Prediction of Rapid Intensification, Eyewall Replacement Cycle, and Inner-Core Structure of ESCS Phailin

Abstract The present study evaluated the model forecasted intensity, rapid intensification (RI), secondary eyewall formation (SEF), eyewall replacement cycle (ERC), and associated structural features of an extremely severe tropical cyclone that made landfall along the east coast of India. The study utilized the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) Model to forecast an extremely severe tropical cyclone Phailin that made landfall on the Odisha coast of eastern India on 12 October 2013, using three different model resolutions (5, 3, and 1.667 km) and forced with different initial conditions. Model-simulated results were compared with available observations obtained from the Joint Typhoon Warning Center (JTWC) best-fit track, Indian Monsoon Data Assimilation and Analysis (IMDAA), Doppler weather radar (DWR), and satellite-based datasets. Key findings from this study reveal that the cyclone intensity, in terms of maximum surface wind and minimum sea level pressure, rapid intensification, secondary eyewall formation, eyewall replacement cycle, and associated structural features are well simulated by the model with 1.667-km horizontal resolution. Results indicate that simulated tropical cyclone intensity and structure were poorly forecasted by the 5-km grid but were better simulated by the 1.667-km grid. Furthermore, the simulated cyclone structure, in terms of relative humidity, microphysics latent heating, latent heat flux, and reflectivity, was much better forecasted using the 1.667-km grid. Findings from the study also indicate that the model should essentially be initialized at least 76 h before landfall for improved prediction of ERC, and a model resolution of less than 2 km could essentially resolve the SEF and ERC for intense cyclonic systems in the north Indian Ocean.