The Weather of June 1998

    June 1998 was very wet. The total rainfall of 814.5 millimetres, more than double the normal figure of 376.0 millimetres, ranked the fifth highest for the month. The daily rainfall of 411.3 millimetres on 9 June was the highest for June on record. The accumulated rainfall since 1 January amounted to 1 644.7 millimetres which was 66 per cent above normal and the eighth highest for the period. The mean cloud amount of 87 per cent was the eighth highest for June while the total bright sunshine duration of 90.0 hours was the third lowest for the month. It was slightly warmer than usual and the mean minimum temperature of 26.6 degrees was 0.7 degrees above normal, ranking the eighth highest for June.

    The Black Rainstorm Warning Signal was issued for the first time this year on 9 June. This rainstorm warning episode of more than 18 hours was the longest since the warning was introduced in 1992. No tropical cyclone formed over the western North Pacific or the South China Sea in the first half of this year. This has broken the record of late tropical cyclone formation dates in post-war years. The previous record was in 1973 when the first tropical cyclone formed over the South China Sea on 1 July.

    Under the influence of an active southwesterly airstream, the weather on the first two days of the month was cloudy with showers and isolated thunderstorms. A trough of low pressure passed over Hong Kong from the north on the night of 2 June and lingered in the northern part of the South China Sea in the next few days, bringing unsettled weather with scattered showers and isolated thunderstorms to the coastal region. Winds turned from southwesterly to easterly and became strong on the evening of 5 June. Winds gradually moderated the next day. It became cooler and temperatures fell to 21.8 degrees on 7 June, the lowest in the month.

    As this trough of low pressure moved back to the coast from the south, weather deteriorated and turned overcast with frequent heavy showers and squally thunderstorms on 9 June. Over 400 millimetres of rainfall were recorded in most parts of Kowloon and over 500 millimetres in Sai Kung. There were 118 cases of flooding and 45 landslips reported. In northern New Territories, flood water was up to 1.5 metres in some locations. Three families in Sheung Shui and Siu Lam were stranded and rescued by firemen in dinghies. About 50 people were made homeless. About 134 hectares of farmland were inundated with the resulting loss estimated at around 4 million dollars. One man was swept away in a flooded nullah in Quarry Bay and was found dead later. Thundery showers continued the next couple of days.

    As the trough moved away and dissipated on 12 June, weather gradually improved. There were sunny periods during the day with isolated showers till 18 June. Temperatures rose to 32.7 degrees on 16 June, the highest in the month.

    As another trough of low pressure approached from the north, there were occasional thundery showers on 19 and 20 June. Showers eased off the next day but thunderstorms returned on 22 June with unstable southwesterlies and thundery conditions continuing the next two days. Six people were injured by lightning on 23 June.

    There were isolated showers on 25 June, becoming more frequent and thundery the next couple of days as another trough approached from the north again. On 28 June, the trough dissipated and the coastal areas came under the influence of a ridge of high pressure. Apart from a few isolated showers, it was fine with sunny periods till the end of the month. Temperatures rose again to a maximum of 32.7 degrees on 30 June.

    During the month, a total of 8 aircraft was diverted due to adverse weather.