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  • The Weather of November 2017

  • 4 December 2017

    The weather in Hong Kong was gloomier and more humid than usual in November 2017. The duration of bright sunshine in the month was only 114.3 hours, about 37 percent below the normal figure of 180.1 hours and the third lowest for November on record. The monthly mean temperature was 22.2 degrees, 0.4 degree above the normal figure of 21.8 degrees. Despite the rather cloudy and more humid conditions for most part of the month, the monthly rainfall was only 31.2 millimetres, about 17 percent below the normal of 37.6 millimetres. The accumulated rainfall this year up to November was 2572.1 millimetres, a surplus of about 8 percent above the normal of 2371.7 millimetres for the same period.

    Under the influence of a dry northeast monsoon, the weather in Hong Kong was generally fine and dry for the first three days of the month. A freshening of the northeast monsoon brought cloudy weather with some light rain patches on 4 November, before fine weather returned the next day.

    While the northeast monsoon prevailed on 6 – 8 November, moister air moved in towards the coastal areas of Guangdong and brought clouds and rain patches to Hong Kong. Despite the strengthening of an easterly airstream and some light rain on the night of 8 November, winds soon subsided the next day and clouds gradually dissipated. A fine day on 10 November saw temperature at the Hong Kong Observatory rising to a maximum of 28.4 degrees, the highest of the month.

    A replenishment of the northeast monsoon reached the south China coast and the weather in Hong Kong turned cloudy again on 11 November. As a tropical cyclone Haikui made its way across the northern part of the South China Sea, the combined effect between the northeast monsoon and a weakening Haikui resulted in windy and rainy weather in Hong Kong over the next couple of days. Generally cloudy conditions then persisted for another two days before fine weather returned on 16 – 17 November.

    Meanwhile, a cold front formed over southern China and crossed the coast of Guangdong on 18 November. Local weather became cloudy with rain patches persisting till the next day. As cool air under a northerly airstream continued to spread southwards, the weather in Hong Kong got progressively cooler. Even though the weather turned fine on 22 November, temperature continued to fall and a minimum of 15.5 degrees, the lowest of the month, was recorded at the Hong Kong Observatory the next morning.

    The northerly winds lasted till 26 November and winds then turned increasingly to an easterly direction under a mixture of clouds and sunshine. Local temperatures gradually recovered towards the end of the month, with some light rain patches affecting the territory on 30 November as a replenishment of the northeast monsoon reached the south China coastal areas.

     Four 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 1.2.  Monthly meteorological figures and departures from normal for November are tabulated in Table 2.
 

Warnings and Signals issued in November 2017

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
9 / 11 0200 9 / 11 1005
11 / 11 2140 12 / 11 0915
18 / 11 2110 19 / 11 1240


Table 1.2   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Red 3 / 11 1115 3 / 11 1900
Red 4 / 11 0945 5 / 11 2030
Yellow 26 / 11 1110 26 / 11 1800


Table 2   Figures and Departures from Normal - November 2017
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 24.4 degrees C 0.3 degree above normal
Mean Air Temperature 22.2 degrees C 0.4 degree above normal
Mean Daily Minimum Air Temperature 20.5 degrees C 0.7 degree above normal
Mean Dew Point Temperature 17.6 degrees C 1.6 degrees above normal
Mean Relative Humidity 76 % 5 % above normal
Mean Cloud Amount 74 % 20 % above normal
Total Rainfall 31.2 mm 6.4 mm below normal
Number of hours of Reduced VisibilityΔ 32 hours 98.3 hours below normal§
Total Bright Sunshine Duration 114.3 hours 65.8 hours below normal
Mean Daily Global Solar Radiation 10.62 Megajoule / square metre 1.66 Megajoule below normal
Total Evaporation 81.4 mm 18.1 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 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 November 2017

The percentile map of mean temperature of November 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 November 2017