Tropical Depression Mun (1904)
2 to 4 July 2019

Mun was the first tropical cyclone necessitating the issuance of tropical cyclone warning signal by the Hong Kong Observatory in 2019.

Mun formed as a tropical depression over the northern part of the South China Sea about 240 km southeast of Haikou on the afternoon of 2 July and moved generally westward. After moving across Hainan Island on the morning of 3 July, Mun entered Beibu Wan and slightly intensified, reaching its peak intensity with an estimated sustained wind of 55 km/h near its centre. Moving northwestwards across Beibu Wan, Mun weakened into an area of low pressure over the northern part of Vietnam on the morning of 4 July.

After the formation of Mun about 440 km south-southwest of Hong Kong on 2 July, the Hong Kong Observatory issued the Standby Signal No. 1 at 4:15 p.m. It was also closest to Hong Kong at that time. At the Observatory Headquarters, the lowest instantaneous mean sea-level pressure of 1000.3 hPa was recorded at 4:39 p.m. that day. Local winds were generally moderate to fresh east to southeasterlies during that night, occasionally strong offshore and on high ground. As the threat of Mun to Hong Kong diminished, all tropical cyclone warning signals were cancelled at 5:40 a.m. on 3 July.

Under the influence of Mun, a maximum sea level (above chart datum) of 2.07 m and a maximum storm surge of 0.38 m (above astronomical tide) were recorded at Tsim Bei Tsui.

Under the influence of rainbands associated with Mun, there were occasional heavy squally showers and thunderstorms on 2 and 3 July. More than 80 millimetres of rainfall were generally recorded over the territory during these two days, and rainfall even exceeded 120 millimetres over Lantau Island and the eastern part of Hong Kong.

Mun did not cause any significant damage in Hong Kong. According to press report, Mun disrupted sea, land, air transportation in Hainan Island.