Skip Content

The Weather of January 2009

    January 2009 was sunnier and drier than usual. The total bright sunshine duration for the month was 226.5 hours, about 60 percent above the normal figure of 141.7 hours. Only a trace of rainfall was recorded during the month, making it the driest January since 1994. The monthly mean temperature of 15.3 degrees was 0.8 degrees below normal.

    Under the influence of a strong winter monsoon, the weather was fine, dry and cold in the first three days of the year. The temperature rose a couple of degrees on 4 January as the winter monsoon weakened. The weather remained cool, fine and dry for the ensuing three days.

    A replenishment of the northeast monsoon brought cold and very dry conditions to the territory on 8 January. It stayed cold in the next eight days. The temperature recorded at Ta Kwu Ling fell to a minimum of -0.8 degrees on the morning of 11 January, the lowest since record began in 1985. Frost was reported at Ta Kwu Ling and Shatin on 11 January and Kau Sai Chau on 12 January.

    The weather stayed fine and dry from 17 to 19 January. Under the influence of a fresh to strong easterly airstream, the weather became mainly cloudy on 20 January. It turned sunny and warm the next day when the easterlies moderated. Under light wind conditions, it was hazy on 22 January.

    The cold air associated with an intense winter monsoon reached the south China coastal areas in the evening of 23 January bringing cloudy and rather cool weather to Hong Kong. It was generally cloudy and cold in the ensuing four days. With the moderation of the northeast monsoon, temperatures rose gradually during the next two days. It was generally fine for the last two 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 normal for January are tabulated in Table 2.


 

Warnings and Signals issued in January 2009


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
9 / 1 0445 9 / 1 1245
10 / 1 0145 10 / 1 0745


Table 1.2   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 31 / 12 1800 1 / 1 0600
Red 1 / 1 0600 3 / 1 0600
Yellow 3 / 1 0600 3 / 1 1100
Red 3 / 1 1100 4 / 1 0600
Yellow 4 / 1 0600 5 / 1 1800
Yellow 6 / 1 0603 6 / 1 1800
Yellow 7 / 1 0600 8 / 1 0600
Red 8 / 1 0600 15 / 1 0600
Yellow 15 / 1 0600 15 / 1 1130
Red 15 / 1 1130 16 / 1 1800
Yellow 16 / 1 1800 17 / 1 1115
Red 17 / 1 1115 17 / 1 1800
Yellow 17 / 1 1800 19 / 1 0600
Yellow 19 / 1 1315 19 / 1 1945
Yellow 22 / 1 0600 24 / 1 0600
Red 24 / 1 0600 25 / 1 1800
Yellow 25 / 1 1800 28 / 1 1800
Yellow 30 / 1 0600 30 / 1 1800


Table 1.3   Frost Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
9 / 1 1630 10 / 1 0745
10 / 1 1630 11 / 1 0845
12 / 1 1630 13 / 1 0730
13 / 1 1630 14 / 1 0735


Table 1.4   Cold Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
30 / 12 1620 3 / 1 1045
8 / 1 1620 16 / 1 0945
23 / 1 1630 28 / 1 1100


Table 2   Figures and Departures from Normal - January 2009

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 18.3 degrees C 0.3 degree below normal
Mean Air Temperature 15.3 degrees C 0.8 degree below normal
Mean Daily Minimum Air Temperature 13.0 degrees C 1.1 degrees below normal
Mean Dew Point Temperature 8.1 degrees C 2.9 degrees below normal
Mean Relative Humidity 64 % 9 % below normal
Mean Cloud Amount 40 % 20 % below normal
Total Rainfall Trace 24.9 mm below normal
Number of hours of Reduced VisibilityΔ 251 hours 13.1 hours above normal§
Total Bright Sunshine Duration 226.5 hours 84.8 hours above normal
Mean Daily Global Solar Radiation 14.13 Megajoule / square metre 3.58 Megajoule above normal
Total Evaporation 91.4 mm 10.7 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 2008
daily values of selected meteorological elements for HK for January 2009

Extract of Meteorological Observations in Hong Kong for January 2009