Mechanism influencing forecast errors of the nearshore track of super typhoon Lekima (1909)

Although significant progress has been made in numerical forecasting of typhoon tracks and intensity, meeting the needs of operational forecasting remains challenging. Based on the high-resolution Weather Research and Forecasting (WRF) model, eight sets of combination experiments are conducted with different model initial conditions, initialization times, and microphysical parameterization schemes. The results indicate that model initial conditions exhibit the highest sensitivity in forecasting the track of typhoon Lekima (1909). Representative experiments are selected based on track errors, and sensitivity experiment is conducted to further explore the mechanisms responsible for significant differences in typhoon track forecasts arising from different model initial conditions. The results indicate that the accurate forecasting of the strength and extent of the Western North Pacific subtropical high (SH) plays a crucial role in determining the quality of typhoon track predictions. An overestimation of the SH in the initial field leads to the stronger predicted SH, results in westward movement of the typhoon being blocked along the SH and its northward progression slowed. This leads to significant errors in track forecasting of typhoon. Additionally, the forecast errors in the typhoon’s inner core structure at different stages are related to the predicted typhoon track. The vertical wind shear in the large-scale circulation field may be a significant factor contributing to this error. Moreover, an overestimation of the SH’s extent and intensity leads to deeper asymmetric distribution of horizontal wind speeds near the typhoon, which contributes to the occurrence and development of deep convection. This is an important reason for the slower moving speed of the typhoon.