Why Super Typhoon Ragasa intensified so rapidly and wreaked such damage

Typhoon Ragasa, locally known as Nando in the Philippines, formed over the western Pacific in mid-September and rapidly intensified into a Category 5-equivalent typhoon, fueled by unusually warm sea surface temperatures and low vertical wind shear that allowed sustained wind speeds of up to 265 km/h.

Its path over open waters without interruption by land enabled it to maintain and increase strength, making it one of the most powerful storms of the year.

Hong Kong experienced severe flooding and storm surges, with waves over three meters breaching coastal defenses. Streets and subway stations were submerged, and over 100 people were injured. The typhoon also disrupted air travel, forcing the city’s airport to close for more than a day.

Southern China, including Guangdong and Fujian provinces, faced widespread wind damage and flooding. Over 50,000 trees were uprooted, streets submerged, and tens of thousands of households lost electricity.

Authorities evacuated more than two million residents in anticipation of rising water levels. Ragasa’s trajectory placed densely populated coastal regions under the storm’s most intense quadrant, heightening its destructive impact.

Ragasa, one of 2025’s strongest storms, underwent unusually fast strengthening as it travelled over very warm waters with low wind shear and excellent upper-level ventilation.

The super typhoon moved over a broad swath of very warm ocean water — analyses and operational advisories cite sea-surface temperatures in the storm’s track around 29–30 °C, a level that supplies substantial heat and moisture to the cyclone’s core and supports deep convective bursts.

Multiple forecasting and analysis agencies flagged this unusually warm ocean strip as a primary energy source for Ragasa’s intensification.

Satellite and forecast analyses showed weak vertical wind shear during Ragasa’s intensification window, meaning winds at different altitudes did not tear the storm’s vertical structure apart.

At the same time, satellite imagery and operational blogs recorded robust upper-level outflow — air being evacuated efficiently from the storm top — allowing rising air to be replaced and the inner eyewall convection to strengthen without choking.

These two atmospheric features are repeatedly cited in the satellite-analysis and meteorological advisories as critical to the storm’s rapid consolidation.

Ragasa’s track kept it over open ocean for a prolonged period and was steered by a steady subtropical ridge, preventing early land interaction that would normally weaken a cyclone.

Forecasters noted that the storm’s steering environment kept it over the warm water window long enough for repeated cycles of eyewall intensification and to sustain very low central pressure.

This uninterrupted ocean phase was repeatedly highlighted in operational forecasts as a factor enabling the storm to reach and maintain extreme intensity.

While these oceanic and atmospheric factors explain why Ragasa became so strong, several local geographic and land-use conditions magnified the human and infrastructural toll once the storm’s rains and surge reached land.

In Taiwan, heavy rainfall contributed to the overflow of a barrier (landslide-formed) lake in Hualien County. The floodwaters inundated nearby villages, destroying homes and infrastructure, killing at least 14 people, and leaving more than 120 missing.

Landslides and swollen rivers complicated rescue efforts, illustrating how mountainous terrain can amplify storm damage.

Scientists have noted that warmer oceans increase the potential energy available to tropical cyclones, and 2025 has been among the warmer years for global sea surfaces; operational reports therefore routinely cite warm SSTs as a facilitating condition.

However, formal attribution of a single storm’s intensity to long-term climate change requires dedicated attribution studies; regional agencies and scientific commentators emphasize this distinction — observed warmth and ocean heat content are immediate drivers, while attribution to anthropogenic climate change is a separate scientific question that needs specific analysis.