一次副高控制下登陆的台风强降雨过程分析

Analyses of a strong precipitation event by the landing typhoon under the control of subtropical high

1521号台风"杜鹃"是在5 880 gpm副高控制下,5 920 gpm副高加强西伸过程中,登陆福建莆田沿海的。分析发现副高的加强西伸和低空华北高压的东移,改变了"杜鹃"东部低空急流和水汽辐合的分布,导致水汽辐合和不稳定能量在浙闽东部汇聚,在高空幅散、低空辐合产生的强烈上升运动触发下,产生大暴雨和特大暴雨。"杜鹃"消亡后,925 h Pa以下的边界层残留低压倒槽顶部东南急流与偏东急流的汇合,使水汽辐合和不稳定能量在浙北东部持续,是该地区继续出现大暴雨的主要原因。"杜鹃"外围东南急流与偏东急流的汇合造成的降雨回波,结构虽没那么致密,但发展更为旺盛,对流性更强,更易造成特强降水,业务预报中,需特别引起注意。

Analyses results show that the strengthening and western extension of subtropical high and the eastern extension of low level North China high changed the vapor transportation and distribution of low level jets and vapor convergence of 1521 Typhoon ＂Dujuan＂. Strong vapor convergence and unstable energy accumulated in the eastern parts of Zhejiang and Fujian provinces with the strong ascending motion resulted by the coupling of high level divergence and low level convergence, which caused extraordinary torrential rain. After the withering away of ＂Dujuan＂, the low southeastern jet and east jet of its residual low pressure inverted trough top met at the eastern part of north Zhejiang province, which resulted in the continuity of vapor convergence and unstable energy and caused the continuity of extraordinary torrential rain. The meeting of the southeastern jet and east jet of peripheral ＂Dujuan＂ caused strong rainfall echo, whose structure is not so compact, but more convective and more likely to cause extraordinary strong precipitation, which should be paid attention to operational forecast in future.