一场局地强天气征兆分析

An Analysis of Local Severe Weather Signs

2016年4月23日,受南支槽东移、中低层切变线南压以及低层SW急流等共同影响,福建省仙游县部分乡镇出现了暴雨、局部大暴雨。其中,湖洋当日降水量最大,达108.4 mm,最大雨强达48.0 mm/h。此次局地暴雨时空分布零散,主要出现在西部、北部高海拔山区,地形增幅作用明显。局部强对流天气造成局地洪涝、泥石流等地质灾害。短时强降水发生前的4月23日08:00,低层低涡切变线东移南压,其南侧925~700 HpaSW急流开始建立,仙游县位于急流附近,500 Hpa南支槽加深东移靠近,槽前SW气流持续增强。200 hpa有较强的辐散流场,抽吸作用非常明显,使得低层气流不断猛烈地抬升,大气层结非常不稳定。根据高低空流场、自动站观测以及天气雷达监测资料,结合当时各种物理参数的变化等,对2016年4月23日仙游县局地强对流天气出现前的征兆进行分析,以便为今后局地强对流天气预报提供借鉴。

On April 23,2016,affected by the eastward movement of the south branch trough,the south pressure of the shear line in the middle and low levels and the SW jet in the low level,some townships in our county had a heavy rain,and some local heavy rain.Among them,the precipitation of 108.4 mm in Huyang was the largest,and the heaviest rain intensity was 48.0 mm/h.The spatial and temporal distribution of the local rainstorm is scattered,mainly in the western and northern high-altitude mountain areas,and the effect of terrain increase is obvious.Local strong convective weather caused local flood,debris flow and other geological disasters.At 08:00 o’clock on April 23,before the short-time heavy precipitation,the vortex shear line at the lower level moved eastward and pressed southward,and the jet stream of 925~700 HpaSW on its south side began to establish.Our county is near the jet stream,the 500 hPa south branch trough deepened and moved eastward and approached,and the SW airflow in front of the trough continued to strengthen.At 200 hPa,there is a strong divergent flow field,and the pumping effect is very obvious,which makes the low-level airflow constantly violently uplifted,and the atmospheric junction is very unstable.According to the high and low space flow field,automatic station observation and weather radar monitoring data,combined with the changes of various physical parameters at that time,the symptoms before the occurrence of local strong convective weather in Xianyou County on April 23,2016 were diagnosed and analyzed,so as to provide some reference for the future forecast of such local strong convective weather.