201211号台风“海葵”近海路径和强度突然变化的成因分析

Study on the cause of the sudden change in the path and strength of typhoon “Haikui”

运用天气学和动力诊断方法,结合卫星云图,分析了1211号台风"海葵"在浙江近海移向突然变化、强度爆发性增强的原因。结果发现:大陆暖高东移过程中脊线的转变,西太平洋副高西伸加强北抬,并与大陆暖高合并是促使"海葵"移向转变、移速加快的关键因素。"海葵"进入浙江近海时,弱的环境风垂直切变、强烈的低层辐合和高层辐散、东风急流和西南气流水汽输送的加强、低层正涡度的输入是其得以爆发性增强的主要原因。台风爆发性增强时,卫星云图上表现为:台风环流螺旋度迅速加大,结构密实,有完整清晰的台风眼形成,眼区范围缩小,南北两条水汽输送通道建立,水汽输入云带发展强烈,以及台风水平尺度发展到最大等特征。

Using the synoptic analysis and dynamic diagnosis method, combined with the satellite image, the reason of the sudden change in direction and explosive intensification of“Haikui”offshore Zhejiang is analyzed. It is found that the transformation of the continental warm high ridge line during the eastern shift, reinforcing of the western Pacific subtropical high and its merger with continental warm high, are the key factors resulting in the direction change and speed up of“Haikui”. When“Haikui”entered Zhejiang offshore sea, the weak environment vertical wind shear, strong low-level convergence and high-level divergence, strengthening of water vapor transmission by easterly jet and southwest airflow, lower level positive vorticity input, were the main reasons for its explosive intensification. During the time of“Haikui”explosive intensification, the satellite images showed that the helicity of typhoon circulation was rapidly increasing, and the typhoon structure was dense and full with a complete clear typhoon eye formation and narrowing of the eye area. The two water vapor transmission channels were established in the north and south, the inputting water vapor cloud bands developed strongly, and the horizontal scale of the typhoon reached its maximum range.