According to Phung Tien Dung, head of the Hydrological Forecasting Division at the National Centre for Hydro-Meteorological Forecasting (NCHMF), the floods inundating Gia Lai, Dak Lak and Khanh Hoa are among the most unusual events recorded in many years.

“Several locations have reached or surpassed historic flood levels. Nha Trang has never experienced such deep and widespread inundation,” he said.

Dung noted that a comprehensive assessment of the underlying causes will require time to analyze rainfall and flood frequency, along with evaluating how socio-economic development has affected water flow, irrigation infrastructure, and flood-drainage capacity.

Rare conjunction of extreme weather systems

Truong Ba Kien, deputy director of the Centre for Meteorological and Climate Research, said the heavy rainfall stemmed from the unusual convergence of several atmospheric factors.

A strong early-season cold surge moved deep into central Vietnam and was deflected by the southern Truong Son Mountain Range into northeasterly and easterly winds, generating widespread rainfall. At the same time, moist onshore winds strengthened the rain, further intensified by a robust Pacific high-pressure system that created a broad wind-convergence zone.

Observations show that sea surface temperatures in the East Sea are currently 1–1.5°C above the long-term average, despite the cool season. Kien said the anomalously warm waters enabled northerly and easterly winds to carry more moisture, causing heavier rainfall when interacting with the local terrain.

He noted that similar wind-convergence patterns in previous years did not produce such intense rainfall because sea temperatures were lower.

The equatorial convective cloud band has also shifted northward in recent days, adding further instability and extending the duration of rainfall across the south-central region and the Central Highlands.

Experts warned that warming oceans and atmosphere driven by climate change are increasing both the frequency and severity of extreme rainfall events.

“Weather patterns once considered rare are now appearing more often,” Kien said.

Why floods keep rising and falling

Nguyen Van Huong, head of the Weather Forecasting Department at NCHMF, said the repeated rise-and-fall cycles of floodwaters in central Vietnam are being driven by successive bursts of easterly winds — the region’s classic rain-producing mechanism.

“Each surge of easterly winds brings a new round of rain and a new flood cycle. When rainfall temporarily eases, water levels drop. But once the winds strengthen again, rains intensify and floods rise rapidly,” he explained.

Rain is expected to continue until around November 20 before tapering off. However, another surge of easterly winds on November 23–24 may cause water levels to rise again from Da Nang to Khanh Hoa.

After weeks of persistent rain from late October to mid-November, soils in mountainous areas are now fully saturated, placing those regions at very high risk of flashfloods, landslides, and slope failures — even during dry weather.

Reservoirs near capacity require tighter monitoring

Hoang Duc Cuong, deputy director of the Hydro-Meteorological Administration, said early warnings were issued. However, with many reservoirs already near full capacity and rainfall varying sharply, forecasts must account for the discharge capacity of each reservoir.

Agencies are strengthening rainfall-monitoring networks, checking automatic weather stations, and preparing backup systems to ensure continuous data transmission.

Local meteorological stations have been advised to consider escalating risk levels, particularly for flashfloods and landslides. With the rainy season at its peak, experts caution that additional episodes of heavy rainfall are highly likely through the end of the year.

Politburo directs coordinated flood relief and recovery efforts in central Vietnam

VOV.VN - The Politburo and Secretariat have decided to set up five working groups, led by senior Party and State leaders, to continue inspecting, directing, and supervising flood recovery efforts in several central provinces.