Observed Interseasonal Variability of Tropical Cyclone Rapid Intensification

Tropical cyclones present a major threat to the livelihood, infrastructure, and economy of coastal and adjacent inland communities. Major (Category 3+) tropical cyclones present the most acute risk, given these storms cause the majority of tropical cyclone-related damage. While forecasts of tropical cyclone tracks have improved over recent decades, forecasts of tropical cyclone intensity have remained challenging. One reason for this challenge is the tendency for major tropical cyclones to rapidly intensify (>=30 kt intensification in <=24 h). It is well known that the majority of major tropical cyclones undergo rapid intensification, but predicting the timing and magnitude of rapid intensification has remained challenging.

While many studies have focused on the prediction of rapid intensification for individual tropical cyclones, this study focuses on interseasonal drivers of rapid intensification. In this study, we examine how rapid intensification is modulated by various climate modes with a focus on ENSO. We find that rapidly-intensifying storms occur more frequently in the North Atlantic during La Niña, while rapidly-intensifying storms occur more frequently in the eastern North Pacific, western North Pacific and South Pacific during El Niño. In addition to basinwide changes of frequency, we also observe considerable shifts of rapid intensification location based on ENSO phase. For example, western North Pacific tropical cyclones are more likely to undergo rapid intensification in the eastern part of the basin in El Niño relative to La Niña. Because of the considerable uncertainty of the future state of ENSO, there is also considerable uncertainty as to how rapidly-intensifying tropical cyclones will change in the future.