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Typhoon Sam (9910)19 - 23 August 1999

        A tropical depression named Sam developed about 680 km east-northeast of Manila on 19 August. Tracking west-northwestwards over the Pacific, Sam intensified into a tropical storm that night. It then swept across the northern part of Luzon the next day. The passage of Sam caused one death and nine injuries in the Philippines. More than 4 000 people had to be evacuated.

        Upon entering the South China Sea, Sam intensified into a severe tropical storm on 21 August. Moving northwestwards towards the coast of Guangdong, Sam attained typhoon strength on the late morning of 22 August. Weakening rapidly into a severe tropical storm, Sam made landfall over Hong Kong that evening and headed towards the Zhujiang Estuary.

        After crossing the Zhujiang Estuary, Sam weakened gradually into an area of low pressure over inland Guangdong on 23 August. In Guangdong, at least five persons were killed and 100 were injured. Sam also caused serious traffic disruption and the closure of several airports in Guangdong. Direct economic losses were put at 150 million RMB.

        In Hong Kong the Standby Signal No. 1 was hoisted at 4.15 p.m. on 20 August when Sam was about 800 km to the east-southeast. The weather on 21 August was fine and very hot with haze at first. The maximum temperature of 35.1oC recorded at the afternoon of 21 August was the highest since 1990.

        Showers began to set in from the late afternoon of 21 August as Hong Kong came under the influence of Sam's outer rainbands. With Sam moving closer to Hong Kong and winds becoming strong offshore and on high ground, the Strong Wind Signal No. 3 was hoisted at 2.30 a.m. on 22 August. Sam attained typhoon strength later that morning and local winds reached gale force at Waglan Island and Cheung Chau. The No. 8 NORTHWEST Gale or Storm Signal was hoisted at 12.30 p.m. Sam was the third tropical cyclone necessitating the hoisting of No. 8 or higher signals in the year. The last time that No. 8 or higher signals had to be hoisted on three separate occasions between January and August was in 1971.

        After weakening into a severe tropical storm, Sam made landfall over the eastern part of Sai Kung at around 6 p.m. on 22 August. Sam was closest to the Hong Kong Observatory Headquarters at around 6.15 p.m. when it was about 25 km to the northeast. Following landfall Sam traversed the northeastern part of the New Territories at a speed of about 25 km/h and crossed into Shenzhen. During the passage of Sam, the lowest instantaneous mean sea-level pressures recorded at selected stations were as follows :


Lowest instantaneous
mean sea-level pressure 

Hong Kong Observatory Headquarters

981.9 hPa                          

Ta Kwu Ling

983.5 hPa                          

Sha Tin

982.3 hPa                          

Waglan Island

979.0 hPa                          

        During the passage of Sam, a maximum hourly wind of 52 km/h and a maximum gust of 115 km/h were recorded at Tap Mun on 22 August. At Waglan, a maximum hourly wind of 96 km/h and a maximum gust of 148 km/h were recorded. As Sam moved into Shenzhen and entered the Zhujiang Estuary that night, local winds began to turn southwesterly and the No. 8 SOUTHWEST Gale or Storm Signal was hoisted at 8.10 p.m. With Sam moving gradually away and weakening into a tropical storm, the No. 8 Signal was replaced by the Strong Wind Signal No. 3 at 3.50 a.m. on 23 August. Sam weakened further into an area of low pressure that night and all tropical cyclone warning signals were lowered at 9.00 p.m.

        The southwesterly winds trailing in the wake of Sam brought heavy rain to Hong Kong. Gusts occasionally reached gale force at that time. The Black Rainstorm Warning Signal was issued at 6.13 a.m. on 23 August and was replaced by the Amber Rainstorm Warning Signal at noon. The Black Rainstorm Warning Signal was raised again on 24 August and in force between 4.35 a.m. and 10.00 a.m. The tropical cyclone rainfall (defined as the total rainfall recorded at the Hong Kong Observatory from the time when a tropical cyclone was centred within 600 km of Hong Kong to 72 hours after the tropical cyclone has dissipated or moved outside 600 km of Hong Kong) brought by Sam amounted to 616.5 mm. This exceeded the previous record of 597.0 mm caused by a tropical cyclone in 1926 and made Sam the wettest tropical cyclone ever to affect Hong Kong since records began in 1884.

        During the passage of Sam, an accident occurred while an aircraft was trying to land at the airport at Chek Lap Kok in the evening of 22 August. Three passengers were killed and more than 200 injured in the incident. Over 360 other flights were delayed or cancelled in the next few days. Ferry services to Cheung Chau, Peng Chau and Mui Wo were suspended in the afternoon of 22 August and some 300 passengers living in these outlying islands were affected.

        Locally, numerous trees toppled and signboards collapsed in gales and strong winds. Eight cases of traffic accidents resulting from the inclement weather were reported. Seas were very rough and four surfers were reported missing near Tai Mei Tuk but were found later. More than 100 people suffered minor injuries in various storm related accidents.

        The heavy rain resulted in about 310 cases of flooding and 200 cases of landslides in various part of Hong Kong. The most severe flooding occurred in the northern New Territories where floodwaters two metres in depth were reported. Some villagers were trapped on rooftops and in trees and had to be rescued. More than 200 residents of Tin Ping Shan, Mai Po, Ta Kwu Ling, Ping Kong, Sham Tseng San Tsuen were forced to flee their homes.

        In Sham Tseng San Tsuen, one man was buried alive and 28 others were injured in a landslide on 23 August. In Tin Wan in Aberdeen, 30 stores were swamped by mudflow. Many roads on Hong Kong Island were also forced to close due to landslides. On Lantau Island, landslides also caused the closure of Tung Chung Road and South Lantau Road. Bus services on Lantau Island were almost paralyzed on 24 August. In Kowloon, Shekipmei Estate was threatened by possible landslides and over 700 residents had to be evacuated on 25 and 26 August.

Last revision date: <19 Dec 2012>