The Weather of January 2012

    Under the dominance of the winter monsoon, January 2012 was colder than usual. The mean temperature of the month was 15.1 degrees, 1.2 degrees below the normal figure of 16.3 degrees. The month was also wetter and gloomier than usual. The monthly rainfall of 42.1 millimetres was 17.4 millimetres above normal. The monthly total duration of bright sunshine was 86.0 hours, a deficit of 40 percent against to the normal figure of 143.0 hours.

    Under the influence of a continental airstream, the weather in Hong Kong was mainly fine and dry for the first three days of the month. An intense surge of the winter monsoon reached the coastal areas of Guangdong during the night on 3 January and brought cold weather with rain patches to the territory from 4 to 6 January. The weather remained cloudy and cool on 7 January. With clouds thinning out, it became generally fine with some haze for the ensuing three days.

    Affected by a broad rain bearing cloud band over southern China, local weather turned rainy from 11 to 13 January. While the winter monsoon moderated in the next two days, the rain continued with mist and fog patches. The visibility at Waglan Island once fell to 100 metres on the morning of 15 January. Meanwhile, a cold front formed over inland Guangdong on 15 January and moved across the coastal areas the next morning bringing cooler weather to Hong Kong on 16 January.

    With the prevalence of a relatively mild easterly airstream, there was plenty of sunshine and the temperature rose gradually from 17 to 19 January. The temperature at the Observatory reached a maximum of 22.4 degrees on 19 January, the highest of the month. Local weather became cloudy with some coastal fog when the easterly airstream freshened for the next two days.

    An intense winter monsoon reached the south China coast on the morning of 22 January and the weather became progressively colder with rain patches from 22 to 26 January. The temperature at the Observatory fell to a minimum of 7.4 degrees on the morning of 25 January, the lowest during the Lunar New Year holidays since 1996. With the winter monsoon over the south China coastal areas being generally replaced by a humid easterly airstream, local weather was misty with temperatures rising gradually on 27 and 28 January. Affected by a weak replenishment of the winter monsoon, the weather became slightly cooler for the next two days. A dry continental airstream brought mainly fine and dry weather to the territory on the last day of the month.

There was no tropical cyclone over the South China Sea and 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 January are tabulated in Table 2.

Warnings and Signals issued in January 2012

**Table 1.1 Strong Monsoon Signal**
Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
25 / 1	0445	25 / 1	0745

**Table 1.2 Fire Danger Warnings**
Colour	Beginning Time		Ending Time
Colour	Day/Month	HKT	Day/Month	HKT
Yellow	1 / 1	0600	2 / 1	1800
Yellow	8 / 1	0600	8 / 1	2200
Red	31 / 1	0600	31 / 1	1930

**Table 1.3 Cold Weather Warning**
Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
3 / 1	1620	7 / 1	1100
21 / 1	1620	27 / 1	1200
30 / 1	1620	31 / 1	0845

**Table 2 Figures and Departures from Normal - January 2012**
Meteorological Element	Figure of the Month	Departure from Normal*
Mean Daily Maximum Air Temperature	17.0 degrees C	1.6 degrees below normal
Mean Air Temperature	15.1 degrees C	1.2 degrees below normal
Mean Daily Minimum Air Temperature	13.5 degrees C	1.0 degree below normal
Mean Dew Point Temperature	11.9 degrees C	0.5 degree above normal
Mean Relative Humidity	82 %	8 % above normal
Mean Cloud Amount	79 %	18 % above normal
Total Rainfall	42.1 mm	17.4 mm above normal
Number of hours of Reduced VisibilityΔ	223 hours	25.1 hours below normal§
Total Bright Sunshine Duration	86.0 hours	57.0 hours below normal
Mean Daily Global Solar Radiation	8.16 Megajoule / square metre	2.01 Megajoule below normal
Total Evaporation	54.8 mm	16.5 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 1981 - 2010 climatological normal, except for number of hours of reduced visibility
§ Departure from mean value between 1997 and 2011

daily values of selected meteorological elements for HK for January 2012

Rainfall Map For January 2012 (isohyets are in millimetres)

Extract of Meteorological Observations in Hong Kong for January 2012