Study on Hail Probability Forecast Method Based on Objective Classification

Abstract

Based on NCEP （National Centers for Environmental Prediction） GFS （Global Forecast System） data， the weather situation was classified and the environmental parameters were analyzed by using 54 large hail samples from 25 hail weather processes in Hubei Province during 2004 -2015.Based on the percentile statistical characteristics of environmental parameters， by selecting the ascending and descending half ridge functions， the continuous probability method is used to establish the probability prediction models of hail occurrence in weather situation of front trough and behind the trough.The hail occurrence probability in weather situation of easterly flow type is calculated by dichotomy.In the practical forecast， ECMWF（European Centre for Medium-Range Weather Forecasts）numerical forecast model is used to carry out the hail probability forecast based on objective classification of three types of weather situation， and real-time forecasting is carried out during 2017 -2020.The evaluation results of four typical hail processes in three types of weather situation show that the hail forecast effect is good.Taking 60% probability as the critical threshold for hail prediction， the POD （probability of detection） is 91.2%， the MR （missing rate） is 8.8%， the FAR （false alarm rate） is 51.5%， and the TS （threat score） is 46.3%， The forecast time advance can be from 12 to 24 hours.

Keywords

• objective classification
• hail
• probability forecast