Key Highlights
- Storm Nokaen (locally Ada) is expected to dump 100‑200 mm of rain over southern Luzon this weekend.
- Intense precipitation may mobilise recent volcanic deposits on Mayon’s slopes, creating fast‑moving mudflows (lahars).
- Phivolcs warns that lahars could be hot, travel downstream, and threaten evacuation centres, roads, and coastal zones.
- Thousands of residents already displaced by volcanic unrest face heightened risk of burial, impact by boulders, and washouts.
Detailed Insights
Tropical Storm Nokaen, the first cyclonic system of 2026 to strike the Philippines, is tracking northward across the Philippine Sea at a sluggish pace. PAGASA reports sustained winds near 65 km h⁻¹ with gusts up to 80 km h⁻¹. Its rainband will sweep across the eastern side of southern Luzon, delivering widespread precipitation over the weekend.
Mayon Volcano, an iconic stratovolcano in Albay, has been in a state of unrest since the start of the year. Successive eruptions have left abundant loose tephra, ash, and fragmented rock on its flanks. When the forecasted rainfall interacts with this unconsolidated material, the mixture can rapidly transform into lahars—dense, volcanic mudflows that follow river valleys and drainage networks.
According to the Philippine Institute of Volcanology and Seismology (Phivolcs), rainfall totals between 100 mm and 200 mm are sufficient to trigger both fresh and “syn‑eruption” lahars, the latter incorporating newly deposited pyroclastic debris. Some of these flows may retain elevated temperatures, posing burn hazards in addition to mechanical destruction.
The downstream impact zone includes populated settlements, agricultural fields, and infrastructure extending to the eastern coastline. Potential effects comprise inundation, burial of structures, collision with boulders, and washing out of bridges and roads. The already strained evacuation centres could become overcrowded, complicating rescue and relief operations.
Key Concepts
- Lahar: A volcanic mudflow generated when water—usually from heavy rain—mixes with loose volcanic ash, rock fragments, and debris, creating a fast‑moving slurry.
- Syn‑eruption lahar: A lahar that incorporates fresh pyroclastic material expelled during an ongoing volcanic eruption.
- Phivolcs: The Philippine Institute of Volcanology and Seismology, the government agency responsible for monitoring volcanic and seismic activity.
- Pyroclastic deposit: Accumulations of ash, pumice, and fragmented rock ejected during volcanic explosions.