Investigating the Influence of Anthropogenic Forcing and Natural Variability on the 2014 Hawaiian Hurricane Season Bulletin of the American Meteorological Society

Three hurricanes approached the Hawai-ian Islands during the 2014 hurricane season (Fig. 23.1a), which is the third largest number since 1949 (black bars in Fig. 23.1b). Previous studies suggest that the frequency of tropical cyclones (TCs) around Hawaii will increase under global warming (Li et al. 2010; Murakami et al. 2013). The projected increase is primarily associated with a northwestward shifting of TC tracks in the open ocean southeast of the islands, where climate models robustly predict greater warm-ing than the other open oceans. Natural variability, such as that associated with the El Niño–Southern Oscillation (ENSO), also has a significant inf luence on TC activity near Hawaii (Chu and Wang 1997; Jin et al. 2014). In fact, moderate El Niño conditions were observed during the 2014 hurricane season that might have been favorable for TC activity near Hawaii. In this study, we use a suite of climate experiments to explore whether the unusually large number of Hawaiian TCs in 2014 was made more likely by an-thropogenic forcing or natural variability. Grant no. NA14OAR4830101