The Weather of October 1997

    October 1997 was warmer than normal and the mean temperature of 25.9 degrees was the seventh highest for the month. The mean minimum temperature of 24.3 degrees also ranked the second highest for October. With a ridge of high pressure dominating most of the time over China, the mean pressure of 1 016.0 hectopascals was the fifth highest for October.

    Although the total rainfall in the month was only 112.8 millimetres or 32.0 millimetres below the normal figure, the accumulated rainfall since 1 January of 3 329.4 millimetres was 55 per cent above the normal figure and was the highest ever recorded for the period. In fact, this figure has surpassed the record of maximum annual rainfall of 3 247.5 millimetres set in 1982.

    The weather was cloudy with some isolated showers during the first couple of days of October. It turned fine and sunny on 4 October but clouds returned the next afternoon and isolated heavy showers occurred in the eastern areas early on 6 October.

    From 7 October through 10 October, the weather was mainly fine apart from some isolated showers on 8 October.

    Cloud amount increased on 11 October and there were some isolated heavy showers around midday on 12 October. The weather improved rapidly and there were long sunny periods in the afternoon. Fine weather prevailed for the next couple of days.

    On the afternoon of 16 October, although it was sunny in the urban areas, isolated heavy showers affected the northwestern part of the New Territories where over 30 millimetres of rainfall were recorded. It became cloudy the next day. Thundery showers affected the eastern part of Hong Kong that evening, parts of Hong Kong Island recorded over 100 millimetres of rainfall.

    The weather turned sunny on 19 October, it was also misty or hazy during the next few days. Temperatures rose to 30.4 degrees, the highest in the month, on 21 October. While it remained mainly fine, some isolated showers occurred on 23 October and the mist was cleared the next day.

    Then the winter monsoon strengthened over China. A cold front crossed the south China coast on the evening of 26 October. Temperatures dropped to 19.5 degrees, the lowest in the month, on 28 October. Under the influence of the winter monsoon, fine, sunny and dry weather prevailed till the end of the month.

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

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