Tropical cyclones (TCs), also referred to as hurricanes or typhoons, are amongst the deadliest and costliest natural hazards, affecting people, economies, and the environment in coastal areas around the globe when they make landfall. TCs are projected to become more intense in a warming climate, enhancing the risks associated with their wind speeds, precipitation and storm surges. It is therefore crucial to minimize future loss of life and by performing accurate TC risk assessments for coastal areas. Calculating TC risk at a global scale, however, has proven to be difficult, given the limited temporal and spatial information on landfalling TCs around much of the global coastline, and how this is going to change under climate change.

To overcome these limitations, we developed a novel approach to calculate TC risk under present and future climate conditions using the newly developed Synthetic Tropical cyclOne geneRation Model (STORM). STORM is a fully statistical model that can take any input dataset and statistically resamples this to an equivalent of 10,000 years of TC activity under the same climate condition. The resulting STORM dataset contains of enough TC activity in any coastal region of interest to adequately calculate TC probabilities and risk from. In this presentation, we discuss the STORM model and present applications of the STORM synthetic datasets to a variety of TC-risk related questions.

We will then zoom in on one of such applications, in which calculate future changes in storm surge probabilities along the Vietnamese coastline. Viet Nam is a rapidly developing country and, with 70% of its population living in coastal areas, it is highly exposed to flooding from coastal, fluvial and surface runoff sources. Densely populated communities in low-lying regions of the Red and Mekong delta are especially vulnerable to flooding. We force a hydrodynamic model with the new synthetic STORM database representing 10,000 years of past/present and future tropical cyclone activity, to investigate climate change impacts on extreme sea levels forced by storm surges (± tides). We show that, as stronger tropical cyclones likely pass through this region and become more numerous over the next 30 years, both the spatial extent and severity of storm surge hazard increases. While extreme storm surge events thus become a more frequent occurrence generally, larger storm surges around Vietnam and China coastlines are projected to be a particular future hazard. This would acutely impact the future populations of low-lying zones such as the Red and Mekong River deltas. Sections of Cambodian and Thai coastline are also projected to face previously unseen storm surge hazards.