台风“烟花”的主要特点和路径预报难点分析

对2021年第6号台风“烟花”的主要特点与路径预报重大调整过程中出现的难点问题进行分析和研究,得出主要结论如下。(1)“烟花”移动缓慢,是首个两次登陆浙江的台风,在浙北和杭州湾附近地区长时间滞留。(2)降雨影响范围广、累计降雨量大、大风持续时间长。(3)反映出来的重要难点问题有:当多数模式预报出现一致的偏差时,预报员难以做出订正,有必要开展对模式中台风重要影响系统(高空冷涡、热带对流层上层槽等)的预报检验工作;台风移速缓慢的定量程度难以把握,需要通过总结历史个例和敏感性试验等方法开展东侧台风对西侧台风移动缓慢影响的定量研究;西风带槽/脊对副热带高压退/进快慢的定量影响把握困难,影响北上台风转向点的预报,特别是当不同模式有分歧的时候预报难度更大。

Analysis on main characteristics of Typhoon In-fa and difficulties in its track forecast

In this paper, the main characteristics of the 6th typhoon In-fa in 2021 and the difficulties in the major adjustment process of typhoon track forecast are analyzed and studied. The main conclusions are as follows. (1) Typhoon In-Fa moves slowly and it is the first typhoon to land twice in Zhejiang Province, lingering for a long time near the northern Zhejiang and Hangzhou Bay. (2) The rainfall affects a wide range with large accumulative precipitation and long duration of strong wind. (3) The important and difficult problems reflected are as follows. It is difficult for forecasters to make corrections when there are consistent deviations in most model forecasts. Therefore, it is necessary to carry out the forecast verification work for the systems, such as upper-air cold vortex and tropical upper-tropospheric trough, which have important influence on the typhoon in the models. The slow movement of the typhoon is difficult to quantify, so it is necessary to carry out a quantitative study on the influence of the typhoon in the east on the slow movement of the typhoon in the west by summarizing historical cases and sensitivity tests. It is difficult to quantify the influence of the westerly trough/ridge on the retreat/advance speed of the subtropical high, which affects the forecast of the turning point of northward typhoon, especially when different models have divergent forecasts.