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  • The Weather of January 2017

  • 2 February 2017

    With no significant cold surge affecting the coastal areas of Guangdong, January 2017 became the warmest January in Hong Kong with record-breaking monthly mean temperature of 18.5 degrees and monthly mean minimum temperature of 17.0 degrees, 2.2 degrees and 2.5 degrees above their respective normals. The month was drier than usual in terms of rainfall amount with only 7.8 millimetres in total, less than one-third of the normal of 24.7 millimetres for January.

    Under the influence of an easterly maritime airstream, the weather in Hong Kong was mild with a mixture of sunshine and cloudy episodes for the first five days in the month. The weather turned generally fine on 6 January and with abundant sunshine over the next couple of days, temperatures at the Hong Kong Observatory rose to a maximum of 25.5 degrees on 8 January, the highest of the month. The arrival of a replenishment of the northeast monsoon that night brought cloudier and slightly cooler weather in the next two days.

    With a strengthening easterly airstream and cloud bands associated with a low pressure area over the South China Sea moving in towards the coastal areas of Guangdong, a spell of cloudy and misty weather set in over the territory on 11 January. As replenishments of the northeast monsoon reached the south China coast under an overcast sky, local weather turned progressively cooler with rain patches on 12 - 16 January. With the northeast monsoon moderating gradually and the weather warming up again, the lingering cloud bands started to dissipate and gave way to mainly fine weather on 19 January.

    Following the arrival of a significant replenishment of the northeast monsoon, northerly winds of continental origin brought dry and cooler weather to Hong Kong on 20 - 22 January. Under clear skies, temperatures at the Hong Kong Observatory fell to a minimum of 13.6 degrees on the morning of 22 January, the lowest of the month. With relative humidity falling below 40 percent during the day over a sunny weekend, hill fires were reported in Siu Lek Yuen of Sha Tin. Despite a strengthening easterly airstream on 24 January, fine weather persisted on 23-27 January. Affected by a moist easterly airstream, local weather became cloudy on 28 January with rain patches and poor visibility in some areas over the Chinese New Year holiday period. It also turned appreciably cooler by the end of the month as a fresh to strong easterly airstream brought a replenishment of the northeast monsoon to the south China coastal areas on the night of 30 January.

  One tropical cyclone 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 January are tabulated in Table 2.
 

Warnings and Signals issued in January 2017

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
24 / 1 0200 24 / 1 0745
24 / 1 2325 25 / 1 0615
30 / 1 2200 31 / 1 0845


Table 1.2   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 1 / 1 0600 1 / 1 1800
Yellow 2 / 1 0600 2 / 1 1800
Yellow 8 / 1 0600 8 / 1 1800
Red 21 / 1 0600 22 / 1 2130
Red 27 / 1 1145 27 / 1 1945
Yellow 28 / 1 0745 28 / 1 1300


Table 1.3   Cold Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
21 / 1 1620 22 / 1 0945


Table 2   Figures and Departures from Normal - January 2017
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 20.6 degrees C 2.0 degrees above normal
Mean Air Temperature 18.5 degrees C 2.2 degrees above normal
Mean Daily Minimum Air Temperature 17.0 degrees C 2.5 degrees above normal
Mean Dew Point Temperature 14.7 degrees C 3.3 degrees above normal
Mean Relative Humidity 79 % 5 % above normal
Mean Cloud Amount 66 % 5 % above normal
Total Rainfall 7.8 mm 16.9 mm below normal
Number of hours of Reduced VisibilityΔ 81 hours 158.8 hours below normal§
Total Bright Sunshine Duration 145.1 hours 2.1 hours above normal
Mean Daily Global Solar Radiation 11.10 Megajoule / square metre 0.93 Megajoule above normal
Total Evaporation 59.4 mm 11.9 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 2016

daily values of selected meteorological elements for HK for January 2017

The percentile map of mean temperature of January 2017

  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


Extract of Meteorological Observations in Hong Kong for January 2017