The Weather of March 1999

    March 1999 was very warm with both the mean temperature of 20.4 degrees and the mean minimum temperatures of 18.4 degrees being the sixth highest for the month. During the month of March, the anticyclone over China was relatively weak. In Hong Kong, the mean sea-level pressure was 1011.5 hectopascals, the lowest for the month. A total of 23.6 millimetres of rainfall was recorded in the month and the accumulated rainfall in the first quarter of the year was only 28.1 millimetres against a normal of 138.3 millimetres.

    Under the influence of a dry winter monsoon, it was fine and sunny during the first few days of the month. A humid airstream affected the south China coastal areas on 6 March and visibility deteriorated. Two cargo vessels were reported to have collided off the Kwo Chau Islands in fog, one of them sank. Two crewmen were killed and five were reported missing.

    A cold front crossed the coast of Guangdong early on 8 March. With winds strengthening from the east, the weather became gloomy and misty with periods of rain. The wet conditions prevailed for the next couple of days although winds gradually moderated. Another cold front reached the coastal areas on the evening of 10 March. The fresh to strong northerly winds brought the temperatures down as well as cleared the mist. Winds subsided the next morning.

    It was misty again on 12 March. A 300-tonne cargo vessel sank in poor visibility off the Kwo Chau Islands early that day. Six crewmen were killed and two others reported missing. Visibility remained poor in mist and rain during the next couple of days. The weather improved temporarily on 15 March though it remained mainly cloudy.

    Light rain returned on 16 March although sunny intervals were also reported in the next few days. Under the influence of a maritime airstream, fog affected the coastal areas again on the evening of 20 March. Visibility improved significantly on 21 March, due to the fresh northerly winds brought about by the passage of a cold front the previous evening. On the morning of 22 March, winds became occasionally strong offshore and temperatures dropped to 12.7 degrees, the lowest in the month. Winds moderated during the day.

    Misty and rainy weather returned on 23 March. Fog spread inside the harbour on 25 March, reducing the visibility to 100 metres at Waglan Island that morning. Two cargo vessels collided off the East Lamma Channel that evening. Under the influence of this warm maritime airstream, temperatures rose to 29.5 degrees on 27 March, the highest in the month.

    A cold front crossed the coast of Guangdong late on the evening of 27 March. It was accompanied by rain which was heavy in Sha Tin. Winds strengthened from the east and persisted until 29 March. A dry northerly airstream cleared the clouds on 30 March and it became mainly fine and sunny during the last two days of the month.

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

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