The Weather of December 2006

December 2006 was sunnier and warmer than normal. The monthly total bright sunshine duration of 209.7 hours was 28.2 hours above normal. With an abundance of sunshine, the monthly mean temperature of 18.2 degrees was 0.6 degree higher than normal. Under dry conditions, the Red Fire Danger Warning was issued for consecutive 232.5 hours from 16 to 26 December.

The monthly rainfall was 29.9 millimetres, 2.6 millimetres above the normal. The annual rainfall for 2006 was 2627.8 millimetres, about 19 per cent higher than the normal figure of 2214.3 millimetres.

Under the influence of the northeast monsoon, the weather was generally fine in the first seven days of the month. With the moderation of the northeast monsoon, it was warm and hazy on 8 December with the maximum temperature rising to 25.6 degrees, the highest in the month.

The weather turned cloudy on 9 December when a cold front moved across the south China coast that morning. The weather stayed cloudy the next day. It was hazy with sunny periods during the day on 11 and 12 December.

A surge of northeast monsoon reached the south China coastal area on 13 December, bringing some rain to the territory. It was cool and rainy in the next two days. A replenishment of the northeast monsoon cleared the clouds later on 16 December. The weather became fine, cold and dry in the ensuing two days. The temperature on 18 December dropped to 12.0 degrees, the lowest so far in the month. Under the influence of a continental flow, generally fine and dry weather persisted for the rest of the month.

Three tropical cyclones 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 2006

Table 1.1 Strong Monsoon Signal

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
16 / 12	0945	17 / 12	0745

Table 1.2 Fire Danger Warnings

Colour	Beginning Time		Ending Time
Colour	Day/Month	HKT	Day/Month	HKT
Yellow	2 / 12	0600	4 / 12	0600
Yellow	10 / 12	0600	11 / 12	0600
Red	16 / 12	1200	26 / 12	0430
Yellow	26 / 12	0430	28 / 12	1130
Red	28 / 12	1130	29 / 12	0600
Yellow	29 / 12	0600	29 / 12	1800
Yellow	30 / 12	0645	1 / 1	1800

Table 1.3 Cold Weather Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
16 / 12	1620	18 / 12	1045

Table 2 Figures and Departures from Normal - December 2006

Meteorological Element	Figure of the Month	Departure from Normal*
Mean Daily Maximum Air Temperature	20.4 degrees C	0.1 degree below normal
Mean Air Temperature	18.2 degrees C	0.6 degree above normal
Mean Daily Minimum Air Temperature	16.1 degrees C	0.7 degree above normal
Mean Dew Point Temperature	12.4 degrees C	1.2 degrees above normal
Mean Relative Humidity	70 %	2 % above normal
Mean Cloud Amount	47 %	2 % below normal
Total Rainfall	29.9 mm	2.6 mm above normal
Number of hours of Reduced VisibilityΔ	287 hours	62.9 hours above normal§
Total Bright Sunshine Duration	209.7 hours	28.2 hours above normal
Mean Daily Global Solar Radiation	12.71 Megajoule / square metre	0.68 Megajoule above normal
Total Evaporation	83.4 mm	28.1 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.
	The calibration factors of the pyranometer at King's Park in 2006 and 2007 have been re-computed based on the results of a regional instrument comparison in Asia in 2007. The readings of total global solar radiation at King's Park in 2006 and 2007 displayed in this web page before 13 June 2008 have been revised on 13 June 2008 using the new calibration factors.
* Departure from 1961-1990 climatological normal, except for number of hours of reduced visibility.
§ Departure from mean value between 1997 and 2005.

daily values of selected meteorological elements for HK for December 2006

Extract of Meteorological Observations in Hong Kong for December 2006