Development of India Meteorological Department: High Resolution Rapid Refresh (IMD-HRRR) Modeling System for Very Short Range Weather Forecasting

The aim of this study is the operational dynamical nowcasting application over different parts of India from Indian Meteorological Department (IMD) using Doppler Weather Radar (DWR) network of multiple radars and numerical weather prediction (NWP) model. The High Resolution Rapid Refresh (HRRR) approach has been adopted to achieve this objective in which the DWR data are hourly assimilated at convective-scale in the Weather Research and Forecasting (WRF) model. The designated NWP setup implemented for very short-range to nowcasting of weather is defined as the IMD-HRRR modelling system. Various quality controls are employed before assimilating DWR data in the IMD-HRRR system. Three different domains are specified over India that cover the entire Indian landmass, and next 12-h predictions are provided from hourly cyclic assimilation experiments. The results of all domains suggested that the IMD-HRRR predictions are not degraded with forecast lengths (up to 12 h) when compared against observations e.g. Synop, Metar, Buoy, total precipitable water (TPW) from GPS stations. Minimum errors are achieved when model predictions are compared against Buoy and TPW observations. The correlation values are higher than 0.9 for all domains. Furthermore, the IMD-HRRR model forecasts are also compared with observed DWR radial winds to demonstrate auxiliary applications of the DWR data for model verifications at high spatio-temporal resolution.