A Case Study of the Tornadic Supercell in the Province of Pampanga, Philippines (27 May 2024)

This study provides an integrated damage assessment, visual evaluation, environmental context, and remote sensing analysis of the tornado event that struck the suburb of Candating in Arayat, Pampanga on 27 May 2024. Satellite imagery and ground-level damage photographs reveal a $\sim$2 km path, with damage reaching EF2 intensity at one point along the track, based on the Enhanced Fujita (EF) scale. Videos of the tornado and its parent storm reveal a well-defined wall cloud and low-level mesocyclone. Subsequent radar analysis supports these and other features of a tornadic supercell. Synoptic-scale ascent in the mid- and upper-troposphere was subtle, influenced by the approach of Tropical Cyclone Ewiniar. However, a modest meridional flow aloft provided sufficient deep-layer shear to support supercell development. The southwest monsoon acted as a low-level jet, promoting warm, moist advection into western Luzon. The supercell developed around midday and was characterized by large-undiluted instability, attributed to steep low-level lapse rates. Although low-level shear and the associated near-surface horizontal vorticity were weak, the latter is highly streamwise, allowing for efficient ingestion, tilting, and stretching into vertical vorticity, which aided in tornadogenesis. Both satellite and radar data suggest that storm interactions, such as a nudging mechanism and terrain effects from nearby Mt. Arayat may have contributed to the initiation and intensification of the supercell through lee-side convergence and vorticity enhancement. The complex tropical environment of the Candating, Arayat tornado exhibits several similarities to well-documented tornadic events in North America. These findings highlight the need for further research into the atmospheric conditions conducive to tornadic activity in the Philippines.

💡 Research Summary

This paper presents a comprehensive case study of the tornado that struck the suburb of Candating in Arayat, Pampanga Province, Philippines, on 27 May 2024. The authors combine ground‑based damage surveys, eyewitness photographs and videos, satellite imagery, radar observations, and reanalysis data to document the event’s characteristics and to diagnose the atmospheric environment that produced a tornadic supercell in a tropical setting.

The damage assessment shows a roughly 2 km long damage path with a peak intensity of EF2 (wind speeds 111–154 km h⁻¹) at one location. High‑resolution ground photographs reveal extensive structural failure consistent with strong rotation and updraft. Satellite data (GOES‑16) captured a well‑defined wall cloud and a low‑level mesocyclone preceding the tornado, while WSR‑88D radar displayed classic tornadic signatures: a hook echo, bounded weak echo region, and strong dual‑polarization velocity couplets.

Environmental analysis relies on ERA5 reanalysis at 0.25° × 0.25° resolution with hourly output for 04, 05, and 06 UTC. The synoptic picture was dominated by the southwest monsoon, which produced a low‑level jet of ~20 m s⁻¹ at 850 hPa, transporting warm, moist air into western Luzon. The approaching tropical cyclone Ewiniar contributed only weak mid‑ and upper‑level ascent, but the monsoonal flow supplied sufficient deep‑layer shear (meridional flow aloft) to support supercell development. Thermodynamic profiling shows extremely high instability: CAPE values exceed 2500 J kg⁻¹, ECAPE around 1800 J kg⁻¹, LFC below 800 m, and LCL near 600 m, indicating that buoyant parcels could rise from the surface with minimal inhibition.

Shear metrics differ from classic Great Plains supercells. Bulk wind differences (BWD) are modest (0–1 km BWD ≈ 12 m s⁻¹, 0–3 km BWD ≈ 20 m s⁻¹), yet storm‑relative helicity (SRH) is substantial: SRH₀₋₁km ≈ 150 m² s⁻² and SRH₀₋₃km ≈ 250 m² s⁻². Crucially, the low‑level (0–500 m) streamwise vorticity is strong (≈ 0.03 s⁻¹), providing an efficient “in‑and‑up” pathway whereby horizontal vorticity is ingested, tilted, and stretched by the updraft. This streamwise alignment compensates for the relatively weak shear and is identified as a key driver of tornadogenesis in this case.

Topographic influences are also highlighted. Mt. Arayat, situated just east of the tornado track, likely induced lee‑side convergence that locally enhanced upward motion, aiding the initiation of the supercell. Additionally, interactions with neighboring convective systems (a nudging mechanism) appear to have reinforced the mesocyclone, further promoting tornadic development.

The authors argue that tropical environments can produce tornadic supercells even when classic deep‑layer shear is modest, provided that (1) low‑level moisture and instability are extreme, (2) streamwise vorticity is strong and aligned with the storm inflow, and (3) terrain‑induced convergence or mesoscale forcing is present. This expands the conventional tornado‑formation paradigm, which has been largely based on mid‑latitude cases, and underscores the need for region‑specific forecasting tools.

The study also notes the scarcity of systematic tornado documentation in the Philippines. Project SWAP (Severe Weather Archive of the Philippines) played a pivotal role in gathering and verifying the observational dataset, illustrating the value of coordinated citizen‑science networks. The authors recommend expanding such platforms, integrating high‑resolution numerical modeling, and deploying dedicated observational assets (e.g., mobile radars, drones) to improve understanding and warning capabilities for tropical tornadoes.

In summary, the Candating tornado provides a rare, data‑rich example of a tornadic supercell in the Philippines, demonstrating that strong low‑level streamwise vorticity, intense instability, and terrain‑related forcing can combine to produce EF2‑scale tornadoes in a tropical monsoon environment. The findings have important implications for severe‑weather research, operational forecasting, and disaster risk reduction in the Philippines and other tropical regions.