2015年7月31日夜间,太行山区出现极端短时强降水天气,石家庄和邢台的西部山区有5个雨量站雨量超过100 mm,其中石家庄市赞皇县院头镇和邢台市临城县南中皋村最大雨强都超过50 mm·h-1,3h雨量超过100 mm,属极端短时强降水.数值预报、上级指导预报以及各级台站预报对暴雨均为漏报.本文利用常规高空地面观测资料、加密自动站观测资料、石家庄新一代天气雷达资料以及数值预报检验,反思该极端短时强降水预报思路和预报失败原因.此次极端短时强降水是发生在青藏高压东北侧高空西北气流的弱天气尺度背景下,预报的关键在于把握太行山东侧边界层偏东风与地形的作用、青藏高压加强使中层西北气流加强使垂直风切变加大、低层切变线东移影响、西南暖湿气流增强使水汽输送增加、中空干层与加厚的低空湿层叠加使对流不稳定性加强的特征.预报失误的主要原因是没有分析最大不稳定能量(订正CAPE值)导致对山西不稳定条件的低估,致使对山西雷暴在夜间的再次发展估计不足,同时预报员没能有效地使用非常规资料用于实时检验和订正数值预报结果,导致没能预见到雷暴下山增强的可能.目前对弱天气背景下强降水产生条件缺乏有效的概念模型,数值模式可预报性较差,未来需要提高预报员对观测资料的全面分析能力和对数值预报产品的释用能力,通过大量个例的研究发展有效的预报(概念)模型.%In midnight on 31 July 2015,an extreme flash-rain event was happened in Taihang Mountain.The rainfall was more than 100 mm at 5 automatic weather stations (AWSs) in mountain areas of Shijiazhuang and Xingtai,of which Yuantou town of Shijiazhuang City and Nanzhonggao Town of Xingtai City were caught by extreme short-time intense rainfall with rainfall amount more than 50 mm · h-1 and more than 100 mm · (3 h)-1.However,the numerical prediction,the superior guidance forecast and meteorological observatory all failed to forecast this rainstorm.Based on conventional upper-level and surface observations,AWS data,Doppler weather radar data and numerical forecast test,this paper analyzed the prediction ideas and the reason of failure.The event occurred under weak synoptic-scale background in northeast of Tibetan high.The key of forecasting severe precipitation was to grasp the effects of east wind in Taihang Mountain and terrain.The middle-level northwest flow strengthened vertical wind shear,lowlevel shear line moved eastward,southwest wind strengthened warm moist air flows,and dry air layer overlaid on the thicken wet layer,strengthening the convective instability.The primary reason of the forecast error is that the lack of analyzing the maximum CAPE led to underestimating the unstable conditions and the development of thunderstorm at night in Shanxi Province.In addition,forecasters failed to use the unconventional data for real-time testing and correct numerical results,thus failing to predict the enhancement of thunderstorm enhance when it went down the hill.There is no effective conceptual model for severe precipitation conditions in the weak weather background at present.Forecast capacity of numerical model for such weather is poor.So forecasters need to improve the comprehensive analysis ability on observational data and the interpretation capacity of numerical prediction products in the future,and also to develop effective forecasting conceptual model through studying a large number of cases.
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