Synoptic Drivers of Tropical Cyclone Senyar and Long-term Change in Near-Equatorial Tropical Cyclones over the Maritime Continent

Tropical Cyclone (TC) Senyar was a rare near-equatorial TC that severely impacted the western Maritime Continent (MC). It formed within the narrow Malacca Strait under weak Coriolis forcing, indicating the critical role of synoptic-scale forcing in cyclogenesis. Northeasterly cold surges accompanied its development, resembling those during Typhoon Vamei in 2001, but with a stronger easterly component that redirected moisture toward the Malacca Strait. Simultaneously, strengthened westerlies over the eastern Indian Ocean associated with a negative Indian Ocean Dipole persisted. The convergence of easterlies and westerlies around a background positive vorticity continuously intensified the initial vortex and influenced the TC propagation. Analysis of two historical climate periods reveals a significant increase in near-equatorial TCs over the MC, underscoring the growing importance of understanding TC dynamics and impacts in the region.