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  • The Weather of December 2016

  • 4 January 2017

    With the northeast monsoon over the south China coastal areas remaining relatively weak for most of the month, December 2016 was warmer than usual. The monthly mean temperature of 19.6 degrees was 1.7 degrees above the normal figure of 17.9 degrees and the third highest for December since record began in 1884. The total rainfall recorded in the month was only 6.6 millimetres, less than one quarter of the normal figure of 26.8 millimetres. But in terms of rainfall for the whole year, the annual total of 3026.8 millimetres was about 26 percent above the yearly normal of 2398.5 millimetres.

    Under the influence of the northeast monsoon, the month started off with fine and dry conditions in Hong Kong on the first two days. The weather became cloudy on 3 December as a band of clouds covered the south China coast and the northern part of the South China Sea. Under light wind conditions, it was hazy with sunny periods over the next couple of days as temperatures climbed to a rather warm 25.9 degrees on 5 December, the highest of the month.

    Apart from a lull in the northeast monsoon with relatively warm weather on 12 and 13 December, further replenishments of continental air brought a spell of generally fine and dry conditions to the territory from 6 to 16 December. Easterly winds freshened over the south China coastal areas on 11 December, but temperatures only began falling significantly as the winds turned northerly on 14 December. It was only then that the weather became appreciably cooler over the next couple of days.

    After a cool and cloudier day on 17 December, the weather soon warmed up again as sunny skies emerged on 18 and 19 December. With moist maritime air edging back towards the coast of Guangdong, increasing cloudiness on 20 December was followed by a day of humid conditions and light rain on 21 December. The rain eased off the next day and the weather turned fine again as dry continental air returned to the south China coastal areas after the passage of a cold front. The strengthening of easterly winds brought patches of light rain on the night of 23 December, and the weather remained mostly cloudy till Christmas Day.

    Despite a fine and relatively warm day on 26 December during another break in the northeast monsoon, the passage of a cold front brought strengthening northerly winds that night and falling temperatures the next day. Windy conditions were enhanced by the presence of a weakening tropical cyclone Nock-Ten over the central part of the South China Sea, with winds reaching gale force on high ground in Hong Kong. Under the influence of the intense northeast monsoon, a continental airstream brought fine and very dry weather to the territory on 27 December, while the first issuance of the Cold Weather Warning this winter saw temperatures plummeting to a minimum of 11.5 degrees the next morning, the lowest in the month.

    After a cloudy day on 28 December, the northeast monsoon started to subside and temperatures gradually recovered with sunny periods towards the end of the month.

  Two tropical cyclones occurred 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 December are tabulated in Table 2.
 

Warnings and Signals issued in December 2016

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
24 / 12 0210 24 / 12 1145
26 / 12 2310 28 / 12 0745


Table 1.2   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 4 / 12 0600 4 / 12 1800
Red 6 / 12 0830 7 / 12 2000
Red 8 / 12 0615 8 / 12 1800
Yellow 11 / 12 0600 11 / 12 1900
Yellow 17 / 12 0600 17 / 12 1945
Yellow 18 / 12 0600 18 / 12 1800
Yellow 25 / 12 0600 25 / 12 1800
Yellow 26 / 12 0600 27 / 12 1145
Red 27 / 12 1145 28 / 12 0045
Red 29 / 12 0600 30 / 12 2315
Yellow 31 / 12 1130 31 / 12 1800


Table 1.3   Cold Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
27 / 12 1620 29 / 12 0930


Table 2   Figures and Departures from Normal - December 2016
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 21.8 degrees C 1.6 degrees above normal
Mean Air Temperature 19.6 degrees C 1.7 degrees above normal
Mean Daily Minimum Air Temperature 17.7 degrees C 1.8 degrees above normal
Mean Dew Point Temperature 13.9 degrees C 2.0 degrees above normal
Mean Relative Humidity 70 % 1 % above normal
Mean Cloud Amount 62 % 10 % above normal
Total Rainfall 6.6 mm 20.2 mm below normal
Number of hours of Reduced VisibilityΔ 89 hours 135.9 hours below normal§
Total Bright Sunshine Duration 168.2 hours 4.0 hours below normal
Mean Daily Global Solar Radiation 12.25 Megajoule / square metre 1.36 Megajoule above normal
Total Evaporation 82.7 mm 1.0 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 2015

daily values of selected meteorological elements for HK for December 2016

The percentile map of mean temperature of December 2016

  Remarks : Extremely high: above 95th percentile
Above normal: between 75th and 95th percentile
Normal: between 25th and 75th percentile
Below normal: between 5th and 25th percentile
Extremely low: below 5th percentile
Percentile and 5-day running average values are
computed based on the data from 1981 to 2010