The Weather of April 2006

    April 2006 was warmer and wetter than usual. The mean temperature of 23.9 degrees was 1.7 degrees above the normal, the tenth highest for April. The monthly rainfall of 199.2 millimetres was about 23 percent above the normal figure of 161.5 millimetres. The accumulated rainfall since the beginning of this year was 301.6 millimetres, about the same as the normal figure of 299.8 millimetres.

    It was fine and warm on the first day of April. Affected by a maritime airstream, there were fog patches in the morning in the next three days. The weather was mainly fine on April 5 and 6. A cold front moved across the south China coast on the afternoon of April 6. The weather became overcast and slightly cooler on April 7.

    Sunny periods returned on April 8 when a ridge of high pressure dominating over southeastern China. Mist occurred on the morning of April 9.

    Under the influence of the southwest monsoon, it was hot with a few showers from April 10 to 12. After the passage of another cold front across the coast of Guangdong on the morning of April 13, the weather became rainy and appreciably cooler that night. It remained cool with some rain patches in the next three days. The temperature fell to 15.1 degrees on April 15, the lowest in the month.

    The weather improved on April 17 and remained generally fine in the next two days. Fresh easterly winds brought cloudy and misty conditions to the territory later on Apri 20l. The clouds dispersed and there were sunny periods on April 21. Under the influence of a maritime airstream, it was mainly fine and hot on April 22 and 23. The temperature rose to 30.1 degrees on April 23, the highest in the month.

    Heavy rain and thunderstorm began to buffet the territory in the small hours of April 24 when a trough of low pressure reached the south China coast. The Black Rainstorm Warning was issued for the first time this year. During the heavy downpour, over 200 millimetres of rainfall was recorded in the western part of Hong Kong Island. There were 16 reports of flooding, mainly in Hong Kong Island. It was mainly cloudy with some showers in the next three days.

    A trough of low pressure over the south China coast brought heavy rain and thunderstorms to Hong Kong again on April 28. More than 100 millimetres of rainfall was recorded in Tsuen Wan, Sha Tin and Sai Kung. As the trough of low pressure weakened, the weather improved gradually on April 29. There were sunny periods on the last day of the month.

    There was no tropical cyclone over the South China Sea and 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 1.5.  Monthly meteorological figures and departures from normal for March are tabulated in Table 2.