TROPICAL CYCLONES IN 2016

3.7 Tropical Storm Aere (1619): 5 – 14 October 2016

Aere was the seventh tropical cyclone necessitating the issuance of tropical cyclone warning signals by the Hong Kong Observatory in 2016.

Aere formed as a tropical depression over the western North Pacific about 900 km east of Dongsha on the afternoon of 5 October. Moving west to west-northwestwards, it moved across the Luzon Strait and entered the northeastern part of the South China Sea the next day while intensifying into a tropical storm. After crossing the sea areas south of Dongsha in the early morning on 7 October, Aere slowed down and drifted northwards during the day, reaching its peak intensity in the afternoon with an estimated sustained wind of 85 km/h near its centre. Aere moved northeastwards slowly on 8 October and became almost stationary the next day as it weakened gradually.

Aere picked up speed and turned to move southwestwards on 10 October, degenerating into an area of low pressure near Dongsha that night. However, its remnant low pressure area continued to track to the southwest towards the sea areas around Xisha over the next couple of days. It re-intensified into a tropical depression south of Hainan Island on the morning of 13 October and turned westwards. After making landfall over the central part of Vietnam early next morning, Aere weakened into an area of low pressure before dissipating further inland.

According to press reports, the outer circulation of Aere brought heavy rain to southern Taiwan and caused flooding in some areas. Land and sea transportation services were affected.

In Hong Kong, the Standby Signal No. 1 was issued at 8:40 p.m. on 6 October when Aere was about 420 km east-southeast of Hong Kong. Local winds were generally moderate to fresh northerly on 7 and 8 October, occasionally reaching strong force on high ground. At the Observatory Headquarters, the lowest instantaneous mean sea-level pressure of 1005.2 hPa was recorded at 3:24 p.m on 7 October. Aere came closest to the territory around 8 p.m. that evening, passing at a distance of about 260 km to the east-southeast of Hong Kong. As the northeast monsoon reached the coastal area of Guangdong early in the early morning on 9 October, Aere started to weaken and turn southwestwards away from Hong Kong the next day. With the threat of Aere to Hong Kong diminishing, all tropical cyclone warning signals were cancelled at 3:45 a.m. on 9 October.

During the passage of Aere, a maximum sea level (above chart datum) of 2.54 m was recorded at Tsim Bei Tsui, while a maximum storm surge of 0.29 m (above astronomical tide) was recorded at Tai Po Kau.

With its rather small circulation, Aere had no major impact on Hong Kong and brought no significant damage. Locally, there were only a few squally showers on 7 and 8 October. Under the influence of the northeast monsoon, the weather was relatively cool and dry on 9 October.

Information on the maximum wind, daily rainfall and maximum sea level reached in Hong Kong during the passage of Aere is given in Tables 3.7.1 - 3.7.3 respectively. Figures 3.7.1 - 3.7.4 show respectively the track of Aere, the rainfall distribution for Hong Kong, satellite imageries and a related radar imagery of Aere.