Prediction And Predictability Of Landfalling Typhoon Vicente(2012) Through EnKF Data Assimilation Of Doppler Observations

The current study explores the use of an ensemble Kalman filter (EnKF) based on the Weather Research and Forecast (WRF) model to continuously assimilate the high resolution Doppler radar data in order to examine the evolution and three-dimensional (3-D) structure as well as the predictability and dynamics of Typhoon Vicente (2012). This is an intense Western Pacific tropical cyclone that made landfall around2000UTC23July2012near the Pearl River Delta region of Guangdong Province, China with a peak10-m wind speed around40m s-1along with considerable inland flooding. With vortex and dynamics dependent background error covariance estimated by the short-term ensemble forecasts, it was found that the WRF-EnKF could efficiently assimilate the high temporal and spatial resolution3-D radar radial velocity to improve the depiction of the typhoon inner-core structure of Vicente which further improved the forecasts of the track and intensity along with the associated heavy precipitation. The WRF-EnKF analyses and forecasts along with the ensembles initialized from the EnKF perturbations at different time were further used to explore the dynamics and predictability of Vicente with respect to the number of volumes of radar observations being assimilated, different lead times before and during the landfall. The ensemble forecasts and sensitivity analyses were further used to explore the leading dynamics that controlled the prediction and predictability of track, intensity and rainfall during and after its landfall.The purpose of this study is to explore for the first time the use of EnKF to directly assimilate China Doppler radar radial velocity observations near the peak intensity period for convection-permitting analysis and prediction of Typhoon Vicente (2012) during and after its landfall in South China. Results of this work clearly demonstrated the significance and potential of assimilating land-based Doppler radar observations with an EnKF in the initialization and prediction for intense coastal storms such as Vicente. It provided a good example for the potential benefits of assimilating coastal radar data using ensemble based data assimilation technique, thus could be greatly helpful for operational typhoon forecast. Besides, this work also demonstrated the capability of the EnKF in effectively ingesting the radar data even near the peak stages of a tropical cyclone, which complements previous works on assimilating radar data when the TC is not very strong.