An Ingredients-Based Methodology For Forecasting Rainstorm In The Low Reach Of Yangtze River

The concept and research progress of ingredients-based methodology is introduced, and further more is applied in Nantong. An ingredients-based methodology (IM) is an interpretation of numerical models products to forecast rainstorm and severe weather, thinking that heavy precipitation is the causation of ingredients. A parameter ZH, which serves as an indicator of heavy precipitation potential, is designed, in order to fix point and to fix quantity. A warning platform system for NanTong is built up.An ingredient is defined as a fundamental physical element or process that directly contributes to the development and intensity of a precipitation event. The accurate combination of basic ingredients can produce intending weather phenomenon. The basic factors for rainstorm are ascending, instability, moisture and precipitation efficiency etc.According to these principles, the Q vector convergence is employed to qualitatively assess QG forcing for ascent, saturated geostrophic equialent potential vorticity is used to identify regions of instability , relative humidity and depression of dew point are used to qualitatively assess moisture and precipitation efficiency. According to the historical data of 1998-2003, the relationship between ZH and precipitation is obtained. And then the precipitation area and intensity may be determined.This paper gets some basic conclusions: index ZH is better than signal physical parameter;index ZH is good at forecasting rainstorm;the index of area average of 8 stations around NanTong is better than at NanTong. At the same time, the visualization interface is designed to facility forecasters.