萍乡地区两次暴雨前夕预报诊断分析

Forecast Diagnosis on the eve of twice heavy rains in Pingxiang

利用常规天气图、WRF数值模式等资料,对萍乡地区2010年5月两次暴雨前夕主要影响天气系统的演变进行分析,结果表明:中低层切变线和低涡、地面西南倒槽、副热带高压是这两次大暴雨过程的主要影响天气系统,地面西南倒槽的发展加强和副热带高压的北抬,为这两次暴雨的产生起到了不可忽略的作用;暴雨发生前夕,高空急流和中低层强盛西南气流是动力触发条件;暴雨落区上空低层高能舌加强延伸是热力触发条件;两次大暴雨过程产生的天气背景很相似,但影响系统的位置和强度有所差异;WRF降水落区预报和降水量级预报基本符合实况降水,但是降水预报量级偏小,与实况降水稍有出入,在天气预报业务中有较好辅助作用和参考价值。

By means of conventional weather charts, WRF numerical model and other data, the evolution of major affected weather systems on the eve of twice heavy rains in Pingxiang on May 2010 is analysed. The results show that：the middle-low level shear line vortex, the ground southwest-inverted trough,and the subtropical high are the major affected weather systems in the two processes of large rain storms,the enhancement and development of ground southwest-inverted trough and the northward move of subtropical high play an important role in the production of the twice heavy rains;on the eve of heavy rains,high-altitude jet stream and strong low-level southwesterly flow are dynamic triggering conditions,and the strengthening and extending northeast of low-level high energy tongue over heavy rain area is thermal triggering conditions;the weather processes of two large rain storms are very similar in background, but the impact of location and intensity of the systems is different;the forecast of WRF rainfall region and rainfall magnitude is basically consistent with reality, but the order of magnitude is smaller and a little bias than precipitation forecast, but WRF model has a good supporting role and provides references in the weather business.