Localized Tornado Outbreak at the Upstream of a Tropical Easterly Wave in Camarines Norte, Philippines (13 September 2025)

Abstract

(Abridge) On 13 September 2025 around 22 UTC, a localized tornado outbreak affected eastern Philippines, causing significant damage in Camarines Norte. The event developed within an atypical easterly severe weather regime characterized by warm, moist southeasterly flow and strong low-level wind shear associated with an easterly wave trough. A vorticity convergence zone along the inverted trough enhanced low-level rotation, while highly curved streamwise hodographs indicated a favorable environment for supercells and tornadogenesis. At least five vortices were identified, including three tornadic supercells. The Magang tornado was rated IF2.5 (EF3-equivalent) with $\sim$2 km damage path, while the Cahabaan and Napilihan tornadoes were rated IF1 (EF1-equivalent), with Cahabaan producing $\sim$3 km damage path. The remaining vortices were rated IF0 (EF0-equivalent). These tornadoes occurred simultaneously, indicating multiple discrete supercells within the same mesoscale environment and possible inflow-outflow interactions. Dual-polarization radar observations revealed Z$_\text{DR}$ and K$_\text{DP}$ columns, a debris signature in the Magang tornado, and a bounded weak echo region (BWER) in the Cahabaan supercell. This study documents the first known tornado outbreak and simultaneous tornadic supercells in the Philippines within an easterly severe weather regime.