Baseline Climatology of Tornadoes and Waterspouts in the Philippine Archipelago

Abstract

Tornadoes are documented on every inhabited continent, yet the environmental condition used to anticipate them was developed and validated overwhelmingly on mid-latitude records, leaving tropical regimes largely unexamined. Here, we collected 1,186 tornado and waterspout reports combined 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 severe weather 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. The environments are thermodynamically permissive but kinematically shallow as mean convective available potential energy exceeds typical Great Plains values, while bulk wind difference between the 0-6 km layer stays below 10 kt, diverging from the mid-latitude covariance in which instability and wind shear increase together. Nearly all of the discriminating variance instead resides in the lowest kilometer, where 68-79% of the near-surface horizontal vorticity is streamwise, reaching 96% in the most organized profiles, and the hodographs retain low-level curvature. Consequently, composite indices underestimate even as tornadoes recur, and locally rescaled thresholds are required. Therefore, mid-latitude calibrated convective parameters can misdiagnose tropical-maritime regimes.