Meridional Migration of Eastern North Pacific Tropical Cyclogenesis: Joint Contribution of Interhemispheric Temperature Differential and ENSO

Abstract

AbstractThis study finds that the meridional migration of tropical cyclogenesis (TCG) between June and November over the eastern North Pacific is mainly due to changes in the Hadley circulation and associated changes in the location of the intertropical convergence zone as modulated by ENSO and the interhemispheric temperature differential (ITD). These two factors are largely independent of each other and play significant and nearly equivalent roles in the meridional migration of TCG over the ENP from 1979 to 2018. Through the use of regression models, we find that the combination of these two factors has significant skill in capturing annual TCG meridional distribution over the ENP basin. June–October ENSO, as defined by Niño‐3.4, can be skillfully predicted with ∼1 season lead time, while ITD can be skillfully predicted ∼3 seasons in advance. This predictability allows for the potential for seasonal outlooks of TCG meridional movement over the ENP. The influence of ITD on TCG meridional migration over the ENP has repercussions on climate change timescales as well, due to the potential TCG meridional migration over the ENP in response to global warming. Under the Shared Socioeconomic Pathways 2–4.5 scenario, the ITD shows a robust increase among the 23 models of version 6 of the Coupled Model Intercomparison Project. However, the considerable uncertainty in the model response of ENSO to global warming reduces confidence in projections of TCG meridional migration over the ENP.