Estimation of tropical cyclone intensity and location over the north Indian Ocean – a challenge

Abstract

Maximum wind speeds associated with tropical cyclones are estimated operationally by a very widely used tool, the satellite‐based Dvorak technique (SDT) of cloud pattern matching and infrared cloud‐top temperature analyses, but it still has its own limitations. To make a good forecast and its proper verification it is essential to estimate the location and current intensity of a cyclone accurately. This study compares intensity estimates of tropical cyclones over the north Indian Ocean by the Joint Typhoon Warning Center (JTWC) and the Regional Specialized Meteorological Centre, New Delhi (RSMCND). The results show that, except for super cyclones, the differences in intensity estimates are a function of intensity, the 12 hr intensity trend and the translation speed. The intensity estimates by the JTWC are often higher than RSMCND estimates. The mean absolute difference (MAD) and the root mean square difference (RMSD) are 9.7 kt and 13.3 kt respectively. The MAD ranges from 5.9 kt to 15.6 kt and the RMSD ranges from 7.6 kt to 19.0 kt. The average difference in location estimation and the corresponding standard deviation are found to be 67 km and 54 km respectively. In view of the subjectivity in SDT‐based intensity estimation which largely depends on the skill of the individual analyst, a robust objective method should be adopted to achieve uniformity in intensity estimates across agencies. The results of this study and the factors affecting intensity estimates quantified in the study will help operational forecasters for better monitoring of tropical cyclones and better post storm best‐track data analysis.