Development of a Very Short-Range Forecast of Precipitation System in Vietnam

Precipitation forecast for 1-6 hour is important for disaster prevention to save people’s lives to encourage pre-evacuation, while this time range is a ‘dead zone’ in term of quantitative precipitation forecast. At Vietnam, rainfall analysis is made by composite of ASW, radar and satellite estimation of precipitation with a horizontal resolution of 5km [1]. As development of a very short-range forecast of precipitation system, we tested kinematic extrapolation of rainfall analysis based on lag correlations of hourly rainfall analysis, and merged it with hourly rainfall by a regional NWP model at NCHMF (WRF 3km-DA).

Figure shows a precipitation forecast for 02-07 UTC on 12 September 2021, merging the kinematically extrapolated precipitation from 01 UTC with the 1-hour precipitation forecast by WRF 3km-DA whose initial time is 12 UTC 11 September. The weights of the numerical prediction in the merge were linearly increased from 0 to 1 from 03 UTC to 07 UTC (FT=2 to 6). [2]

References:

[1] Saito, K., M.K. Hung, N.V. Hung, N.Q. Vinh, and D.D. Tien, 2020: Heavy rainfall in central Viet Nam in December 2018 and modification of precipitation analysis at VNMHA. VN. J. Hydrometeorol, 2020(5), 65-79. doi: 10.36335/VNJHM.2020(5).65-79

[1] Saito, K., M.K. Hung, and D.D. Tien, 2023: Development of a very short-range forecast of precipitation system in Vietnam. VN. J. Hydrometeorol. (to be submitted)