Mai Van Khiem, Woo Wang-chun, Wong Wai-kin, Yeung Siu Lun, Du Duc Tien, Mai Khanh Hung, Dang Dinh Quan, Pham Thi Phuong Dung, Nguyen Thi Nga, Chu Thi Huyen Trang

Main Article Content


In the very short-range forecast (less than 12 hours) of heavy rain and severe thunderstorms, the main challenge is primarily on tracking and predictingng of growth and decay of significant convective systems. With the advances in nowcasting techniques, analysis and nowcasting of heavy rain and thunderstorm from radars and satellites have been improving progressively. The intensity changes of convective weather from direct output of numerical weather prediction (NWP) models would contain substantial errors due to data assimilation and spin-up issues of model physical processes. In this paper, we would introduce a new blending system being implemented in NCHMF to enhance nowcasting and forecasting services. The system includes: i) extrapolations of rain/convective systems of Vietnam’s radar mosaic (or single radars) for first 1-6 hours based on radar based on the Short-range Warning of Intense Rainstorms in Localized Systems (SWIRLS) developed by the Hong Kong Observatory (HKO), and ii) a rapidly update convective-permitting NWP system based on WRF-ARW in the convective scale to provide the forecast up to the next 12 hours. Firstly, 1-6 hours forecast from models are calibrated with radar-based quantitative precipitation estimates and nowcasts. The study will present some initial results of the blending system and discuss verification of the quantitative precipitation forecast.


Keywords: SWIRLS; nowcasting; radar extrapolation; high resolution numerical weather prediction.


[1] K. Stephan, S. Klink, C. Schraff, Assimilation of Radar-Derived Rain Rates into the Convective-Scale Model COSMO-DE at DWD, Quarterly Journal of the Royal Meteorological Society, 134, 2008, pp. 1315–1326,
[2] A. Walser, D. Lüthi, C. Schär, Predictability of Precipitation in a Cloud-Resolving Model, Monthly Weather Review, Vol. 132, 2004, pp. 560-577,;2.
[3] L. Cuo, T. C. Pagano, Q. J. Wang, A Review of Quantitative Precipitation Forecasts and Their Use in Short- to Medium-Range Streamflow Forecasting, Journal of Hydrometeorology, Vol. 12, 2011, pp. 713-728,
[4] W. K. Wong, L. Yeung, Y. C. Wang, M. X. Chen, Towards The Blending of NWP with Nowcast: Operation Experience in B08FDP World Weather Research Program Symposium on Nowcasting, Whistler, BC, Canada, 2009.
[5] G. Wang, W. K Wong, Y. Hong, L. Liu, J. Dong, M. Xue, Improvement of Forecast Skill for Severe Weather by Merging Radar-Based Extrapolation and Storm-Scale NWP Corrected Forecast, Atmospheric Research, Vol 154, 2015, pp. 14-24,
[6] X. Li, J. R. Mecikalski, Assimilation of The Dual-Polarization Doppler Radar Data for a Convective Storm with a Warm-Rain Radar Forward Operator. Journal of Geophysical Research: Atmospheres, Vol. 115, 2010,
[7] M. Lindskog, K. Salonen, H. Järvinen, D. B. Michelson, Doppler Radar Wind Data Assimilation with HIRLAM 3DVAR. Monthly Weather Review, Vol. 132, 2004, pp. 1081-1092, 0493(2004)132<1081:DRWDAW>2.0.CO;2.
[8] M. Dixon, G. Wiener, TITAN: Thunderstorm Identification, Tracking, Analysis, and Nowcasting-A Radar-based Methodology, Joủnal of Atmospheric and Oceanic Technology, Vol. 10, 1993, pp. 785-797,<0785:TTITAA>2.0.CO;2.
[9] A. Bellon, I. Zawadzki, A. Kilambi et al., McGill Algorithm for Precipitation Nowcasting by Lagrangian Extrapolation (MAPLE) Applied to the South Korean Radar Network. Part I: Sensitivity Studies of the Variational Echo Tracking (VET) Technique, Asia-Pacific Journal of Atmospheric Sciences, Vol. 46, 2010, pp. 369-381,
[10] B. J. Turner, I. Zawadzki, U. Germann, Predictability of Precipitation from Continental Radar Images. Part III: Operational Nowcasting Implementation (MAPLE), Journal of Applied Meteorology and Climatology, Vol. 43, 2004, pp. 231-248,;2.
[11] M. C. Wong, E. S. T. Lai, P. W. Li, Applications of Nowcasting Products to Real-time Warning
of Hazardous Weather in Hong Kong, WMO PWS Workshop on Warnings of Real-time Hazards
by Using Nowcasting Technology, Sydney, Australia, 2006.
[12] N. H. Dien, Empirical Formulas for Calculating Rainrate from Radar Reflectivity for the Mid-Central Vietnam. VNU Journal of Science: Natural Sciences and Technology, Vol. 25, No. 3S, 2009, pp. 390-396 (in Vietnamese).
[13] J. Sun, N. A. Crook, Dynamical and Microphysical Retrieval from Doppler Radar Observations Using a Cloud Model and Its Adjoint. Part I: Model Development and Simulated Data Experiments, Journal of the Atmospheric Sciences, Vol. 54, 1997, pp. 1642-1661,;2.
[14] J. Michalakes, J. Dudhia, D. Gill, T. Henderson, J. Klemp, W. Skamarock, W. Wang, The Weather Research and Forecast Model: Software Architecture and Performance, Proceedings of the Eleventh ECMWF Workshop on the Use of High-Performance Computing in Meteorology, World Scientific, 2005, pp. 156-168,
[15] W. C. Skamarock, J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, M. G. Duda, X. Y. Huang, W. Wang, J. G. Powers, A Description of the Advanced Research WRF Version 3, University Corporation for Atmospheric Research, 2008,
[16] D. D. Tien, B. M. Tang, V. V. Hoa, P. T. Vui, T. A. Duc, N. T. Tung, Assimilating Dong Ha Radar to Improve the Quality of Heavy Rainfall Forecast Over the Middle Vietnam, Vietnam Journal of Hydrometeorology, No. 632, 2013, pp. 12-19 (in Vietnamese).
[17] K. Q. Chanh, Overview of the Ensemble Kalman Filter and Its Application to the Weather Research and Forecasting (WRF) Model, VNU Journal of Science: Natural Sciences and Technology, No. 1S, pp. 17-28 (in Vietnamese).
[18] V. V. Hoa, Skill Validations of Tropical Cyclone Track Forecast of the WRF Model, Vietnam Journal of Hydrometeorology, No. 3, 2008, pp. 37-46 (in Vietnamese).
[19] T. T. Tien, C. Thanh, N. T. Phuong, Forecasting Hurricane Intensity Over on Eastern Sea of Viet Nam Using WRF Model for 5-day Term, VNU Journal of Science: Natural Sciences and Technology, Vol. 28, No. 3S, 2012, pp. 155-160 (in Vietnamese).
[20] D. J. Yik, Y. W. Sang, N. K. Chang, F. J. Fakaruddin, A. Dindang, M. H. Abdullah, Analysis of the Cyclonic Vortex and Evaluation of the Performance of the Radar Integrated Nowcasting System (RaINS) During the Heavy Rainfall Episode which Caused Flooding in Penang, Malaysia on 5 November 2017, Tropical Cyclone Research and Review, Vol. 7, No. 4, 2018, pp. 217-229,
[21] D. Yang, S. Shen, L. Shao, A study on Blending Radar and Numerical Weather Prediction Model Products in Very Short-range Forecast and Nowcasting, Proceedings of SPIE, Vol. 7498, 2009,