forecasting. In this paper, a new vortex initialization scheme is developed and evaluated. The scheme requires only observational data of the radius of maximum wind and the max wind speed in addition to the global analysis data. This scheme can also satisfy the vortex boundary conditions, which means that the vortex is continuously merged into the background environment. The scheme has a low computational cost and has the flexibility to adjust the vortex structure. It was evaluated with 3 metrics: track, center sea-level pressure (CSLP), and maximum surface wind speed (MWSP). Simulations were conducted using the WRF-ARW numerical weather prediction model. Super and severe typhoon cases with insufficiently strong initial MWSP were simulated without and with the vortex initialization scheme. The simulation results were compared with the 6-hourly observational data from Hong Kong Observatory (HKO). The vortex initialization scheme improved the intensity (CSLP and MWSP) prediction results. The scheme was also compared with other initialization methods and schemes.
Highlights
To reduce the damage caused by tropical cyclones (TC), it is very important to predict their track and intensity correctly
As mentioned by Marks et al [3], the primary reason for the slow progress in improvement of intensity prediction is that the intensity depends on the inner-core dynamics, whereas the track prediction depends more on the large-scale environments
It has been suggested that the accurate representation of the inner-core structure of tropical cyclones in the initial conditions is as important as the representation of the largescale environment [4]
Summary
To reduce the damage caused by tropical cyclones (TC), it is very important to predict their track and intensity correctly. Track prediction has been steadily improved [1]. There has been little improvement in predicting the intensity of typhoons [1]. As mentioned by Marks et al [3], the primary reason for the slow progress in improvement of intensity prediction is that the intensity depends on the inner-core dynamics, whereas the track prediction depends more on the large-scale environments. The inner-core dynamics are mainly associated with vortex structure, intensity, and vortex size. It has been suggested that the accurate representation of the inner-core structure of tropical cyclones in the initial conditions is as important as the representation of the largescale environment [4]. For the super typhoon Genevieve (2014) at 12:00 (UTC) on 9 Aug 2014, the center sea-level pressure (CSLP) derived from FNL (NCEP final analyses) data is around 993 hPa, whereas the observational CSLP from HKO is 940 hPa
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