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The Weather of December 2005

     December 2005 was drier than normal with only 9.5 millimetres of rainfall. Despite a dry December, the year 2005 finished as the 3rd wettest year since record began in 1884. The annual rainfall was 3214.5 millimetres, some 45 percent above the normal figure of 2214.3 millimetres.

     It was fine but hazy in the first three days of December 2005. As a cold front moved across the south China coast in the early morning of 4 December, the visibility improved, and the weather turned cloudy, cold and dry in the ensuing three days. The first Cold Weather Warning of the winter was issued on 5 December.

     With the moderation of the northeast monsoon, there were sunny periods on 8 December and the weather was mild in the next three days. A surge of the winter monsoon reached Hong Kong again on the early morning of 12 December, bringing cool weather to the territory. The temperature and relative humidity dropped further on 15 December when the winter monsoon strengthened. It was cold and very dry in the next four days. The weather warmed up briefly on 20 December, but turned cold and windy again on 21 December when an intense surge of the winter monsoon arrived at southern China. Three people in Sham Tseng were hurt as they fell in strong winds that morning. The weather stayed cold and very dry on 22 and 23 December. The minimum temperature dropped to 10.4 degrees on 22 December, the lowest so far this winter. Frost was reported in the Sha Tin Racecourse on the morning of 23 December.

     The temperature rose gradually on 24 December as the winter monsoon weakened. It was mainly fine in the next three days. A cloud band associated with an area of low pressure over the South China Sea brought cloudy weather and some rain to the territory between 28 and 30 December. It was mainly fine on the last day of the year.

     Only one tropical cyclone occurred in the western North Pacific and the 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 1.3.  Monthly meteorological figures and departures from normal for December are tabulated in Table 2.


 

Warnings and Signals issued in December 2005


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
4 / 12 0245 4 / 12 1245
15 / 12 0245 15 / 12 0745
21 / 12 0615 22 / 12 1045


Table 1.2   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 4 / 12 0600 5 / 12 0600
Red 5 / 12 1130 8 / 12 0600
Red 8 / 12 1130 8 / 12 1800
Yellow 11 / 12 0600 12 / 12 0600
Red 12 / 12 0600 12 / 12 1800
Red 13 / 12 0600 13 / 12 1800
Red 14 / 12 0600 19 / 12 1800
Red 21 / 12 0000 23 / 12 1800
Yellow 23 / 12 1800 25 / 12 1115
Red 25 / 12 1115 26 / 12 0600
Yellow 26 / 12 0600 27 / 12 1800


Table 1.3   Cold Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
5 / 12 1600 7 / 12 1145
14 / 12 1600 16 / 12 1130
17 / 12 1630 19 / 12 1130
21 / 12 1600 23 / 12 1130


Table 2   Figures and Departures from Normal - December 2005

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 19.1 degrees C 1.4 degrees below normal
Mean Air Temperature 17.0 degrees C 0.6 degree below normal
Mean Daily Minimum Air Temperature 15.0 degrees C 0.4 degree below normal
Mean Dew Point Temperature 9.7 degrees C 1.5 degrees below normal
Mean Relative Humidity 64 % 4 % below normal
Mean Cloud Amount 59 % 10 % above normal
Total Rainfall 9.5 mm 17.8 mm below normal
Number of hours of Reduced VisibilityΔ 276 hours 58.4 hours above normal§
Total Bright Sunshine Duration 179.7 hours 1.8 hours below normal
Mean Daily Global Solar Radiation 11.41 Megajoule / square metre 0.62 Megajoule below 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 and visibility which was observed at the Hong Kong International Airport.
  Δ

The visibility readings at the Hong Kong International Airport are based on hourly observations by professional meteorological observers in 2004 and before, and average readings over the 10-minute period before the clock hour of the visibility meter near the middle of the south runway from 2005 onwards. The change of the data source in 2005 is an improvement of the visibility assessment using instrumented observations following the international trend.

Before 10 October 2007, the number of hours of reduced visibility at the Hong Kong International Airport in 2005 and thereafter displayed in this web page was based on hourly visibility observations by professional meteorological observers. Since 10 October 2007, the data have been revised using the average visibility readings over the 10-minute period before the clock hour, as recorded by the visibility meter near the middle of the south runway.


  *   Departure from 1961-1990 climatological normal, except for number of hours of reduced visibility.
  §   Departure from mean value between 1997 and 2004.


daily values of selected meteorological elements for HK for December 2005

Extract of Meteorological Observations in Hong Kong for December 2005