Effect of Inclusion of a Synthetic Vortex on the Prediction of a Tropical Cyclone over the Bay of Bengal Using a Mesoscale Model

Abstract

Tropical cyclones form over the data-sparse sea regions and hence are analyzed very poorly. This results in initial errors, which may impact on the cyclone track forecast. A solution to the above is to remove the weak initial vortex and replace it with a synthetic vortex (with the correct size, intensity and location) in the initial analysis. The objective of this study is to investigate the impact of introducing a synthetic vortex (based on the NCAR-AFWA scheme) using the regional model MM5 on a tropical cyclone, which formed over the Bay of Bengal during November 2002. It is found that inclusion of the synthetic vortex has caused improvement in the simulation of wind asymmetries and warm temperature anomalies. The central minimum pressure and the maximum wind speed of the simulations with synthetic vortex are lower by 12 hPa and higher by 12 m sec –1 as compared to the simulations without the synthetic vortex. Also, this has resulted in a considerable reduction of the track prediction errors: 168 km in 06 hours, 109 km in 12 hours, 332 km in 18 hours, 601 km in 24 hours and 126 km in 30 hours of forecast. However, the impact of synthetic vortex reduces after 30 hours and the track error is higher by 80 km in 36 hours and 284 km in 42 hours of forecast.