Recent progress in research and forecasting of tropical cyclone outer size

This review article summarizes the current understanding and recent updates to tropical cyclone outer size and structure forecasting and research primarily since 2018 as part of the World Meteorological Organization's 10th International Workshop on Tropical Cyclones. A more complete understanding of tropical cyclone outer wind and precipitation is key to anticipating storm intensification and the scale and magnitude of landfalling hazards. We first discuss the relevance of tropical cyclone outer size and structure, improvements in our understanding of its life cycle and inter-basin variability, and the processes that impact outer size changes. We next focus on current forecasting practices and differences among warning centers, recent advances in operational forecasting, and new observations of the storm outer wind field. We also summarize recent research on projected tropical cyclone outer size and structure changes by the late 21st century. Finally, we discuss recommendations for the future of tropical cyclone outer size forecasting and research.