The Weather of December 2003

   December 2003 was dry with an abundance of sunshine. The mean cloud amount of just 24 per cent in the month was the third lowest on record, resulting in a total of 249.1 hours of bright sunshine, some 37 per cent more than the normal figure. Only a trace of rainfall was recorded during the month, against a normal figure of 27.3 millimetres. This was the second lowest for December on record, along with seven other years. The accumulated annual rainfall is 1 941.9 millimetres, about 12 per cent below the normal figure of 2 214.3 millimetres.

   Under the influence of a broad ridge of high pressure, the weather was fine and dry in the first six days of December 2003. With lighter winds and long periods of sunshine, the temperature on 6 December rose to 25.3 degrees, the highest of the month. A weak cold front crossed the coast of South China in the small hours of 7 December. The weather became cloudy with haze. There were also light rain patches that evening and during the early hours of the next day. Clouds dispersed in the afternoon of 9 December.

   It was fine and dry for the rest of the month apart from some cloudy periods on 20 December. Haze was reported on 10 and 17 December in the lulls of the northeast monsoon.

   On 18 December, pressure in Central China built up rapidly and an intense surge of cold air arrived at the South China coast that evening. Winds strengthened from the north overnight and the mean wind speed recorded at Waglan Island exceeded 50 kilometres per hour. Temperature fell to a minimum of 10.3 degrees in the early morning of 20 December, the lowest recorded so far this winter. The Cold Weather Warning was issued for the first time this winter.

   It remained cold on 21 December but the temperature rose gradually in the next few days as the northeast monsoon moderated. Haze was reported again on 22 and 24 December. A replenishment of cool air arrived on 27 December and the morning temperature dropped to 13 degrees. It remained fine and dry for the next three days. Haze occurred again on the last day of the year under light wind conditions.

   A total of 2 tropical cyclones 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 1.3. Monthly meteorological figures and departures from normal for December are tabulated in Table 2.