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 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 1.2. Monthly meteorological figures and departures from normal for November are tabulated in Table 2.
|Beginning Time||Ending Time|
|9 / 11||0200||9 / 11||1005|
|11 / 11||2140||12 / 11||0915|
|18 / 11||2110||19 / 11||1240|
|Colour||Beginning Time||Ending Time|
|Red||3 / 11||1115||3 / 11||1900|
|Red||4 / 11||0945||5 / 11||2030|
|Yellow||26 / 11||1110||26 / 11||1800|
|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.
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.
* Departure from 1981 - 2010 climatological normal, except for number of hours of reduced visibility
§ Departure from mean value between 1997 and 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