Dự báo lại đợt dông gây mưa đá ngày 24–25/01/2020 trên khu vực Đông Bắc Bộ bằng mô hình số

Abstract

In this study, the WRF-ARW model was used to reforecast thunderstorminduced severe hail in eastern North Vietnam in 24-25/01/2020. The results show that the model was able to reproduce the large-scale patterns favorable for the storm development, that is, low-level convergence in compressed trough, cold front, and associated upper-level trough and jet. Convergence of southerly vertically-integrated moisture fluxes helps to energize hailstorms. Computed hailstorm indexes, including Updraft Helicity (UH) and Column integrated Total Graupel (CTG), indicate that the model could well predict locations, timing, and propagation directions of hailstorms. In terms of magnitude, the UH index exceeds but CTG belows the threshold of severe hail (equivalent to maximum hail size > 25 mm in diameter). The vertical distribution of graupel suggests that indexes used in NWP to predict hailstorms, which were determined for those in the extratropics in summer, could be adjusted to be more suitable for hailstorms happening in Vietnam in winter or transition months.