Report on Super Typhoon Ragasa (2518)
Super Typhoon Ragasa (2518)
18 to 25 September 2025
Ragasa was the eleventh tropical cyclone affecting Hong Kong in 2025. Since Typhoon Wipha hit Hong Kong in July, Ragasa necessitated the issuance of the second Hurricane Signal No. 10 in the year during its passage, tying the previous record in 1964.
Ragasa formed as a tropical depression over the western North Pacific about 1 450 km east of Manila in the small hours of 18 September and moved generally west-northwestwards towards the Luzon Strait in the following three days. As the tropical cyclone heat potential was relatively high over the western North Pacific to the east of the Philippines, together with favourable upper-level divergence and weak vertical wind shear, Ragasa rapidly intensified into a super typhoon in the small hours on 21 September and attained its peak intensity that night, with an estimated maximum sustained wind of 230 km/h near its centre.
Ragasa adopted a westerly track across the Luzon Strait the next day. As its centre did not pass over major landmasses such as Luzon or Taiwan, its structure remained intact with extensive circulation and a clear, well‑defined eye as it entered the South China Sea. The maximum sustained wind near its centre remained at 230 km/h, making it the strongest tropical cyclone in the western North Pacific and the South China Sea region in 2025. It is also the second strongest tropical cyclone in the South China Sea since the Observatory’s records began in 1950, on par with Super Typhoons Saola in 2023 and Yagi in 2024. Ragasa turned to track west-northwestwards across the northern part of the South China Sea on 23 September and edged closer to the coast of Guangdong the next morning. Due to favourable atmospheric and oceanic conditions in the South China Sea, Ragasa maintained its super typhoon intensity throughout. It made landfall near Yangjiang of Guangdong on the afternoon of 24 September and then weakened rapidly. It moved across the coast of Guangxi the next day and finally degenerated into an area of low pressure over the northern part of Vietnam that night.
According to press reports, Ragasa brought torrential rain and squalls to the northern part of the Philippines, causing at least 13 deaths, one missing and 17 injuries. More than 910 000 people were affected and economic loss exceeded PHP 37 million. Under the influence of the outer rainbands of Ragasa, torrential rain caused the overflow of the Matai'an barrier lake in Taiwan, flooding three downstream townships and resulting in 19 deaths, five missing persons, and 157 injuries. Water and electricity supplies to more than 4 300 and 17 000 households were disrupted respectively in Taiwan. Economic loss exceeded USD 19 million. More than 2.21 million people in Zhejiang, Fujian, Guangdong, Guangxi, Hainan and Yunnan were also affected. Over 53 000 trees were damaged in Yangjiang of Guangdong. Maximum gust of 234 km/h was recorded on Shangchuan Dao in Taishan, the highest on record by a national meteorological station in Guangdong. Besides, eight people were injured when Ragasa affected Macau. Electricity supply to about 16 000 households was disrupted. There were also 259 incident reports. At least 206 flights were cancelled at the Macau International Airport.
Due to Ragasa’s extensive circulation and relatively fast movement, the Standby Signal No. 1 was issued at 12:20 p.m. on 22 September, when Ragasa was about 870 km east-southeast of Hong Kong. Local winds were moderate to fresh northwesterlies that afternoon. With Ragasa gradually edging closer to the coast of Guangdong, the No. 3 Strong Wind Signal was issued at 9:40 p.m. that night, when Ragasa was about 700 km east-southeast of Hong Kong. Local winds strengthened gradually the next morning, with fresh north to northwesterlies, strong offshore and on high ground.
