The Weather of October 1998

    October 1998 was much warmer than normal, with the mean temperature of 26.1 degrees and the mean minimum temperature of 24.3 degrees being the third and second highest respectively on record for October. Furthermore, the mean temperature from January to October this year reached 24.5 degrees, the highest on record for the same period. On the other hand, the relative humidity of 21 per cent recorded early on 17 October equalled the lowest record for the month previously made in 1991. Two tropical cyclones necessitated the hoisting of Tropical Cyclone Warning Signals in the month and the mean pressure of 1 011.6 hectopascals was the eighth lowest for October. The total rainfall of 133.9 millimetres in the month was 10.9 millimetres below the normal figure. However the cumulative rainfall since 1 January, 2 522.1 millimetres, was still 17 per cent more than the normal for the same period.

    Under the influence of a continental airstream, the fine and dry weather at the end of September continued into October. A total of 25 hill fires broke out on 3 October. As a result, three huts in Yuen Long were destroyed and eight people became homeless. With a tropical depression forming over the South China Sea on 3 October and moving towards Hainan, the weather became cloudy. Rainbands associated with this tropical depression began to affect Hong Kong towards midnight, with easterly winds strengthening offshore. Winds moderated on 5 October but some heavy showers occurred in the urban areas and the northern part of the New Territories the next afternoon.

    Rain eased off on 7 October and it became mainly fine apart from some mist in the morning. Sunny periods continued for another day. Cloudy weather returned on 9 October and there were some isolated heavy showers which became more widespread the next day.

    Rain eased off on 11 October and the weather improved the next day with long sunny periods. Dry and sunny weather prevailed during the next week. Meanwhile, it was hazy on 14 October and temperatures rose to 32.3 degrees, the highest in the month, that afternoon. Typhoon Zeb came within 800 kilometres of Hong Kong on 15 October but did not bring any significant weather to Hong Kong. However the coupled effect of Zeb and the winter monsoon gave rise to occasional strong northerly winds offshore.

    Winds subsided on 16 October but fine and dry conditions persisted for the following week apart from some light rain patches between 20 and 22 October. Twenty-four hill fires were reported on 18 October.

    Another typhoon, Babs, approached from the southeast on 23 October. Winds became strong the next day and rainbands associated with Babs affected Hong Kong on 25 and 26 October. There were some storm-related accidents and a few people were injured. Temperatures dropped to 21.7 degrees, the lowest in the month, on 26 October.

    The weather improved on 27 October with Babs moving away. Fine and sunny weather prevailed till the end of the month.

    Three 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.