TROPICAL CYCLONES IN 2013

Utor was the fifth tropical cyclone necessitating the issuance of tropical cyclone warning signals by the Hong Kong Observatory in 2013. It was also the first necessitating the issuance of No. 8 Gale or Storm Signal in the year.

Utor formed as a tropical depression over the western North Pacific about 1 350 km east of Manila on 9 August and moved westwards. Utor intensified into a tropical storm in the small hours on the next day. It continued to intensify and became a typhoon while moving along a west-northwesterly track during the day. Utor developed into a severe typhoon in the morning on 11 August and strengthened further into a super typhoon over the sea areas east of Luzon that evening, reaching its peak intensity with estimated sustained winds of 195 km/h near its centre. It crossed Luzon in the small hours on 12 August and weakened into a severe typhoon before entering the South China Sea in the morning. Utor gradually took on a northwesterly track the next day over the northern part of the South China Sea to the south of Hong Kong. It approached the coast of western Guangdong and weakened into a typhoon in the afternoon on 14 August. At 2 p.m., the mean sea-level pressure at Yangjiang fell to 972.9 hPa. Utor then made landfall near Yangjiang and moved across the coast of western Guangdong that evening, weakening into a severe tropical storm at night. It slowed down and turned northwards across Guangxi on 15 August. Utor weakened into a tropical storm in the morning and a tropical depression that afternoon. It finally dissipated over Guangxi the next day.

According to press reports, at least two people were killed and 46 fishermen were missing in the Philippines. Utor also caused a number of landslides. Over 600 houses were damaged and electricity supply to more than 1,000 households interrupted. Three people were killed and five went missing at Maoming and Yangjiang in Guangdong during the passage of Utor, with direct economic losses exceeding 1 800 million RMB. In addition, two people were also killed in Guangxi according to reports.

The Hong Kong Observatory issued the Standby Signal No. 1 at 4:05 p.m. on 12 August when Utor was about 710 km southeast of the territory. As Utor edged steadily towards the coast of western Guangdong, local winds strengthened gradually the next day. The Strong Wind Signal No. 3 was issued at 4:40 a.m. when Utor was about 490 km south-southeast of Hong Kong. Local winds became strong east to northeasterlies in the afternoon, occasionally reaching gale force offshore and on high ground. As Utor continued to move closer to Hong Kong, the No. 8 SE Gale or Storm Signal was issued at 1:40 a.m. on 14 August when Utor was about 310 km to the south-southwest. Local winds became strong to gale force east to southeasterlies during the morning, occasionally reaching storm force on high ground. Utor was closest to Hong Kong around 1 p.m. that day as it passed by about 240 km to the west-southwest. The Strong Wind Signal No.3 was issued at 1:40 p.m. as Utor started to weaken. While gale force winds continued to affect the waters and high ground over the southwestern part of Hong Kong, local winds gradually subsided. As Utor moved further away and weakened, the Standby Signal No.1 was issued at 1:40 a.m. on 15 August. Local winds remained strong over the offshore waters to the south and west of Hong Kong during the morning as Utor moved slowly and its rainbands continued to affect the Pearl River Estuary. All tropical cyclone warning signals were cancelled at 4:40 p.m. as local winds further subsided.

During the passage of Utor, a maximum hourly mean wind of 75 km/h was recorded at Waglan Island, while maximum gusts of 104 km/h were recorded at Cheung Chau. A maximum sea level (above chart datum) of 2.76 m was recorded at Tsim Bei Tsui, while a maximum storm surge of 0.63 m was recorded at Tai Po Kau. The lowest instantaneous mean sea-level pressures recorded at some selected stations are as follows:-

The weather in Hong Kong was fine and very hot on 12 August, with a maximum temperature of 34.9 degrees at the Hong Kong Observatory, the highest so far this year. Under the influence of the rainbands of Utor, the weather became cloudy to overcast with heavy squally showers and a few thunderstorms in the next couple of days. The rainbands of Utor continued to bring showers to Hong Kong on 15 August. More than 100 millimetres of rainfall were recorded over parts of the territory during these four days.

In Hong Kong, nine people were injured during the passage of Utor. Two people were rescued and one went missing when diving in the sea areas off Tai Po. There were 415 reports of fallen trees, six reports of minor flooding, as well as a number of reports of collapsed scaffolding or signboards. A glass panel fell from a commercial building in Chai Wan, hitting two private vehicles. Satellite antennas were toppled by winds in Kowloon City and To Kwa Wan, damaging a street lamp and three motorcycles. At the Hong Kong International Airport, 148 flights were cancelled, 663 flights delayed and 32 flights were diverted due to adverse weather. A Guangdong-bound cargo vessel sank in the waters about 80 kilometres southwest of Hong Kong. All 21 crew members were rescued.

Information on the maximum wind, period of strong and gale force winds, daily rainfall and maximum sea level reached in Hong Kong during the passage of Utor is given in Tables 3.5.1 - 3.5.4 respectively. Figures 3.5.1 and 3.5.2 show respectively the track of Utor and the rainfall distribution for Hong Kong. Figure 3.5.3 shows the winds recorded at various stations in Hong Kong. Charts in figures 3.5.4 show the time traces of wind speed and mean sea-level pressure recorded at Cheung Chau. Figures 3.5.5 and 3.5.6 show respectively a satellite imagery of Utor and the radar imagery of the outer rainbands of Utor.