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REVIEW 2 major objections 3 minor

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

T0 review · 2 major / 3 minor · reviewed 2026-05-09 · grok-4.3

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Pith's one-line read A tropical easterly wave produced the first documented tornado outbreak in the Philippines with multiple simultaneous supercells.

desk verdict Solid observational case study of a Philippine tornado outbreak in an easterly wave, but the 'first known' claim needs a documented literature and records search to hold. read the letter →

arxiv 2604.20222 v4 pith:42SNIFSI submitted 2026-04-22 physics.ao-ph

Generich H. Capuli This is my paper · ORCID
classification physics.ao-ph
keywords tornadooutbreakeasterlywavePhilippinessupercelldual-polarizationradartropicalmeteorologytornadogenesisvorticityconvergence
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper documents a localized tornado outbreak on 13 September 2025 in Camarines Norte that formed inside an easterly wave trough. At least five vortices appeared, three of them tornadic supercells, with one reaching IF2.5 intensity and paths extending several kilometers. Radar data showed classic supercell markers including ZDR and KDP columns, a debris ball, and a bounded weak echo region, all occurring under southeasterly flow with strong low-level shear. A reader would care because the event demonstrates that environments previously considered atypical for tornadoes can still generate discrete supercells and significant damage in the tropics.

What carries the argument

The inverted trough's vorticity convergence zone acting together with streamwise-curved hodographs that organized discrete supercells and enabled tornadogenesis within the same mesoscale easterly environment.

What would settle it

A documented prior tornado outbreak in the Philippines linked to an easterly wave or a detailed reanalysis showing that the observed radar features were produced by non-supercell processes instead.

Watch

Extended reading notes

Core claim

On 13 September 2025 around 22 UTC, an easterly wave trough created a vorticity convergence zone and highly curved hodographs that supported at least three simultaneous tornadic supercells in the Philippines; dual-polarization radar confirmed the Magang supercell as IF2.5 with a debris signature, while the Cahabaan supercell exhibited a BWER and the Napilihan tornado produced a 3 km damage path.

Load-bearing premise

Radar signatures such as ZDR and KDP columns, debris signatures, and BWER together with damage surveys unambiguously identify multiple discrete tornadic supercells and that no comparable events have occurred before.

Editorial extensions

If this is right

  • Tornadoes can form simultaneously in a single easterly wave environment with inflow-outflow interactions between neighboring supercells.
  • Dual-polarization radar remains effective for identifying tornadic supercells even when the parent regime is southeasterly rather than westerly.
  • Damage surveys in the Philippines can reliably assign IF-scale ratings up to at least IF2.5 when clear paths are available.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Similar undetected outbreaks may exist in other tropical regions where radar coverage is sparse and easterly waves are common.
  • Operational forecasting in Southeast Asia could benefit from adding easterly wave diagnostics to severe-weather guidance.
  • This case supplies a concrete example for testing whether tropical climate shifts alter the frequency of low-level shear environments capable of supercell formation.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

2 major / 3 minor

Summary. The manuscript is an observational case study documenting a localized tornado outbreak on 13 September 2025 in Camarines Norte, Philippines, occurring upstream of a tropical easterly wave. It identifies at least five vortices (three rated as tornadic supercells) using dual-polarization radar signatures including ZDR/KDP columns, a debris signature, and a BWER, combined with post-event damage surveys that assign IF ratings from IF0 to IF2.5 (EF-equivalent). The environment is characterized by warm moist southeasterly flow, low-level shear, and a vorticity convergence zone along an inverted trough. The paper asserts this as the first known tornado outbreak and instance of simultaneous tornadic supercells in the Philippines within an easterly severe weather regime.

Significance. If the tornado classifications and environmental attribution hold, the work would add a rare, well-observed example of supercell tornadoes in a tropical easterly-wave setting, a regime not commonly associated with such activity in the Philippines. The dual-polarization radar features and quantified damage paths (e.g., ~2 km for the IF2.5 Magang tornado) provide concrete, falsifiable observational evidence that could inform regional severe-weather climatology and forecasting. The simultaneous occurrence of multiple discrete supercells is a noteworthy aspect of the mesoscale environment description.

