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The Weather of February 2010

     The cold snap during the Chinese New Year period was more than counter-balanced by a persistently warm and humid maritime airstream towards the end of the month, making February 2010 wetter and milder than usual.  The mean temperature for the month was 17.9 degrees, about 1.6 degrees above normal.  The monthly mean relative humidity of 88 percent was about 10 percent above normal, the highest since 1959.  The month was also gloomier than usual.  The total bright sunshine duration of 31.8 hours was only about one-third of the normal figure of 93.8 hours, the smallest since 1985.  The total rainfall in the month was 113.1 millimetres, more than double the normal figure of 52.3 millimetres. 

     With a warm maritime airstream prevailing over the coastal areas of Guangdong, it was foggy in Hong Kong for the first day of the month.  A fresh northeast monsoon arrived at the south China coastal areas on 2 February, bringing cooler weather with fog and light rain patches to the territory.  Local weather remained cloudy with mist and light rain for the ensuing four days. 

     Under the influence of an unstable airstream, it was overcast with periods of rain on 7 and 8 February.  A total of 94.1 millimeters of rainfall was recorded at the Hong Kong Observatory on 7 February, the highest daily rainfall for February on record.  Affected by a warm and humid maritime airstream, it was warm with coastal mist and fog from 9 to 11 February.  The daily minimum and mean temperatures recorded at the Hong Kong Observatory on 11 February were 23.9 degrees and 25.0 degrees respectively, both the highest for February on record.

     Meanwhile, a cold front had formed over central China, and moved southwards steadily over inland Guangdong.  It crossed the coastal areas on the morning of 12 February.  Affected by the intense northeast monsoon behind the cold front, local temperatures fell significantly from about 25 degrees at first to around 12 degrees by midnight.  It remained cold and windy with a few rain patches the next day.  Despite the weakening of the northeast monsoon, local weather remained cool with fog and a few rain patches on 14 February. 

     The northeast monsoon over south China intensified significantly on 15 February and brought cold and rainy weather to the territory for the ensuing six days.  The temperatures recorded at the Hong Kong Observatory dropped to a minimum of 7.7 degrees on 19 February, the lowest of the month. 

     The northeast monsoon over the coastal areas of Guangdong moderated and replaced by a humid easterly airstream on 21 February.  Local temperatures started to rise on that day.  It was rather mild with mist from 21 to 24 February.  With a maritime airstream prevailing, it was foggy with local temperature and relative humidity rising further for the last four days of the month.

    There was no tropical cyclone 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 normals for February are tabulated in Table 2.
 

Warnings and Signals issued in February 2010


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
13 / 2 2200 14 / 2 0445


Table 1.2   Thunderstorm Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
7 / 2 0225 7 / 2 0400
7 / 2 0706 7 / 2 0830
7 / 2 1140 7 / 2 1500
7 / 2 1740 7 / 2 1945


Table 1.3   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 21 / 2 1130 21 / 2 1800


Table 1.4   Cold Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
12 / 2 1620 13 / 2 1620
14 / 2 1620 20 / 2 1200


Table 2   Figures and Departures from Normal - February 2010

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 19.7 degrees C 1.1 degrees above normal
Mean Air Temperature 17.9 degrees C 1.6 degrees above normal
Mean Daily Minimum Air Temperature 16.3 degrees C 1.9 degrees above normal
Mean Dew Point Temperature 15.8 degrees C 3.6 degrees above normal
Mean Relative Humidity 88 % 10 % above normal
Mean Cloud Amount 88 % 15 % above normal
Total Rainfall 113.1 mm 60.8 mm above normal
Number of hours of Reduced VisibilityΔ 93 hours 52.1 hours below normal§
Total Bright Sunshine Duration 31.8 hours 62.0 hours below normal
Mean Daily Global Solar Radiation 6.32 Megajoule / square metre 3.29 Megajoule below normal
Total Evaporation 38.5 mm 29.1 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 1971 - 2000 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2009
daily values of selected meteorological elements for HK for February 2010

Extract of Meteorological Observations in Hong Kong for February 2010