Evaluation of the Hurricane Weather Research and Forecasting (HWRF) model for tropical cyclone forecasts over the North Indian Ocean (NIO)

The Hurricane Weather Research and Forecast (HWRF) model, which was operational at the US National Centers for Environmental Prediction, was ported in India Meteorological Department (IMD) for its operational tropical cyclone (TC) track and intensity forecast at Regional Specialised Meteorological Center, New Delhi. As part of the validation of the model, case studies of nine major TCs formed during the 2010-2013 seasons over the Bay of Bengal and the Arabian Sea of the North Indian Ocean were examined to test the ability of the model for Indian Seas. The model was integrated for 5-day forecasts with basic input from the IMD Global Forecast System spectral fields. The model's basic fields as well as track and intensity errors are evaluated. The average track errors for these nine cases were found to be 83 km at 12 h, 135 km at 24 h, 176 km at 36 h, 186 km at 48 h, 233 at 60 h, and 319 km at 72 h. The HWRF track forecast errors displayed an improvement of 7, 27, 25 and 15 % over the IMD operational forecasts at 36, 48, 60, and 72 h, respectively. The model with high-resolution 3 km nest displayed a significant improvement in track forecasts with 12-46 % over the model with 9-km resolution nest. However, the HWRF model intensity forecasts displayed only marginal improvement of 5-8 % over the IMD operational forecasts.