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The Weather of December 2004

    December 2004 was warmer than normal despite a cold snap in the last few days of the month. The mean temperature of 19.1 degrees was the sixth highest for December. December 2004 was also drier than normal. Against the normal figure of 27.3 millimetres, only a trace of rainfall was recorded in the month. This was the second lowest for December on record, along with eight other years. The annual rainfall of 1738.6 millimetres in 2004 was about 21 percent below the normal figure of 2214.3 millimetres.

    The first two days of December 2004 was sunny and warm. It became cloudy on 3 December. Clouds dispersed the next day as a dry northeast monsoon arrived at the south China coast. The dry continental air maintained generally fine weather in Hong Kong until 20 December. Under dry conditions, a hill fire occurred in Pat Sin Leng on 5 and 6 December and destroyed about 11,000 trees.

    A fresh to strong easterly airstream prevailed over southeastern China on 21 and 22 December, bringing cloudy weather to the territory. With the passage of a cold front through Hong Kong on the night of 22 December, local weather turned fine on 23 December. Mainly fine conditions continued on the following three days. However, it was hazy on 25 December with visibility at the Hong Kong International Airport dropping to 4300 metres in the afternoon.

    While it was sunny and mild during the day on 27 December, the temperature started to fall that evening when an intense surge of winter monsoon reached the coast of Guangdong. It was cold throughout the rest of the month. Temperatures fell to 8.2 degrees in the urban area on the morning of 31 December, the lowest in the month.

    A total of three tropical cyclones occurred in the western North Pacific and South China Sea 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 December are tabulated in Table 2.


 

Warnings and Signals issued in December 2004


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
4 / 12 0520 5 / 12 1145
28 / 12 1210 29 / 12 0350
30 / 12 1800 1 / 1 0845


Table 1.2   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Red 4 / 12 0600 6 / 12 0600
Red 7 / 12 0000 9 / 12 0600
Red 10 / 12 0600 10 / 12 1800
Yellow 11 / 12 0600 12 / 12 0655
Red 12 / 12 0655 13 / 12 2315
Yellow 19 / 12 0600 20 / 12 0600
Yellow 25 / 12 0600 28 / 12 0600
Yellow 30 / 12 1800 31 / 12 1300
Red 31 / 12 1300 3 / 1 0600


Table 1.3   Frost Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
31 / 12 1630 1 / 1 0945


Table 1.4   Cold Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
28 / 12 1315 2 / 1 1630


Table 2   Figures and Departures from Normal - December 2004

Meteorological Element Figure of the Month Departure from Normal
Mean Daily Maximum Air Temperature 21.1 degrees C 0.6 degree above normal
Mean Air Temperature 19.1 degrees C 1.5 degrees above normal
Mean Daily Minimum Air Temperature 17.2 degrees C 1.8 degrees above normal
Mean Dew Point Temperature 13.1 degrees C 1.9 degrees above normal
Mean Relative Humidity 70 % 2 % above normal
Mean Cloud Amount 40 % 9 % below normal
Total Rainfall Trace 27.3 mm below normal
Total Bright Sunshine Duration 216.6 hours 35.1 hours above normal
Mean Daily Global Solar Radiation 12.32 Megajoule / square metre 0.29 Megajoule above normal
Total Evaporation 99.4 mm 12.1 mm below normal


Remarks :   All measurements were made at the Hong Kong Observatory except sunshine, solar radiation and evaporation which were recorded at King's Park Meteorological Station.


daily values of selected meteorological elements for HK for December 2004

Extract of Meteorological Observations in Hong Kong for December 2004