Future Changes in Historically-Impactful Tropical Cyclone Events Using Convection-Permitting “Storyline” Simulations
Tropical cyclone (TC) risk depends on multiple factors, including the severity of TC hazards and the probability of TC occurrence. Although future changes in TC occurrence remain uncertain, substantial advances have been made in projecting future changes in the severity of TC hazards, including associated wind, precipitation, storm surge, and tornadoes. These advances have been enabled in part by considering how historically-impactful TC events could change if similar events were to happen in a future warmer climate. Here, we applied this “storyline” approach using high-resolution regional model simulations, in which historically-impactful TC events were first hindcasted under the actual synoptic conditions and climate state in which they occurred. After verifying that the hindcast quality is reasonable, we then performed experiments representing the TC events if they were to occur in the future, by retaining the original synoptic conditions but perturbing the climate state to represent a future warmer climate. We investigated how several TCs that produced the greatest TC-tornado outbreaks on recent record in the U.S., including Hurricanes Ivan (2004), Frances (2004), Rita (2005), Katrina (2005), and Harvey (2017), could change in the future. Convection-permitting simulations revealed a robust future increase in the occurrence of TC-tornado surrogates. In addition, we investigated how future projections of TC characteristics could be sensitive to the treatment of the ocean (i.e., using prescribed sea-surface temperatures compared to atmosphere-ocean coupling). We found that although the sign of future wind and precipitation changes is insensitive to the treatment of the ocean, the magnitude of future TC precipitation changes can vary substantially depending on the treatment of the ocean. In addition, the simulations project robust future increases in TC precipitation and size. This research aims to provide the best possible information on how several important aspects of TC risk could impact coastal and island communities in the future, by focusing on events for which there is a historical context.