Study on the Formation and Evolution of Tropical Cyclone Over Bay of Bengal Using Weather Research & Forecasting (WRF) Model

Abstract

In the tropics the tropical cyclone is one of the most disastrous atmospheric phenomena of the tropics, which forms over the warm oceans and ravage life and property especially over the coastal belt due to extremely strong winds and associated storm surges at the time of landfall. The Bay of Bengal is highly vulnerable to tropical cyclogenesis. To save the life and minimize the damages it is necessary to make advance warning and prediction of tropical cyclone quite ahead of time. Therefore a study has been conducted to investigate the formation, evolution, structure, track and landfall of tropical cyclones using Advanced Research WRF (ARW) model. The study has been performed for three land falling tropical cyclones of different intensities formed in the Bay of Bengal and had their landfall to the coast of Bangladesh, Myan mar and east coast of India. These are very severy cyclonic storm Nargis (2008), very severy cyclonic storm Thane (2011) and cyclonic storm Mahasen (2013). The model has been set for the Bay of Bengal basin at 9 km horizontal resolution with Kain-Fritch (KF) cumulus parameterization, WRF-single moment (WSM) 3-class microphysics and Yonsei University PBL schemes. The GFS resolution has been used as initial field and lateral boundary conditions. The present study shows that the ARW model is capable of forecasting the formation of the first low pressure system 24 hrs ahead from its actual genesis without incorporation of any artificial vortex and is capable to forecast the formation of the first depression. The model successfully simulates the realistic evolution process and more or less realistic intensification of tropical cyclones. For some cases the model under estimated the intensity of the cyclonic system. The model results indicate that the longer range prediction provides better intensity forecast. The model generates a realistic structure of the tropical cyclones with high spatial details. This has been possible due to the higher spatial resolution of the regional model. One of the outstanding findings of the study is that the model has successfully predicted the tracks, recurvature and time of landfall of the selected tropical cyclones with high accuracy even in the 96 hrs prediction. Therefore the model has high potential to predict the formation, evolution, intensity, track and landfall of the tropical cyclones of the Bay of Bengal.