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The Weather of February 2011

     February 2011 was marked by mostly sunny and mild weather interrupted by a cold and cloudy spell with some rain.  The month ended up with a mean temperature of 16.2 degrees, just 0.1 degrees below normal.  The total bright sunshine duration in the month was 127.7 hours, 33.9 hours above normal.  With the abundance sunshine, the monthly mean daily maximum temperature was 19.1 degrees, 0.5 degrees above the normal figure of 18.6 degrees.

     February 2011 was also drier than usual.  The total rainfall in the month was 23.7 millimetres, only about 45 percent of the normal figure.

     After experiencing generally cold and dry condition for the first two days of the month, Hong Kong enjoyed mainly fine and dry weather apart from some haze and mist for the ensuing eight days, as a result of a ridge of high pressure dominated over southern China.  With abundant sunshine, local temperatures soared up to above 20 degrees during the day from 4 to 10 February.
 
     Meanwhile, a cold front formed over southern China on 10 February and crossed the coastal areas of Guangdong the next day.  Under the influence of the winter monsoon behind the cold front, local weather turned cooler with mist and a few rain patches on 11 and 12 February.  With strengthening of the winter monsoon, it was cold with rain for the next four days.  The temperature at the Hong Kong Observatory fell to a minimum of 8.6 degrees on 14 February, the lowest of the month.

     Affected by a humid easterly airstream, the weather became cloudy with fog on 17 February.  The visibility fell below 1000 metres in the harbour and was around 100 metres at Waglan Island that morning.  A replenishment of the northeast monsoon reached the south China coastal areas on 18 February.  Local weather became rather cool with rain patches from 18 to 21 February. 

     Under the influence of a dry northeasterly airstream, the weather became dry with some sunny periods on 22 and 23 February.  Apart from some mist, it was mainly fine with warm afternoons in Hong Kong from 24 to 27 February.  Affected by a maritime airstream, it was sunny with fog in the last day of the month.  With plenty of sunshine, the temperature recorded at the Hong Kong Observatory rose to a maximum of 26.9 degrees on 28 February, the highest 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 1.3.  Monthly meteorological figures and departures from normal for February are tabulated in Table 2.

 

Warnings and Signals issued in February 2011


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
15 / 2 0605 15 / 2 1245


Table 1.2   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 1 / 2 0600 1 / 2 1803
Yellow 2 / 2 0600 2 / 2 1200
Red 2 / 2 1200 2 / 2 2245
Yellow 3 / 2 0600 6 / 2 1100
Red 6 / 2 1100 6 / 2 2100
Yellow 7 / 2 0600 7 / 2 2315
Yellow 22 / 2 0600 22 / 2 2230
Yellow 23 / 2 0600 23 / 2 2100
Yellow 26 / 2 0600 26 / 2 1800


Table 1.3   Cold Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
28 / 1 1620 3 / 2 0945
11 / 2 1620 16 / 2 1620
19 / 2 1145 21 / 2 0745


Table 2   Figures and Departures from Normal - February 2011

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 19.1 degrees C 0.5 degree above normal
Mean Air Temperature 16.2 degrees C 0.1 degree below normal
Mean Daily Minimum Air Temperature 14.2 degrees C 0.2 degree below normal
Mean Dew Point Temperature 12.0 degrees C 0.2 degree below normal
Mean Relative Humidity 77 % 1 % below normal
Mean Cloud Amount 65 % 8 % below normal
Total Rainfall 23.7 mm 28.6 mm below normal
Number of hours of Reduced VisibilityΔ 201 hours 59.6 hours above normal§
Total Bright Sunshine Duration 127.7 hours 33.9 hours above normal
Mean Daily Global Solar Radiation 11.47 Megajoule / square metre 1.86 Megajoule above normal
Total Evaporation 68.4 mm 0.8 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 1971 - 2000 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2010

daily values of selected meteorological elements for HK for February 2011

Extract of Meteorological Observations in Hong Kong for February 2011