Sea surface temperature-forced and atmospheric internal variability of tropical cyclone genesis latitude in the northwest Pacific

Abstract

Tropical cyclone (TC) genesis latitude in the northwest Pacific (NWP) exhibits strong year-to-year variations. Combining observations with a 100-member ensemble of TC-permitting atmospheric model simulations, we examine the oceanic forcing and atmospheric internal variability in these variations. Results show that sea surface temperature (SST)-forced variability, largely modulated by the tripolar pattern of Pacific SST variability, explains 53.3% of the total variance in the NWP TC genesis latitude. Atmospheric internal variability, indicated by the fluctuations in the subtropical precipitation over the NWP, contributes an additional portion to the year-to-year variations. Leveraging the identified indicators for the SST-forced and atmospheric internal variability, an empirical reconstruction model is developed, which skillfully reproduces the TC genesis latitude in the NWP, as demonstrated by the statistically significant correlations in both cross-validated reforecast for 1981–2010 and independent forecast for 2011–2024. Further decomposition of seasonal-mean TC genesis latitude reveals that while changes in monthly-mean genesis latitude dominate the total variations, shifts in TC seasonality play a crucial role during years with extreme northward/southward displacements. These findings highlight the synergetic influence of oceanic forcing and atmospheric internal variability on TC genesis latitude and provide a foundation for improving seasonal TC activity predictions.