The Weather of April 2004

      April 2004 was slightly drier than usual. The monthly rainfall was 147.2 millimetres, about 9 per cent less than the normal figure of 161.5 millimetres. The accumulated rainfall since the beginning of the year is 354.3 millimetres, about 18 per cent above the normal figure of 299.8 millimetres for the same period.

      A trough of low pressure brought thunderstorms and rain to Hong Kong on the first day of April. It remained cloudy with rain patches on the following two days. On 4 April, the cloud broke and there was some haze. It turned cloudy again that night when an easterly airstream arrived at the coastal area of Guangdong. Mainly cloudy conditions persisted for the next three days, with some rain patches on 7 April.

      A cold front crossed the South China coast on the early morning of 8 April, bringing rain patches and overcast weather to Hong Kong. The cooler weather associated with the cold front lasted for three days. The temperature began to climb steadily to the high twenties as light southerly winds set in between 11 and 13 April.

      A trough of low pressure moved across the coast of South China on 14 April and brought heavy rain and squally thunderstorms to the territory. Rain was heaviest in Hong Kong Island where over 100 millimetres of rainfall was generally recorded. It was overcast with some showers in the ensuing two days.

      Another trough of low pressure approached the south China coast from the north on 17 April, bringing thunderstorms and heavy rain to the territory. As the trough of low pressure moved to the south of Hong Kong, the weather turned fine on 18 April. Generally fine weather continued for the next five days. Under the influence of a warm maritime airstream and with long periods of bright sunshine, it was hot on 22 and 23 April. The maximum temperature on 22 April reached 30.7 degrees, the highest so far this year.

      Local wind strengthened from the east on 24 April. It became cloudy with some light rain patches for two days. As the easterly winds moderated on 26 April, there were sunny periods on that day. Thunderstorms occurred in Hong Kong when a trough of low pressure crossed the south China coast on the morning of 27 April. The weather turned fine during the day as the trough of low pressure moved quickly into the South China Sea. Easterly winds strengthened again on 28 April and brought clouds and rain patches to the territory for two days. The weather became mainly fine with morning mist patches on the last day of the month.

      One tropical cyclone occurred in the western North Pacific in the month. 

      Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.4.  Monthly meteorological figures and departures from normal for April are tabulated in Table 2.