Since Ragasa was expected to maintain super typhoon intensity as it approached the vicinity of the Pearl River Estuary, the No. 8 Northwest Gale or Storm Signal was issued at 2:20 p.m. on 23 September when Ragasa was about 370 km southeast of Hong Kong. Local winds further strengthened that night, with strong to gale force northerlies. With Ragasa further approaching Hong Kong with super typhoon intensity, its hurricane force winds were expected to edge close to the territory. The Increasing Gale or Storm Signal No. 9 was issued at 1:40 a.m. on 24 September when Ragasa was about 150 km south-southeast of Hong Kong. Local wind strength increased rapidly afterwards, with gale to storm force north to northeasterlies generally over the territory. Since the outer eyewall of Ragasa and its associated hurricane force winds were expected to lash Hong Kong, the Hurricane Signal No. 10 was issued at 2:40 a.m. that day when Ragasa was about 140 km south-southeast of Hong Kong. The territory was persistently battered by the outer eyewall of Ragasa in the morning, with storm to hurricane force east to northeasterlies affecting many places. Ragasa came closest to Hong Kong at around 6 a.m. that morning, when its centre was located at about 120 km south of Hong Kong. It was the furthest tropical cyclone from Hong Kong since 1946 that necessitated the issuance of the Hurricane Signal No. 10.
With Ragasa skirting past southwest of Hong Kong, local winds veered to east to southeasterlies gradually later in the morning. Ragasa departed from Hong Kong gradually. When hurricane force winds no longer posed threat to the territory, the No. 8 Southeast Gale or Storm Signal was issued at 1:20 p.m. on 24 September to replace the Hurricane Signal No. 10. The Signal No.10 was in force for 10 hours and 40 minutes, second only to the record of 11 hours set during the passage of Typhoon York in 1999. As Ragasa weakened and continued to depart from Hong Kong, local winds continued to weaken. The No. 3 Strong Wind Signal and the No. 1 Standby Signal were issued at 8:20 p.m. that night and at 8:20 a.m. the next day respectively, and all tropical cyclone warning signals were cancelled at 11:20 a.m. on 25 September. However, under the combined effect of the ridge of high pressure along the coast of southeastern China and Ragasa, strong winds continued to affect offshore and high ground in Hong Kong. The Strong Monsoon Signal was issued shortly thereafter and lasted till 7:45 a.m. on 26 September.
During the passage of Ragasa over the northern part of the South China Sea, the Observatory cooperated with the Government Flying Service and deployed dropsondes in the northwest quadrant of Ragasa on the morning of 23 September. Near-surface hurricane force winds were recorded at a distance of 120 km from its centre, indicating that the area of hurricane force winds of Ragasa was extensive. The fixed-wing aircraft dispatched by the Government Flying Service flew through the eye of Ragasa, capturing its internal structure, including its eye and eyewall (Figure 5). Radar imagery from that night to the next morning captured the double eyewall structure of Ragasa (Figure 6a). With Ragasa edging closer to the territory, its eyewalls contracted gradually due to eyewall replacement, but the convection near the eyewalls remained intense. During the passage of Ragasa about 120 km south of Hong Kong on the morning of September 24, its outer eyewall persistently battered the southern part of Hong Kong (Figure 6b).
The storm to hurricane force winds of Ragasa affected many places of Hong Kong on the morning of 24 September. Maximum hourly mean winds of 137, 132 and 113 km/h and gusts of 212, 166 and 167 km/h were recorded at Ngong Ping, Waglan Island and Cheung Chau respectively. During the passage of Ragasa, the overall wind strength in Hong Kong was similar to those of Hato in 2017, Saola in 2023 and Wipha in 2025, but weaker than that of Mangkhut in 2018 (Table 2).