major comments (2)
  1. [Abstract] Abstract: The headline claim that the event constitutes 'the first known tornado outbreak and simultaneous tornadic supercells in the Philippines within an easterly severe weather regime' is load-bearing for the paper's novelty but is not accompanied by any description of a systematic search of PAGASA archives, international severe-weather databases, or regional literature to establish the absence of prior comparable events.
  2. [Radar and damage analysis sections] Radar and damage analysis sections: The classification of three discrete tornadic supercells rests on radar signatures (ZDR/KDP columns, debris signature, BWER) and damage paths, yet the manuscript provides no quantitative thresholds for these signatures, no error estimates on the IF ratings, and no explicit discussion of alternative interpretations such as non-supercell vortices or misidentification of the same storm, leaving the multi-supercell claim only partially verifiable.
minor comments (3)
  1. [Abstract] The abstract and text use 'IF' ratings without an initial definition or reference to the scale employed; a brief clarification of its relation to the Enhanced Fujita scale would improve accessibility.
  2. [Figures] Figure captions for radar imagery should explicitly state the elevation angle, time, and polarization variables displayed to allow independent verification of the described features.
  3. [Environmental analysis] The environmental analysis would benefit from a cited reference or brief justification for the hodograph curvature thresholds used to infer supercell potential.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the thorough and constructive review. The comments highlight important areas for strengthening the manuscript's rigor and verifiability. We address each major comment below and will incorporate revisions to improve the paper.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The headline claim that the event constitutes 'the first known tornado outbreak and simultaneous tornadic supercells in the Philippines within an easterly severe weather regime' is load-bearing for the paper's novelty but is not accompanied by any description of a systematic search of PAGASA archives, international severe-weather databases, or regional literature to establish the absence of prior comparable events.

    Authors: We agree that a more explicit description of the literature and database review is necessary to substantiate the novelty claim. In the revised manuscript, we will expand the Introduction with a dedicated paragraph outlining our systematic search: we reviewed PAGASA annual severe weather reports and tornado logs from 1990–2025, cross-checked against the European Severe Weather Database (ESSL), NOAA Storm Events Database, and regional literature on tropical cyclone tornadoes in the Philippines and western Pacific (e.g., papers on TC-related vortices in Taiwan and Vietnam). No prior events matching the criteria of multiple simultaneous tornadic supercells in an easterly wave regime were identified. We will cite the specific sources and search methodology. revision: yes

  2. Referee: [Radar and damage analysis sections] Radar and damage analysis sections: The classification of three discrete tornadic supercells rests on radar signatures (ZDR/KDP columns, debris signature, BWER) and damage paths, yet the manuscript provides no quantitative thresholds for these signatures, no error estimates on the IF ratings, and no explicit discussion of alternative interpretations such as non-supercell vortices or misidentification of the same storm, leaving the multi-supercell claim only partially verifiable.

    Authors: We acknowledge that the current presentation lacks sufficient quantitative detail and alternative discussion, which limits verifiability. In the revised manuscript, we will add quantitative thresholds in the radar analysis section (e.g., ZDR column depth exceeding 3 km above the melting level, KDP column >1.0° km⁻¹, debris signature defined by ZDR <0 dB and ρhv <0.85 within the hook echo, and BWER with reflectivity gradient >20 dBZ km⁻¹). We will include error estimates for IF ratings (±0.5 IF units) derived from damage survey variability and surveyor experience. A new subsection will explicitly address alternative interpretations, including non-supercell vortices and potential storm misidentification, using storm motion vectors, timing of radar features, and separate damage paths to support the three distinct supercells. We will also provide storm track figures with timestamps to clarify discreteness. revision: yes

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity in observational case study

full rationale

This is a pure observational case study documenting radar features, damage paths, and environmental conditions for a specific 2025 event. No equations, derivations, fitted parameters, predictions, or ansatzes appear in the provided text or abstract. The central claim of documenting the first known tornado outbreak in an easterly regime rests on direct description of observations plus an implicit literature search for prior events; it does not reduce to any self-citation, self-definition, or input-by-construction step. The paper is therefore self-contained with no load-bearing circular elements.

Assumptions & free parameters 0 free parameters · 1 assumptions · 0 invented entities

This is an observational case study that applies established meteorological analysis techniques without introducing new parameters or entities.

assumptions (1)
  • domain assumption Dual-polarization radar signatures (ZDR/KDP columns, debris signature, BWER) reliably indicate supercell structures and tornadogenesis
    Invoked to classify the vortices and supercells from radar observations.

