The Ninth International Workshop on Tropical Cyclones (IWTC-9) took place in Hawaii, USA in December 2018. This review paper was presented at the Workshop under the Tropical Cyclone Track topic. The forecasting of tropical cyclone (TC) track has seen significant improvements in recent decades both by numerical weather prediction models and by regional warning centres who issue forecasts having made use of these models and other forecasting techniques. Heming and Goerss (2010) gave an overview of forecasting techniques and models available for TC forecasting, including evidence of the improvement in performance over the years. However, the models and techniques used for TC forecasting have continued to develop in the last decade. This presentation gives an updated overview of many of the numerical weather prediction models and other techniques used for TC track prediction. It includes recent performance statistics both by the models and the regional warning centres.

This contribution summarizes key research advances on tropical cyclone (TC) intensity change from 2014-2018 from the Ninth International Workshop on Tropical Cyclones (IWTC-9). Research advances on intensity change have occurred on many fronts, including improved understanding of the role of vertical wind shear (VWS) and its impact on convection, surface fluxes, ocean eddies, dry/dusty air intrusions, eyewall replacement cycles (ERCs), spiral rainband dynamics, eyewall instability and inner-core mixing, and the mechanisms by which TCs intensify. This summary highlights a number of these important advances. Additionally, some new and emerging topics on TC intensity change have recently been elucidated: the important role of vortex structure on the subsequent intensification rate, the maximum potential intensification rate (MPIR), and the role of upper level outflow on TC intensity change.

This review summarizes experiences at operational centers to forecast tropical cyclone (TC) intensity change as presented to the International Workshop on Tropical Cyclones (IWTC-9) in Hawaii in 2018. Some operational forecast centers have been able to leverage advances in intensity guidance to increase forecast skill, albeit incrementally, while others have struggled to make any significant improvements. Rapid intensity changes continue to present major challenges to operational centers and individual difficult cases illustrate the forecasting challenges. It is noteworthy that the realization of a recommendation from IWTC-8 in 2014, to adapt guidance initially developed for the North Atlantic and North-East Pacific to other basins, has led to improved forecast skill of some agencies. Recent worldwide difficult cases are presented so that the research community can further investigate, potentially leading to improved intensity forecasts when similar cases are observed in the future.  

Since the Eighth International Workshop on Tropical Cyclones (IWTC-8), held in December 2014, progress has been made in our understanding of the relationship between tropical cyclone (TC) characteristics, climate and climate change. New analysis of observations has revealed trends in the latitude of maximum TC intensity and in TC translation speed. Climate models are demonstrating an increasing ability to simulate the observed TC climatology and its regional variations. The limited representation of air-sea interaction processes in most climate simulations of TCs remains an issue. Consensus projections of future TC behavior continue to indicate decreases in TC numbers, increases in their maximum intensities and increases in TC-related rainfall. Future sea level rise will exacerbate the impact of storm surge on coastal regions, assuming all other factors equal. Studies have also begun to estimate the effect on TCs of the climate change that has occurred to date. Recommendations are made regarding future research directions.