The Weather of July 1997

    After a very wet June, July 1997 continued with exceptional rainfall from active troughs of low pressure affecting the south China coast. The cumulative rainfall of 1 529.6 millimetres in June and July was the highest for these two consecutive months. The month's total rainfall of 746.0 millimetres was more than double the normal figure of 323.5 millimetres, ranking the fourth highest for the month of July. Furthermore, the month's total bright sunshine duration of 125.1 hours was the lowest on record. The first Tropical Cyclone Warning Signal of this year was hoisted on the last day of the month.

    A Rainstorm Black Warning was issued on 1 July and Rainstorm Red Warnings were also issued on the first three days of the month while Landslip Warnings and Flood Warnings were issued on two and eight occasions respectively. The accumulated rainfall since 1 January of 2 154.7 millimetres was 64 per cent above normal.

    A trough of low pressure lingered along the coastal areas of Guangdong and brought unsettled weather to Hong Kong at the beginning of the month. Rain was particularly heavy with thunderstorms on the morning of 1 July in urban areas. A total of 34 cases of flooding and two minor landslips were reported.

    Sixty-five cases of flooding and more than 55 cases of landslips occurred on 2 July as heavy rain and thundery showers continued. The most severe landslips occurred in Sha Tin and Tsuen Wan. In Sha Tin where the heaviest downpour took place, a landslip at Ten Thousand Buddha Monastery killed one person, destroyed three temples and damaged several village huts. Dozens of villagers and missionaries had to be evacuated. At Sham Tseng, eight people were injured when an embankment collapsed while they were clearing an earlier landslip near Lido Beach.

    In the northern part of the New Territories, firemen had to use dinghies to rescue villagers whose houses were surrounded in flood early on 3 July. About 190 hectares of farmland were inundated, agricultural loss was estimated at six million dollars. Heavy rain brought the temperatures down to 22.6 degrees that evening, the lowest in the month.

    During the heavy rain in the early hours on 4 July, a scaffolding in Sheung Wan collapsed injuring one person. Rain intensity weakened and became infrequent during the day but the weather remained generally cloudy with isolated thunderstorms and heavy showers for the next few days. Over 140 cases of landslip were reported during the first four days in July.

    The trough dissipated on 7 July and there were only isolated showers the next couple of days. As another trough over southern China moved southwards, thundery and heavy showers returned on 10 July. Two people were injured when a 15-metre banyan tree crashed on to three cars in Causeway Bay.

    The Pacific ridge extended westwards and rain became infrequent on 11 July. There were long sunny periods on 12 and 13 July.

    As a trough of low pressure was forming over the northern part of the South China Sea, rain and isolated thunderstorms returned to affect Hong Kong again starting 14 July. Showers became heavy the next day and prevailed for the next few days. Sixteen cases of flooding were reported, especially in Mong Kok and Tsuen Wan on the evening of 15 July. Due to the excessive rainfall collected in the reservoirs, the overflow systems of 14 reservoirs had to be activated on 17 July. A 20-metre tree collapsed in Kowloon Tong damaging a private car on 18 July. Five persons were injured in North Point when a concrete balcony collapsed on 19 July after days of rainfall. Rainfall was particularly heavy in Sha Tau Kok where flood water was reported to be two and a half metres deep. Flooding also occurred in Tsing Yi and farmlands in Yuen Long were inundated. There were landslips at Nam Long Shan Road in Aberdeen and in Tsing Lung Tau.

    The trough eventually dissipated on 20 July. Weather became fine and sunny on 21 July and fine conditions prevailed for the next couple of days. Cloud amount increased on 24 July and there were isolated heavy and thundery showers the next day.

    Fine and sunny weather returned on 26 July. Temperatures increased progressively the next few days, reaching a maximum of 33.2 degrees on 30 July, the highest in the month.

    An area of low pressure over the northern part of the South China Sea developed into a tropical depression on the last day of the month and the Stand By Signal, No. 1 , was hoisted in the afternoon. Outer rainbands began to affect Hong Kong in the evening.

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

    During the month, a total of 11 aircraft was diverted due to adverse weather.