據陶(1980)對衛星雲圖、雷達回波和常規的天氣學資料綜合分析表明：發現颱風中有四種降水類型(1)颱風眼周圍雲牆降水，(2)颱風眼外圍螺旋雲帶降水，(3)颱風和其他系統相互作用產生的降水，(4)與颱風相聯繫的熱帶雲團降水。陳(2002)的研究表明：如果颱風後部西南季風緊跟北上對颱風暴雨的形成有很大作用。本文研究就是西南季風緊跟北上，由低層西南急流引發的暴雨。本文進行了低層流場特徵分析（林，2005）結果表明：颱風登陸後，在其西南側形成了西南急流，閩東北恰好處在西南風急流和東南風急流之間的輻合帶，具有很強的輻合，這是形成閩東北大暴雨的主要原因。本文採用壓能場、水汽通量散度、相對渦度進行動力學分析。壓能場是南京大學氣象系包澄瀾教授研究建立的方法。該研究指出：在低緯度地區及中小尺度分析中，地轉近似不完全適用，甚至不適用，因而改用壓能場分析，據研究暴雨總出現在壓能場梯度最大處。850hPa相對渦度圖顯示，其值達到16×10^(-5)s^(-1)以上有利於暴雨大發生。850hPa水汽通量散度圖顯示：當在水汽通量散度輻合中心，且其值達到-0.8×10^(-6)g•hPa^(-1)•cm^(-2)•s^(-1)或更大時有利於暴雨的發生。此外，地形對颱風暴雨也有一定的增幅作用。

According to Tao (1980): After comprehensive analyzing of satellite images, radar echo, and conventional meteorological data, found that there are four different types of typhoon rainfall: (1) the precipitation from the cloud wall around the typhoon eye, (2) the precipitation from the spiral cloud band outside of the typhoon eye, (3) the precipitation generated by interaction between typhoon and other weather systems, and (4) tropical cloud cluster precipitation related with typhoon. According to Chen Ruishan, if the southwestern monsoon after typhoon come to north closely, the effect on typhoon rainstorm generation is very obvious. The topic of this paper is focus on the torrential rain triggered by southeastern low level jet after the southwestern monsoon move north closely after typhoon. This paper has analyzed the feature of low level air flow field, and the result shows that after typhoon landed, there is southwestern jet at the southwestern side of typhoon, and the convergence between southwestern and southeastern jet is just located in northeastern part of Fujian, the convergence effect is very strong. This is the main reason of heavy rainfall occurred in this region. The paper also studied on the effect of subtropical high on typhoon torrential rain. This paper carried out the dynamic analysis by using pressure energy field data, vapor flux divergence and relative vorticity. The pressure energy field is first adopted by Prof. Bao Chenlan of Meteorological department of Nanjing University. The result shows that: in the meso-and small-scale analysis in low latitude area, the geostrophic approximation is applied imperfect or cannot be applied completely, so need to analyze the pressure energy field, and the conclusion is that heavy rain center is always located in the largest gradient of pressure energy field. The relative vorticity at 850hPa shows that when its value reached 16×10^(-5)s^(-1), it is prone to trigger heavy rainfall. The vapor flux divergence at 850hPa shows that, at the center of the divergence, when the value reached or over -0.8×10^(-6)g•hPa^(-1)•cm^(-2)•s^(-1), torrential rainfall is likely to occur. The paper also analyzed the enhancement effect of topography to heavy rainfall by studying historical data.