The Weather of April 1998

    April 1998 was the warmest April since records began in 1884. In the absence of significant late-season cold surges and with more southerly winds, temperatures stayed at 20 degrees or above on all but one day. Both the mean temperature of 24.8 degrees and the mean minimum temperature of 22.9 degrees were the highest on record for the month, breaking the previous records of 24.7 and 22.8 degrees set in 1994. Furthermore, the mean maximum temperature of 27.4 degrees was the second highest for April.

    The total rainfall amount of 237.1 millimetres in the month was 75.6 millimetres above the normal figure, and the cumulative rainfall in the first four months of the year reached 495.0 millimetres, which was about 65 per cent more than the normal for the same period. The Amber and Red Rainstorm Warning Signals were issued for the first time this year on 12 and 26 April respectively.

    The month started cloudy with sunny periods in the afternoon. A weak cold front crossed the coast of Guangdong early on 2 April and temperatures dropped to 19.3 degrees, the lowest in the month, on the morning of 3 April. There were light rain patches the next day but the weather turned sunny on 5 April.

    Sunny weather prevailed for the next few days apart from some mist patches and coastal fog on 7 April. It became cloudy on 9 April when winds turned more to the south. Under the influence of a moist southeasterly airstream, there were fog patches in the harbour on the mornings of 10 and 11 April though it was sunny during the days.

    An area of thundery showers associated with a trough of low pressure affected Hong Kong early on 12 April. Over 50 millimetres of rainfall were recorded in Sai Kung and Tung Chung respectively. Mist patches occurred in the next two days and there were isolated thunderstorms early on 14 April.

    A northeasterly airstream cleared the mist in the harbour on the afternoon of 14 April. Under the influence of drier air, the weather turned fine and sunny the next day. Temperatures rose to 30.8 degrees, the highest in the month, on 17 April. Fine weather prevailed until 19 April when it became cloudy. Thunderstorms broke out towards the evening bringing over 20 millimetres of rain to parts of the New Territories. The weather remained mainly cloudy with rain patches during the next couple of days. There were coastal fog patches on the morning of 22 April as winds turned southerly. It was cloudy with isolated showers on 23 April and there were a few isolated thunderstorms the next day.

    A trough of low pressure passed over Hong Kong on 25 April. Isolated heavy showers brought some 60 millimetres of rain to the High Island area . The trough lingered over the northern part of the South China Sea during the next few days. Unsettled weather affected the coastal areas with heavy and squally thundery showers. On the evening of 26 April and early on 27 April, the Peak area recorded over 120 millimetres of rainfall. Over 50 cases of flooding were reported in many parts of Hong Kong and there were landslips in Kennedy Town, Shau Kei Wan and Sau Mau Ping.

    The weather remained mainly cloudy with some light rain patches on 28 and 29 April. Isolated thunderstorms and heavy showers returned on 30 April with over 30 millimetres of rainfall recorded in the northern part of the New Territories.

    No tropical cyclone occurred in the western North Pacific and the South China Sea in the month.

    During the month, only one aircraft was diverted due to adverse weather.