一次副高控制中局部大暴雨预报失误原因分析

摘要

[目的]研究一次副高控制中局部大暴雨预报失误的原因.[方法]从总结预报失误的原因出发,利用常规的地面观测资料、高空探测资料、T639和T213以及欧洲中心(ECMWF)数值预报产品资料、美国国家环境预报中心的GFS降水预报产品,对2010年8月5日发生在邵阳北部一次大暴雨过程发生前后的天气形势、物理量场进行了细致分析;利用数值分析预报产品资料,采取预报与实况对比分析方法,对这次副热带高压中大暴雨预报失误的原因进行了较全面深入的分析.[结果]预报人员对天气形势分析不够深入细致,表面上500 hPa为副高控制,但实际上700和850 hPa存在弱的切变线,并忽视了弱冷空气和东风波的影响;副高迅速减弱,系统调整过快,ECMWF预报850、700和500 hPa风场变化与实况存在较大误差,比实况偏东2个经度左右;在夏季预报中仅考虑500 hPa副高强度和位置变化,忽视了中低层和地面形势的变化,是导致这次副高中暴雨预报失败的最关键因素;数值预报产品对高度场形势变化的预报误差较大,日本FSAS降水预报、美国国家环境预报中心的GFS预报和T639、T213降水预报都偏小,T639湿度场预报值较小;在此次暴雨预报中,没有当地暴雨预报指标方法用于预报实践;在降水预报过程中只注重该站点的评分预报,对非站点预报不够重视,有些重要的物理量因素没有能仔细推敲.[结论]该研究为此类局地大暴雨的预报预警提供参考依据.%[ Objective ] The research aimed to study the reason of local heavy rainstorm forecast error in the subtropical high control. [ Method] Started from summarizing the reason of forecast error, by using the conventional ground observation data, the upper air sounding data,T639, T213 and European center (ECMWF) numerical prediction products data, GFS precipitation forecast product of U. S. National Center for Environmental Prediction, the weather situation, physical quantity field in a heavy rainstorm process which happened in the north of Shaoyang at night on August 5, 2010 were fully analyzed. Based on the numerical analysis forecast product data, the reason of heavy rainstorm forecast error in the subtropical high was comprehensively analyzed by using the comparison and analysis method of forecast and actual situation.[ Result] The forecasters didn't deeply analyze the weather situation. On the surface, 500 hPa was controlled by the subtropical high, but there was the weak shear line in 700 and 850 hPa. Moreover, they neglected the influences of weak cold air and easterly wave. The subtropical high quickly weakened, and the system adjustment was too quick. The wind field variation in 850,700 and 500 hPa which was forecasted by ECMWF had the big error with the actual situation and was by east 2 longitudes than the actual situation. In summer forecast, they only considered the intensity and position variation of 500 hPa subtropical high, neglected the middle, low levels and ground situation variations. It was the most key element which caused the rainstorm forecast error in the subtropical high. The forecast error of numerical forecast products on the height field situation variation was big. The precipitation forecasts of Japan FSAS, U.S. National Center for Environmental Prediction GFS, T639 and T213 were all too small. The humidity field forecast value of T639 was small. In the rainstorm forecast, the local rainstorm forecast index method wasn't used in the forecast practice. In the precipitation forecast process, they only paid attention to the score prediction of station and didn't value the non-site prediction. Some important physical quantity factors weren't carefully elaborated. [ Conclusion] The research provided the reference basis for the forecast and early-warning of local heavy rainstorm.