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  • The Weather of February 2018

  • 2 March 2018

    With the persistence of an intense winter monsoon during the early part of the month, the weather of February 2018 was overall cooler than usual. The monthly mean temperature of 16.0 degrees was 0.8 degree below the normal figure of 16.8 degrees. It was also relatively dry with only 4.5 millimetres of rainfall recorded in the month, less than 10 percent of the February normal of 54.4 millimetres. The accumulated rainfall for the first two months of the year was 66.7 millimetres, about 15 percent below the normal figure of 78.9 millimetres for the same period.

    An intense winter monsoon that started to affect the south China coastal areas in late January continued its dominance into the early part of February. Cold weather persisted till 8 February, with the lowest temperature of the month, 6.8 degrees, recorded at the Hong Kong Observatory on 1 February and frost being reported in places over the territory during the period as well. Following the arrival of a cold but dry continental airstream on 5 February, the initially cloudy conditions gave way to sunny skies the next day and daytime relative humidity dropped to 40 percent or below on 5 – 7 February.

    Apart from a couple of cloudy interludes on 7 and 9 February, generally fine weather persisted till 13 February. Temperatures started to climb during the period as the winter monsoon moderated, but a replenishment of northerly winds soon brought another cold snap on 12 February. Approaching the Chinese New Year festive period, the winter monsoon finally loosened its grip and moister air of maritime origin started to move in towards the south China coast. This led to increased cloudiness at first but as temperatures rose, a sunny and mild day greeted the first day of Chinese New Year on 16 February.

    After some morning fog on 17 February, a freshening easterly airstream brought cloudy and cooler weather to Hong Kong. As the easterly winds moderated, a warm maritime airstream returned to the coastal areas of Guangdong on 19 February and temperatures over most parts of the territory rose to 25 degrees or above on 20 February. Meanwhile, generally cloudy conditions persisted and with a replenishment of the winter monsoon coming down the coast of southeastern China, the weather in Hong Kong turned cooler again on 21 February. This was followed by the setting in of a fresh northerly airstream that brought overcast skies with rain patches and led to temperatures falling further over the next couple of days.

    As the winter monsoon subsided, two days of relatively mild and brighter weather followed on 24 and 25 February. Under the influence of a fresh easterly airstream, the weather then turned generally cloudy and cooler again the next day. As the easterly winds moderated, it became warm with sunny periods on 27-28 February. Temperatures at the Hong Kong Observatory climbed to the month’s highest of 26.2 degrees on the last day of the month.


Frost reported at Fanling on 6 February 2018
Frost reported at Fanling on 6 February 2018
(Photo courtesy of Miss Kwok (left) and Mr. Yip (right))


     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 1.4.  Monthly meteorological figures and departures from normal for February are tabulated in Table 2.
 

Warnings and Signals issued in February 2018

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
31 / 1 1600 1 / 2 0745


Table 1.2   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 1 / 2 0600 3 / 2 0600
Red 3 / 2 0600 7 / 2 0600
Yellow 7 / 2 0600 8 / 2 1900
Yellow 11 / 2 0600 11 / 2 2045
Red 12 / 2 0600 12 / 2 2230
Yellow 14 / 2 0720 14 / 2 2130


Table 1.3   Frost Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
3 / 2 1930 4 / 2 0745
4 / 2 1630 5 / 2 1130
5 / 2 1630 6 / 2 0915


Table 1.4   Cold Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
28 / 1 1200 8 / 2 1115
10 / 2 1620 13 / 2 0955


Table 2   Figures and Departures from Normal - February 2018
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 18.7 degrees C 0.2 degree below normal
Mean Air Temperature 16.0 degrees C 0.8 degree below normal
Mean Daily Minimum Air Temperature 13.9 degrees C 1.1 degrees below normal
Mean Dew Point Temperature 10.4 degrees C 2.6 degrees below normal
Mean Relative Humidity 70 % 10 % below normal
Mean Cloud Amount 73 % 1 % below normal
Total Rainfall 4.5 mm 49.9 mm below normal
Number of hours of Reduced VisibilityΔ 49 hours 82.3 hours below normal§
Total Bright Sunshine Duration 108.7 hours 14.5 hours above normal
Mean Daily Global Solar Radiation 11.50 Megajoule / square metre 2.11 Megajoule above normal
Total Evaporation 63.9 mm 4.0 mm above 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 2017

daily values of selected meteorological elements for HK for February 2018

The percentile map of mean temperature of February 2018

  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