The Weather of October 1999

    October was warmer and drier than normal. The monthly mean temperature of 26.2 degrees was 1.0 degree higher than normal and ranked the third highest for October. The mean minimum and mean maximum temperatures of 24.6 and 28.6 degrees were the second and sixth highest respectively for October. The total rainfall of 38.8 millimetres in the month was about one quarter of the normal only and the accumulated rainfall of 2 080.5 millimetres since 1 January was about three percent below normal.

    The weather was mainly fine during the first two days of October. Strong northeast monsoon reached the south China coastal areas on the evening of 3 October. Thundery showers associated with the arrival of the monsoon affected Hong Kong and there were strong east to northeasterly winds offshore. Winds moderated on the morning of 4 October and the weather remained mainly cloudy the next day.

    Long sunny periods developed on 6 October and temperatures rose to 31.6 degrees the next afternoon, the highest in the month. On 8 October, the outer rainbands of Typhoon Dan brought some light rain patches to Hong Kong. With Dan moving away, weather became fine and sunny again on 9 October. However, it became hazy. Fine but hazy conditions persisted till 11 October.

    Winds freshened from the east early on 12 October bringing light rain patches and clearing up the haze. Fine and sunny weather returned soon that afternoon and prevailed during the next few days although one or two light rain patches occurred early on 13 October.

    An intense northeast monsoon reached the south China coastal areas on the morning of 16 October. It was accompanied by thunderstorms and heavy showers especially over the eastern parts of Hong Kong. Northerly winds became strong offshore that evening. Under the influence of the dry northeast monsoon, weather turned fine and sunny the next day. It became cloudy and cooler on 18 October with temperatures dropping to 19.9 degrees, the lowest in the month. Fresh to strong northerly winds persisted. During the Chung Yeung holidays on 17 and 18 October, a total of 168 cases of hillfire was reported. The hillfire in Tai Lam Country Park destroyed some 6 000 trees over 160 hectares in the park areas.

    Winds turned to the northeast on 19 October and gradually moderated. Mainly cloudy weather continued the next day. However, long sunny periods developed on 21 October. Mainly fine weather prevailed the next few days apart from some light rain patches during the night of 23 October and on the morning of 24 October.

    It became mainly cloudy again on the afternoon of 29 October. Easterly winds were strong offshore the next morning but moderated on the last day of the month.

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

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