The Weather of August 1997

    August 1997 was the third consecutive month with higher than normal rainfall. At 829.0 millimetres, rainfall amount for August was the fourth highest for that month. The accumulated rainfall for June, July and August was 2 358.6 millimetres and the highest for these three months. Also, the accumulated rainfall since 1 January was 2 983.7 millimetres and the highest ever recorded for the period.

    The monthly mean amount of cloud of 77 per cent was the eighth highest on record and the total bright sunshine duration of 141.3 hours the seventh lowest. Two tropical cyclones, Victor and Zita, necessitated the hoisting of Tropical Cyclone Warning Signals. The Increasing Gale or Storm Signal No. 9 was hoisted on 2 August, the first time since 1983.

    The weather was cloudy with outbreaks of rain on the first day of the month as the rainbands of Victor continued to affect Hong Kong. As the centre of Victor crossed the western part of the New Territories on the evening of 2 August, parts of Hong Kong were affected by cyclonic winds of gale or storm force. There were also torrential rain and thunderstorms over the whole territory. Winds subsided early on 3 August as Victor moved away and rain eased off the next day. It became sunny apart from some isolated showers during the next two days.

    Under the influence of an unstable southwesterly airstream, the weather in the next week or so was generally cloudy with occasional heavy or thundery showers. The lowest temperature in the month, 23.8 degrees, was recorded on 8 August. Over 60 millimetres of rainfall were recorded in Cheung Sha Wan in two hours on 9 August, and a group of 11 students and teachers were stranded over a small hill in Ma On Shan where a creek flooded its banks. On 12 August, over 300 millimetres of rainfall were recorded in Tai Po, resulting in severe flooding and affecting over 1 000 homes. Flood water was more than one metre deep in Ting Kok. A small fire broke out on a ship as it was struck by lightning near Tsing Yi on the early morning of 13 August.

    It turned sunny during the day on 14 August. Fine weather prevailed during the next couple of days apart from a few thunderstorms on 16 August. On that day, lightning struck two aircraft and five technicians working outdoors at the airport were slightly injured. It became fine but hazy on 17 August and these conditions persisted for the next few days. Temperatures rose to 33.2 degrees, the highest in the month, on 18 August.

    Due to the formation of Tropical Depression Zita over the northern part of the South China Sea, the weather turned cloudy on 20 August with thundery showers in the afternoon. The rainbands of Zita affected Hong Kong most severely on 22 August when the Rainstorm Black Warning had to be issued. There were at least 80 reports of flooding and 10 reports of landslips over Hong Kong.

    The weather remained cloudy with heavy showers at times until early 27 August when it became fine again. Sunny weather prevailed till the end of the month.

    Nine tropical cyclones occurred in the western North Pacific and the South China Sea in the month.

    During the month, a total of 85 aircraft was diverted due to adverse weather.