Baseline Climatology of Tornadoes and Waterspouts in the Philippine Archipelago

arXiv:2609.01692v2 Announce Type: new Abstract: Tornadoes are documented on every inhabited continent, yet the environmental conditions used to anticipate them were developed and validated overwhelmingly on mid-latitude records, leaving tropical regimes largely unexamined. Here, we collected 1,186 combined tornado and waterspout reports in the Philippines spanning the early 1900s to 2025 and paired each with an ERA5 proximity sounding to construct the first baseline climatology and environmental characterization of these events in the archipelago. Activity concentrates in three corridors, mostly flanked by mountain ranges, one in each major island group, and is sharply phased within a May-October window that closely tracks the annual cycle of thunderstorm frequency, peaking in August and lagging into October for waterspouts alongside the tropical cyclone season. These events cluster in the mid-to-late afternoon, consistent with daytime heating regime rather than nocturnal convection. The environments are thermodynamically permissive but kinematically shallow with Convective Available Potential Energy (CAPE) exceeds typical Great Plains values while 0-6 km bulk wind difference (BWD) stays below 10 kt, diverging the mid-latitude covariance in which instability and shear increase together. Although streamwise vorticity is modest in magnitude, nearly all discriminating variance resides in the lowest kilometer, where 68-79\% of near-surface horizontal vorticity is streamwise, reaching > 0.005 s$^{-1}$ and 96\% streamwiseness in the most organized profiles, and the hodographs retain low-level curvature. Consequently, composite indices underestimate even as tornadoes and waterspout recur. Thus, mid-latitude calibrated parameters can therefore misdiagnose tropical-maritime regimes and recalibration toward shallow-layer, orientation-aware kinematic discriminators may recover the diagnostic signal.