The Weather of January 1999

    January 1999 was warmer than normal. The mean temperature of 17.3 degrees and the mean minimum temperature of 15.5 degrees were the eighth and the seventh highest respectively on record for the month. The total rainfall in the month was 4.5 millimetres, about one fifth of the normal amount.

    The year started cloudy with some light rain patches as winds freshened from the east. Winds subsided during the day and it became fine and sunny soon. Under the influence of a dry continental airstream, sunny and dry conditions prevailed until 9 January when cloudy weather returned. The weather remained cloudy with sunny intervals during the next couple of days.

    An intense surge of the winter monsoon brought cold and rainy weather to southern China on 12 January with temperatures dropping to 10.3 degrees, the lowest in the month. It remained generally cold with rain patches during the next few days. Temperatures in the northern part of the New Territories dropped to about 7 degrees on 13 January. A further replenishment of the winter monsoon reached the south China coastal areas on the afternoon of 14 January, with winds strengthening from the north and bringing drier air to our region. Winds moderated early on 16 January.

    There were some light rain patches again on 17 and 18 January. Haze affected local areas on 18 January. Visibility was reduced to 1800 metres in the harbour and 1400 metres at Chek Lap Kok the next day. Visibility improved significantly in the harbour on 20 January, but low values of visibility down to 1100 metres were still experienced at the airport. There were light rain patches the following couple of days.

    Fog occurred in Chek Lap Kok on the morning of 23 January reducing visibility to 600 metres. Mist and haze lingered around the western part of Hong Kong in the next two days although it was fine and sunny elsewhere.

    Winds freshened from the east on 26 January and fine weather was generally experienced in Hong Kong. Temperatures climbed up to 25.0 degrees, the highest in the month, on 28 January.

    A fresh northeast monsoon brought cloudy conditions and cooler air to local areas on 29 January. As winds subsided, sunny periods developed during the last two days of the month.

    There was no tropical cyclone over the western North Pacific and the South China Sea in the month of January.

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