目前全球模式对暖区暴雨的捕捉能力有限,北方地区的暖区暴雨预报更是业务预报中的一个难点.2013年7月1-2日河北、天津等地出现了一次区域性大暴雨过程,降水由锋前暖区降水和锋面降水组成,特别是冀中的特大暴雨[409mm· (24h)-1]暖区降水占60％以上.预报员对此次过程的预报量级显著偏小,特大暴雨、暴雨均出现漏报.各家数值模式预报均不能给预报员提供足够的有用信息,给预报带来很多困难,导致预报的失败.本文利用业务预报中常用的数值预报产品、加密自动站观测资料、常规地面、高空观测资料、新一代天气雷达资料等对此次北方暖区暴雨预报失败案例进行剖析,结果显示:高温高湿的环境中,未能捕捉到可触发对流的次天气及以下尺度的小扰动,如地面辐合线、阵风锋、冷池及中尺度涡旋等及其对强降水的影响,加之对中尺度对流系统的环境场条件,如低空急流、急流核的发展演变等的精细分析不足是导致强降水预报量级偏弱的重要因素;对于发生在深厚暖湿气团中的暖区降水的预报,需考虑高温高湿环境下地面辐合线、冷池及中尺度涡旋的相互作用对对流的触发及组织化发展导致的局地性、对流性强降水的产生;基于地面自动站资料和雷达资料等的短时临近预报可以弥补全球数值预报对中小尺度系统的捕捉能力的不足,提高暖区暴雨的预报准确率.%The capacity of global model in forecasting of warm sector heavy rainfall is still very limited at present,especially for warm sector rainfall in northern China,which is one of the most difficult problems in operational forecasting.A severe regional torrential rainfall case which consisted of both warm sector and frontal precipitation attacked Hebei Province and Tianjin during 1-2 July 2013.As for the severe rainstorm [409 mm · (24 h)-1] in the middle part of Hebei Province,the ratio of warm sector rainfall accounted for more than 60 ％ of total precipitation.The heavy rainfall of this event was seriously underestimated in the subjective quantitative precipitation forecast in NMC (National Meteorological Centre) with obvious missing forecast on rainstorm and severe rainstorm.Moreover,none of the numerical weather prediction (NWP) models can provide enough useful information to weather forecasters,which further increased the forecasting difficulty and caused the failure of QPF (quantitative precipitation forecast).In this paper,operational numerical model forecast products,automatic weather station observation,conventional surface and radiosonde observation,and Doppler radar data are employed to investigate the cause of the failure forecast of this warm sector torrential rainfall case.The results show that failure of capturing the sub-synoptic and mesoscale small disturbances,such as surface convergence line,gust front,cold pool,and mesoscale vortex,as well as their effects on heavy rainfall under a high temperature and high humidity conditions was one of the important factors leading to the underestimation of the rainfall intensity.Furthermore,insufficient fine analysis on the environment condition in triggering mesoscale convection systems like low-level jet and the evolution of jet core also played important roles.Therefore,in terms of forecasting the warm sector rainfall within a very thick warm wet air mass,the triggering caused by interaction of surface convergence line,cold pool and mesoscale vortex and organizational development of local and convective precipitation in the high temperature and high humidity environment must be considered.Short-time forecast and nowcasting based on surface automatic weather station observation and weather radar data could effectively compensate the lack of ability in finding mesoscale and small-scale systems by global NWP models,which may improve the accuracy of forecasting warm sector rainfalls.
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