登陆北上台风突然转向的预报着眼点

以2018年两个登陆北上影响山东的台风"摩羯"和"温比亚"为例,讨论分析了深入内陆的台风在突然转向时刻的预报着眼点。结果表明:台风的移动路径很大程度上取决于副热带高压(大陆高压)的位置与强度,当高压偏强时,可由三力平衡原理确定台风未来的移动方向。同时,300~200 hPa高度层的风向可以提前18 h指示台风即将发生路径偏折。15日08时,台风"摩羯"转向角较大,主要原因是受高频引导气流影响,且沿着正高频涡度平流的方向移动。而"温比亚"进入渤海向东北方向移动,是受全风速与低频气流影响。这表明高频流对转向角度较大的台风起引导作用,而环境风场对转向角度不大的台风起作用。

Forecasting factors of the northward sharp turn of typhoons that make landfall

The key forecasting factors of typhoon’s sharp turn are discussed and analyzed by taking typhoon YAJI and RUMBIA as examples, which made landfall and affected Shandong province in 2018. The results show that the typhoon track largely depends on the location and intensity of the subtropical high(continental high). The typhoon direction can be predicted using the principle of three forces balance when the subtropical high is more significant. Meanwhile, the wind direction of the 300~200 hPa level can be used to predict the change of typhoon direction 18 hours in advance. The sharp turn of typhoon YAJI at 08: 00 on August 15 is due to the influence of high-frequency airflow and its movement along the positive high-frequency vorticity advection. The full wind speed and low-frequency airflow lead typhoon RUMBIA turn to the northeastward when it enters Bohai Sea. It can be concluded that high-frequency advection favors the sharp turn of typhoon direction, while the environmental wind field influences the typhoon with subtle change in direction.