Climatology and Nowcasting Methods for Thunderstorm Gale in Beijing
Right now, the warning accuracy of the high wind is lower and the lead ing time is also very limited in Beijing. In order to change the situation, the forecasting methods are developed. Based on the statistics for 134 cases, it is known that most of the high wind events are caused by the downbursts and some of them break out while the hails are falling. Therefore, the negative buoyancy an d the hail storm factors should be taken into consideration in study of this sev ere weather. Even though most of the high winds break out when the air at the middl e level becomes drier, there are still a few of events appearing in the warm and wet flow. The mechanism for the latter one is not clear yet. When there is some dryincursion in the middle level of troposphere, the favorable conditions for the h igh wind are the great instability in ambient for downdraft and higher temperatu re lapse rate in the lower level. Besides, the use of WINDEX is also discussed. The potential forecasting method is developed on the basis of above study. Furth ermore, the nowcasting equation on the basis of the radar reflectivity, radial s peed a nd so on as the forecasting factors is given through the correlation analysis an d multiple regression analysis. The case study shows that some strong wind gusts caused by squallline or bow echo could be forecasted successfully by using th e equation.