As the approach of Ragasa coincided with the astronomical high tide, the storm surge induced by Ragasa resulted in rising water levels in many parts of the territory by approximately 1.5 to 2.0 m above normal. The sea level at Quarry Bay in Victoria Harbour rose to a maximum of 3.40 m (above chart datum), close to the level when Hato hit Hong Kong in 2017. A maximum sea level of 3.77 m (above chart datum) was recorded at Tsim Bei Tsui and a maximum storm surge of 2.10 m (above astronomical tide) was recorded at Tai Po Kau. The lowest instantaneous mean sea-level pressures recorded at some selected stations are as follows:
| Station | Lowest instantaneous mean sea-level pressure (hPa) |
Date/Month | Time |
|---|---|---|---|
| Hong Kong Observatory Headquarters | 985.4 | 24/9 | 4:39 a.m. |
| Hong Kong International Airport | 985.1 | 24/9 | 6:56 a.m. |
| Cheung Chau | 982.9 | 24/9 | 5:18 a.m. |
| King’s Park | 985.4 | 24/9 | 4:45 a.m. |
| Lau Fau Shan | 987.6 | 24/9 | 5:08 a.m. |
| Peng Chau | 984.2 | 24/9 | 4:53 a.m. |
| Sha Tin | 987.8 | 24/9 | 4:50 a.m. |
| Sheung Shui | 987.7 | 24/9 | 4:59 a.m. |
| Ta Kwu Ling | 988.5 | 24/9 | 5:00 a.m. |
| Tai Po (Yuen Chau Tsai Park) | 989.1 | 24/9 | 4:58 a.m. |
| Waglan Island | 984.9 | 24/9 | 2:12 a.m. |
Locally, it was very hot with sunny periods on 22 September under the influence of Ragasa’s outer subsiding air. With the approach of the intense rainbands associated with Ragasa, the weather deteriorated rapidly with squally showers later the next afternoon. The weather was persistently adverse with frequent heavy squally showers on 24 September, with more than 200 millimetres of rainfall generally recorded over the territory. Under the influence of the outer rainbands associated with Ragasa, there were still a few showers and isolated thunderstorms on 25 September.
During the passage of Ragasa, at least 101 people were injured in Hong Kong. A woman and her son were swept away by swells at the waterfront of Chai Wan and were later rescued. Locally, there were at least 5 062 reports of fallen trees, 24 reports of flooding and five reports of landslides. There were more than 1 600 road incident reports, including blockage of roads due to fallen trees, flooding or landslides. There were also 25 incident reports related to loosened or damaged signboards and scaffoldings. More than 700 flights were cancelled at the Hong Kong International Airport. There were at least 16 reports of marine incident, including minor vessel collisions, vessels dragging anchor and vessels crashing into the shore.
The hurricane force winds, storm surge, overtopping waves and rainstorm associated with Ragasa caused severe damage in various districts of Hong Kong. The passage of Ragasa resulted in fallen trees, damaged scaffolding and buildings in many parts of the territory. A tree of about 30 m tall collapsed and a 20 m by 30 m exterior scaffolding of a building was damaged in Ho Man Tin. The wall of a primary school collapsed and the wall of a detached house was damaged by a fallen tree in Kowloon Tong. The glass curtain wall of a building in Tsim Sha Tsui and the exterior wall tiles of a residential building in Sham Tseng were damaged. The canopy of an amphitheatre in Sha Tin was damaged. A construction site container in Tseung Kwan O was blown into the sea by high winds. Storm surge induced by Ragasa caused flooding in coastal and low-lying areas such as Tai O, Sam Ka Tsuen in Lei Yue Mun and Kar Wo Lei in Tuen Mun. Footpaths and subways near the Shing Mun River in Sha Tin and the Lam Tsuen River in Tai Po were flooded. Ragasa’s fierce winds also triggered overtopping waves, with rough waves crashing into coastal areas such as Chai Wan, Cheung Chau, Aberdeen and Tseung Kwan O South, causing flooding and damage to coastal facilities in many places. Seawater crashed into a hotel in Aberdeen, shattering its glass doors and flooding its lobby. The Tseung Kwan O Waterfront Park and Children's Playground were flooded. The public facilities at the Waterfront Promenade were severely damaged, with paving blocks damaged and cycle tracks flooded. Seawater surged into several restaurants, shattering the glass doors and leaving scattered items on the ground. Affected by the heavy rain of Ragasa, there were landslides in Sai Ying Pun, Stanley, Tai Po and Tuen Mun. A sunflower field in Yuen Long was flooded. The winds and waves brought by Ragasa caused several vessels colliding with the shore railings off the coast in Hung Hom and To Kwa Wan. Mariculture rafts and facilities in Lantau Island were also damaged.