Advances and trends in tropical cyclone research and forecasting：An overview of the ninth World Meteorological Organization International Workshop on Tropical Cyclones （IWTC-9）

The ninth World Meteorological Organization International Workshop on Tropical Cyclones (IWTC-9) was held in Hawaii, the U. S., in December 2018. Recent global advances in tropical cyclone research and forecasting and warning operations were thoroughly reviewed, and a corresponding outlook was illustrated in this workshop. In the past four years (2015—2018), significant progress has been made in research on the effects of tropical waves and convection on tropical cyclogenesis, complex environments influencing tropical cyclone recurvature, the mechanisms of convection and vertical wind shear for tropical cyclone intensity changes, the mechanisms of concentric eyewall formation and replacement, the response of extratropical transition to environmental conditions, the characteristics of tropical cyclone climate change, and multi-platform observation techniques for tropical cyclones. In addition, there have been promising developments in the probabilistic forecasting of tropical cyclone formation, the improvement of tropical cyclone intensity forecasting in global models, operational forecasting techniques for sub-seasonal tropical cyclone activity and the theory of tropical cyclone forecasting uncertainty. The outcomes of IWTC-9 will be reviewed here, and the direction of tropical cyclone research and operational development in China will be discussed as well.