Tropical Storm Nongfa Batters Vietnam, Philippines After South China Sea Trek
Tropical Storm Nongfa was a short-lived cyclone that crossed the South China Sea in late August 2025, producing wide regional weather effects across East Asia and Southeast Asia. The storm formed on August 27, strengthened into a tropical storm on August 29, and reached peak intensity before making landfall in central Vietnam on August 30. Nongfa affected southern China, the Philippines, Vietnam, and Thailand through heavy rainfall, gusty winds, and enhanced monsoon activity. The cyclone weakened over mainland Southeast Asia and dissipated on August 31, less than four days after formation.
Over the South China Sea: Nongfa’s Rapid Rise from Disturbance to Storm
Nongfa originated from a tropical disturbance over the western South China Sea on August 27, 2025. The system initially developed as a weak tropical depression near 14.8°N, 116.8°E, with a central pressure of 1002 hPa. During the following two days, the circulation gradually organized while moving westward across the basin.
The storm received the name Nongfa after strengthening within the regional tropical cyclone warning framework. The name was provided by Laos and means “blue lake” or “blue water”; it was not created by the China Meteorological Administration. The naming followed the established rotating list used for tropical cyclones in the western North Pacific and South China Sea.
Nongfa strengthened quickly on August 29 while moving toward the northern South China Sea. At 06:00 UTC that day, the system reached tropical storm intensity with maximum sustained winds of 18 meters per second and a central pressure of 998 hPa. The storm continued to organize as it approached the coastal waters near Vietnam.
Satellite imagery showed that Nongfa maintained an asymmetric structure throughout its lifetime. The strongest convection remained concentrated mainly on the southern and eastern sides of the circulation, while the northern and western areas were less active. The storm’s compact center belied a much broader rain shield, allowing rainfall impacts to extend far from the center of circulation.
The uneven structure also determined where the heaviest rain and strongest winds fell. The storm’s strongest wind field remained limited near the core, while moisture transport and outer rain bands affected areas hundreds of kilometres away from the storm centre.
Crossing Waters Near China: The Track That Spread Rainfall Beyond the Core
Nongfa followed a westward path across the South China Sea after formation, moving from offshore waters east of Vietnam toward the northern part of the basin. The storm maintained a forward speed of around 25 to 30 kilometres per hour, reducing the time available for significant strengthening while allowing its circulation to move across a broad region.
On August 29, Nongfa passed south of Hainan Island and continued toward the coast of Vietnam. Although the storm did not make a direct landfall in mainland China, its outer circulation affected southern coastal areas with increased cloud cover, rain showers, and thunderstorms.
The rainfall and moisture transport affected areas hundreds of kilometres from its centre. This pattern was especially important because tropical cyclone impacts are often determined by the size of the rain field rather than only the location of the strongest winds.
In Hong Kong, authorities monitored Nongfa through the local tropical cyclone warning system. The Hong Kong Observatory issued the Standby Signal No. 1, which is the lowest level in Hong Kong’s five-stage tropical cyclone warning system that includes Signals 1, 3, 8, 9, and 10. The signal indicated that the storm was close enough to bring potential weather changes while remaining outside the territory’s strongest impact zone.
The Philippines also monitored the system through its local warning framework. PAGASA referred to the storm as Bagyong Jacinto, the Philippine domestic name assigned to Nongfa during its period of influence over the Philippine Area of Responsibility. Rainfall associated with the storm and the southwest monsoon affected parts of the country before Nongfa moved farther west across the South China Sea.
Peak Strength and Vietnam Landfall: Nongfa’s Final Push Before Dissipation
Nongfa reached its strongest stage at 00:00 UTC on August 30, 2025. At that time, the storm was located near 17.7°N, 108.1°E, with maximum sustained winds of 20.6 meters per second, equivalent to 74 kilometres per hour, and a minimum central pressure of 996 hPa.
The storm maintained tropical storm intensity as it moved toward central Vietnam. Its structure remained asymmetric, preventing the development of a stronger and more organized circulation. The strongest winds stayed concentrated near the storm centre, while the wider circulation continued to produce heavy rainfall.
Nongfa made landfall in central Vietnam on August 30. Vietnamese authorities classified the system as Storm No. 6 of the 2025 season, with monitoring focused on heavy rain, flooding risks, and strong winds in affected provinces.
The main impact from Nongfa in Vietnam came from rainfall rather than extreme wind damage. Coastal and inland areas experienced periods of heavy precipitation as the storm crossed the country, with authorities maintaining warnings for flooding and landslides in vulnerable locations.
After moving inland, Nongfa weakened rapidly. By 18:00 UTC on August 30, the system had weakened into a tropical depression near northern Laos and Thailand. The circulation dissipated at 06:00 UTC on August 31 near 17.5°N, 100.1°E.
Regional Footprint: Nongfa’s Rain and Wind Lash Philippines, Vietnam, Thailand
Nongfa affected several countries despite remaining below typhoon strength during its entire lifetime. In the Philippines, the combination of Bagyong Jacinto and southwest monsoon activity brought heavy rain to affected communities. More than 250,000 people were reported affected during the period linked to the storm and monsoon conditions, with more than 470 houses damaged.
Vietnam experienced the most direct effects because Nongfa crossed the country after landfall. Heavy rainfall affected central provinces, while disaster agencies monitored rivers, mountain areas, and flood-prone communities. The storm’s passage added another period of rainfall stress during an active monsoon season.
Thailand also received rainfall from Nongfa’s weakening circulation after the storm crossed into mainland Southeast Asia. The remnants continued producing rain over northern areas before the system fully dissipated.
Nongfa’s complete meteorological record lasted from August 27 to August 31, 2025. The storm formed at 1002 hPa, reached a minimum pressure of 996 hPa, achieved maximum sustained winds of 20.6 meters per second, and completed its track from the South China Sea to northern Thailand within four days.