Performance of WRF-ARW winds on computed storm surge using hydodynamic model for Phailin and Hudhud cyclones

Extreme weather events such as tropical cyclones can lead to storm surge during the time of landfall inundating low lying coastal areas. Storm surge computations are sensitive to input wind forcing and local bathymetric gradients especially during the landfall time of cyclones. Therefore, it is an essential pre-requisite to specify accurate wind field and mean sea level pressure as a primary input to hydrodynamic models in order to compute precisely the peak storm surge and its envelope including the extent of coastal flooding. The present study performs a comprehensive analysis on storm surge computation utilizing WRF-ARW (version 3.7.1) winds run with three different grid resolutions for the recent very severe cyclonic storms Phailin and Hudhud that had landfall along the east coast of India. The study considers two different sets of WRF-ARW winds constructed using GFS and FNL initial conditions under three varied horizontal grid resolutions. In addition the study explores the efficacy of the best possible Combination considering the initial conditions together with different grid resolutions for Phailin and Hudhud cyclones. Further, numerical experiments conducted with these different wind combinations provided an opportunity to ascertain the characteristics of storm surge development and its spatial variability along the coast. The study highlights that the 3 km grid resolution performed the best during both these cyclonic events having implications on storm surge prediction.