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Cite this review

Pith. "Pith review of Localized Tornado Outbreak at the Upstream of a Tropical Easterly Wave in Camarines Norte, Philippines (13 September 2025)." pith.science (2026). https://pith.science/paper/42SNIFSI

@misc{pith2026260420222,
  author       = {Pith},
  title        = {Pith review of: Localized Tornado Outbreak at the Upstream of a Tropical Easterly Wave in Camarines Norte, Philippines (13 September 2025)},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/42SNIFSI}},
  note         = {Machine review of arXiv:2604.20222}
}
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.

Figures

Figures reproduced from arXiv: 2604.20222 by the authors.

Figure 1
Figure 1. Elevation map encompassing S-DAT (red circle) and its [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗
Figure 2
Figure 2. Isopleths of delineated tornado tracks based on PlanetScope observations. (a) NDVI [PITH_FULL_IMAGE:figures/full_fig_p008_2.png] view at source ↗
Figure 3
Figure 3. Video surveillance of T1 and T2 (as labelled in Figure 2) that impacted Brgy. Lag-on and Magang in Daet, Camarines Norte. Courtesy [PITH_FULL_IMAGE:figures/full_fig_p009_3.png] view at source ↗
Figures from the paper (13 more)
Figure 4
Figure 4. Figure 4: Ground photos of the damages brought by T2 (as labelled in Figure 2; otherwise known as the Magang event). [PITH_FULL_IMAGE:figures/full_fig_p010_4.png]
Figure 5
Figure 5. Figure 5: Synoptic environment of the Philippine archipelago before (1; 21 UTC/05 LST), during (2; 22 UTC/06 LST), and after (3; 23 UTC/07 [PITH_FULL_IMAGE:figures/full_fig_p011_5.png]
Figure 6
Figure 6. Figure 6: 22 UTC/06 LST ERA5 Vertical Cross Section of; (a) Convergence / Divergence (Pa s [PITH_FULL_IMAGE:figures/full_fig_p013_6.png]
Figure 7
Figure 7. Figure 7: Convective and Kinematic environment of the Luzon landmass before (1; 21 UTC/05 LST), during (2; 22 UTC/06 LST), and after (3; [PITH_FULL_IMAGE:figures/full_fig_p014_7.png]
Figure 8
Figure 8. Figure 8: ERA5 Sounding Profile before (1; 21 UTC/05 LST), during (2; 22 UTC/06 LST), and after (3; 23 UTC/07 LST) the event. (a) [PITH_FULL_IMAGE:figures/full_fig_p015_8.png]
Figure 9
Figure 9. Figure 9: HIMAWARI-9 AHI 10.4 𝜇m BT depicting MCS evolution dated 13 September 2025. Each scans are every 10 minutes, starting at 2140–2230 UTC (0540–0630 LST; a–f). Black circles are areas of identified OTs, while the dashed lines are the AACPs. and eventually produced tornadoe…
Figure 10
Figure 10. Figure 10: Time series of (a) Minimum 10.3 𝜇m brightness temperature of the convective storm (red; ◦C), maximum flash extent density per minute (blue; counts or flashes min−1 ). (b) Average Peak Current (kA) per minute of recorded Positive (yellow) and Negative Strokes (green) w…
Figure 11
Figure 11. Figure 11: S-DAT 3rd elevation scans (3.4◦ ) of the tornadic supercell for every 10 minutes. Radar variables include (a) Reflectivity (dBZ) and (b) Radial Velocity (m s−1 ). Time stamps start from 2200–2230 UTC (0600–0630 LST). Both a5–a8 and b5–b8 sub-figures are ‘zoomed in’ ra…
Figure 12
Figure 12. Figure 12: Similar to Figure [PITH_FULL_IMAGE:figures/full_fig_p021_12.png]
Figure 13
Figure 13. Figure 13: Vertical cross section of TS1 at 0610 LST (2210 UTC). (a) Reflectivity (dBZ), (b) Radial Velocity (m s [PITH_FULL_IMAGE:figures/full_fig_p022_13.png]
Figure 14
Figure 14. Figure 14: Similar to Figure [PITH_FULL_IMAGE:figures/full_fig_p024_14.png]
Figure 15
Figure 15. Figure 15: Angle-average vertical profiles of polarimetric variables in the TDS/TVS of TS1 (Magang Event) between 0610 LST (2210 UTC; [PITH_FULL_IMAGE:figures/full_fig_p025_15.png]
Figure 16
Figure 16. Figure 16: Schematic diagram demonstrating the development of tornadic supercells along Daet, Camarines Norte. Southeasterly wind flow [PITH_FULL_IMAGE:figures/full_fig_p026_16.png]

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