The Weather of June 2000

    June 2000 was warmer and rainier than usual. The mean, mean maximum and mean minimum temperatures were all 0.5 degrees above normal. The monthly maximum temperature of 34.2 degrees was the fourth highest for June. The monthly total rainfall was 443.3 millimetres, 18 per cent above the normal figure. The accumulated rainfall since 1 January amounted to 1 338.1 millimetres, 35 per cent above the normal figure of 992.5 millimetres for the same period. The mean relative humidity of only 78 per cent was equal to the lowest record for June set in 1967 and 1988.

    The Black Rainstorm Warning Signal was issued on 12 June when 84.3 millimetres of rainfall were recorded between 5 a.m. and 6 a.m. This was the fourth highest hourly rainfall for June. The rapid formation of a tropical depression over the waters just to the south of Lantau Island on 18 June necessitated the direct hoisting of the Strong Wind Signal No. 3. It was lowered four and a half hours later, producing the shortest duration on record for the hoisting of Tropical Cyclone Warning Signals.

    With the subtropical ridge of high pressure persisting over the south China coast, the fine and hot spell which began at the end of May continued for the first few days of the month. With abundant sunshine and light winds, it was very hot with a maximum temperature of 34.2 degrees on 5 June, the highest in the month. Temperatures rose to over 36 degrees at parts of the New Territories.

    Southwesterly winds brought a few isolated thundery showers on the morning of 7 June but it again turned fine and hot in the afternoon. There were sunny periods and a few showers the next day.

    The weather became cloudy with scattered showers on 9 June but gave way to sunny periods over the next couple of days.

    A trough of low pressure crossed the south China coast on 12 June, bringing heavy thundery showers to the region. Between 100 and 150 millimetres of rainfall were recorded generally over Hong Kong Island and Kowloon in the morning. Three cases of landslip and 28 cases of flooding were reported. A commercial building experienced a power cut when its ground-floor meter room was flooded. Northerly winds behind the trough brought unseasonably cool weather to Hong Kong and it remained cool for the next couple of days. Temperatures dropped to a minimum of 21.8 degrees on 12 and 13 June in rain, the lowest in the month.

    Clouds thinned out on 14 June and there were sunny periods. The weather remained mainly fine for the next two days.

    An active trough of low pressure over the northern part of the South China Sea affected the territory on 17 June and the weather became overcast with rain. Rain became heavy the next morning, resulting in 8 reports of landslip and 13 reports of flooding. The worst-hit areas were Tseung Kwan O, Sai Kung and Sha Tin where over 100 millimetres of rainfall were recorded. Heavy rain moderated during the day.

    A vortex formed on the trough of low pressure on the evening of 18 June and intensified rapidly into a tropical depression. It then moved northwards to make landfall in the vicinity of Tsuen Wan before entering the inland areas of Guangdong and dissipating on the early morning of 19 June. The Strong Wind Signal No. 3 was hoisted during its passage. The tropical depression brought strong winds and squally showers to Hong Kong.

    Active southwesterlies brought heavy thundery showers to Hong Kong on 20 June. Weather improved in the next two days and there were sunny periods. However, thundery showers returned again on 23 June.

    Under the domination of the subtropical ridge of high pressure over the western Pacific, the weather turned generally fine and hot on 24 June and it continued for the rest of the month.

    Only one tropical cyclone occurred in the South China Sea and the western North Pacific in the month.

    During the month, no aircraft was diverted due to adverse weather.