Improvement of wind field forecasts for tropical cyclones over the North Indian Ocean

Abstract

This paper demonstrates a modification method for real-time improvement of wind field forecasts for a typical cyclone VARDAH, which formed over the Bay of Bengal (BoB) in 2016. The proposed method to improve the wind field forecasts associated with tropical cyclone consists of two components. The first one is the relocation method, which relocates the wind field forecasts obtained from the Global Forecast System(GFS) data of National Centres for Environmental Prediction(NCEP). The relocation of the model forecasts wind field is made on forecast locations generated by Multi Model Ensemble (MME) track forecast of India Meteorological Department(IMD). The second one is the modification of wind speed, which directly modifies the NCEP GFS wind speed forecasts based on intensity forecasts by Statistical Cyclone Intensity Prediction(SCIP) model of IMD. Applying these two methods, the displacement of wind field and underestimation/overestimation of wind speed in the model forecast field can be improved. Both modification methods show considerable improvements in the displacement and speed of wind field forecasts. The displacement error of wind field is found to have improved by about 51% at 48 h and about 80% at 72 h forecast. Overestimation of maximum wind speed in the forecast field is found to be improved by about 88% at 48 h and about 38% at 72 h forecast. The spatial distributions of corrected wind speed forecasts are also found to be more analogous than direct model forecasts with the corresponding analysis wind at all forecast hours. Two proposed modification methods could provide improved wind field forecast associated with tropical cyclones in real-time.