阿勒泰地区一次暴雨预报难点分析

Forecast Difficulties Analysis for a Rainstorm in Aletai Area

摘要: 2011年7月21日午后至傍晚，阿勒泰地区自西向东出现不同程度的降水，福海、富蕴、青河站出现暴雨，其它站为小雨。本文利用2011年7月21日阿勒泰地区降水资料、EC、高空实况、卫星云图及T639产品对此次突发性暴雨进行诊断分析。结果表明，此次天气的主导系统欧洲长脊，影响系统是东移北上的中亚低槽。影响此次天气的中尺度系统是850 hPa切变线及中尺度对流云团。并通过21日08时高空实况要素场分析，此次天气触发机制主要变现在四方面，分别为大气层结不稳定、低空偏东急流、“抽气效应”及地形作用。但是T639数值预报产品在此次天气预报中，预报能力差，水汽条件及动力条件均不支持阿勒泰地区南部、东部的暴雨，体现了数值模式预报对中小尺度系统预报能力的欠缺。

Abstract: There appeared different degree of precipitation in Aletai from West to East in the afternoon of July 21, 2011, and it happened rainstorm in Fuhai, Fuyun, Qinggil station, other stations for rain. By analysing the data of precipitation, EC, high live, satellite images and T639 in Aletai on July 21, 2011, the results showed that the dominant system was the long ridge in Europe, and its influence system was the eastward and northward moving low trough in central Asia. The mesoscale system influencing the weather is 850 hPa shear lines and mesoscale convective cloud. By analysing the high-altitude live elements field 21 at eight o’clock, the weather triggering mechanism is mainly manifested in four aspects: the unsteady stratified atmosphere, an east lower troposphere jet, "pumping effect” and the effect of terrain. The forecast ability of T639 numerical forecast products is poor in the weather forecast, and the water vapor condition and dynamic condition all do not support the rainstorms in southern and eastern Aletai. It reflects the lack of prediction model on the prediction ability of small and medium scale system.