Projected Changes in ENSO-driven Regional Tropical Cyclone Tracks

Simulations and projections of the El Niño Southern Oscillation’s (ENSO’s) influence on TC track variability was analysed globally using Coupled Model Intercomparison project Phase 5 (CMIP5) models. The ability of these models to simulate the historical (1970–2000) ENSO–TC track relationship and inform us of the likely projected changes resulting from high carbon emissions (RCP8.5) in a climate projection (2070–2100) was determined through cluster analysis. The number of seasonal TC occurrences during traditional ENSO events (“El Niño” and “La Niña”) in each cluster were used to determine whether each cluster was “El Niño dominant”, “La Niña dominant” or “neither”. Only seven out of a combined total of 28 clusters across all basins were found to disagree in terms of “ENSO dominance” between the observed records and historical model simulations. This suggests that models can simulate the ENSO and TC track relationship reasonably well. Under sustained high carbon emissions, La Niña TCs were projected to become dominant over El Niño TCs in the central South Indian Ocean (~ 60–100°E), the southern Bay of Bengal and over straight-moving TCs in the South China Sea. El Niño TCs were projected to increase and become dominant over La Niña TCs in a larger area of the western South Pacific (~ 160°E–165°W) and central North Pacific (~ 160°E–145°W) Oceans. Projections of track directions and lifetimes, while less robust, indicated that El Niño TCs would track westward more often in the Coral Sea (150–165°E), while El Niño TCs that took an eastward track here would have longer lifetimes (~ 3 days).