重庆“8.22”暴雨ECMWF模式中期预报转折分析

Analysis on ECMWF Model Medium-Term Forecast Transition of“8.22”Heavy Rainfall Process in Chongqing

2018年8月22-23日重庆中部地区一次暴雨过程的预报出现了明显的偏差,本研究利用降水实测资料、高空探测资料和ECMWF(以下简称EC)模式的形势预报对降水产生原因、影响系统以及EC模式不同起报时间的预报效果进行了分析,结果表明:(1)此次暴雨过程是在高空槽和中低层切变线的共同影响下产生的.(2)EC模式降水预报在8月19日前后出现了突变,其原因是影响重庆地区的500 hPa高度场发生了转折性的变化.(3)在500 hPa高度场预报与实况基本一致的情况下,重庆中部地区的中低层切变线是20日主观预报降水落区与实况出现明显误差的原因.

There was a significant deviation in the forecast of the heavy rainfall process in central Chongqing from August 22 to 23,2018.The precipitation observation data,high-altitude detection data and the synoptic situation forecasts from the ECMWF model(hereinafter referred to as EC)have been used in this paper to analyse the cause and influencing weather system of this process.The effects of different reporting time from the EC model were also evaluated.The results show that 1)This rainstorm process was under the joint influences of the high-altitude trough and the middle-lower level shear line.2)The precipitation forecasts from the EC model had a sudden change around July 19,which was caused by the transitional change of the 500 hPa geopotential height field forecasts from the same model in Chongqing.3)Under the condition that the 500 hPa height field forecasts was basically consistent with the actual situation,the middle and lower layer shear line in the central part of Chongqing was the reason for the apparent deviation between the subjective precipitation forecast in August 20 and the actual rainfall distribution.