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The Weather of January 2005

    With haze occurring on most days in Hong Kong in the month, the number of hours of reduced visibility observed at the Hong Kong International Airport reached 476 hours (i.e. 64% of the time) in January 2005. January 2005 was drier than normal. The monthly rainfall of 5.9 millimetres was 17.5 millimetres below normal.

    An intense surge of the winter monsoon brought fine, dry and very cold weather to Hong Kong on the first day of January. The minimum temperature of 6.4 degrees that morning was the third lowest on record for New Year's Day. While remaining cold, it turned cloudy on 2 and 3 January. With the weakening of the winter monsoon, temperatures climbed gradually in the next three days. The weather turned fine on 6 January. Apart from some cloudy periods on 8 January, generally fine weather prevailed until 12 January. There were also long periods of haze from 4 to 12 January.

    Another intense cold surge arrived at the south China coast on the early morning of 13 January, bringing cloudy and rainy weather to Hong Kong. It got progressively colder during the day with temperatures in the urban area falling to about 10 degrees that evening. The temperature dropped further to about 7 degrees in the morning of 14 January. Ice pellets and icicles were reported on Tai Mo Shan where the temperature fell to a minimum of -2.1 degrees that morning. The clouds dispersed during the day and there was plenty of sunshine. The weather remained fine and cold on 15 and 16 January. As local winds moderated, it became hazy again in the following three days. The visibility at the Hong Kong International Airport once dropped below 3000 metres on 19 January.

    It became cloudy with some mist patches on 20 January when a replenishment of the winter monsoon arrived at the south China coast. On 21 and 22 January, it was mainly cloudy with some light rain patches in the morning.

    Under the influence of a maritime airstream, it was humid with mist and fog in Hong Kong from 23 to 30 January. On the night of 25 January, two cargo ships collided near Lei Yue Mun in thick fog.

    A cold front crossed the south China coast on the night of 30 January, bringing some light rain and cooler weather to Hong Kong. It was cold with some rain on the last day of the month.

    Only one tropical cyclone occurred in 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 2005


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
30 / 12 1800 1 / 1 0845
14 / 1 0945 14 / 1 1330


Table 1.2   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Red 31 / 12 1300 3 / 1 0600
Red 4 / 1 0600 4 / 1 1800
Yellow 8 / 1 1800 10 / 1 0600
Red 14 / 1 0600 17 / 1 0600
Yellow 23 / 1 1145 23 / 1 1800


Table 1.3   Frost Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
31 / 12 1630 1 / 1 0945
14 / 1 1630 15 / 1 0705


Table 1.4   Cold Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
28 / 12 1315 2 / 1 1630
2 / 1 2355 3 / 1 1130
12 / 1 1630 17 / 1 1130
30 / 1 2325 3 / 2 1615


Table 2   Figures and Departures from Normal - January 2005

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 17.9 degrees C 0.7 degree below normal
Mean Air Temperature 15.9 degrees C 0.1 degree above normal
Mean Daily Minimum Air Temperature 14.2 degrees C 0.6 degree above normal
Mean Dew Point Temperature 11.3 degrees C 1.1 degrees above normal
Mean Relative Humidity 75 % 4 % above normal
Mean Cloud Amount 63 % 5 % above normal
Total Rainfall 5.9 mm 17.5 mm below normal
Number of hours of Reduced VisibilityΔ 476 hours 298.4 hours above normal§
Total Bright Sunshine Duration 141.7 hours 10.7 hours below normal
Mean Daily Global Solar Radiation 9.63 Megajoule / square metre 2.00 Megajoule below normal
Total Evaporation 64.1 mm 33.4 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 1961-1990 climatological normal, except for number of hours of reduced visibility.
  §   Departure from mean value between 1997 and 2004.
daily values of selected meteorological elements for HK for January 2005

Extract of Meteorological Observations in Hong Kong for January 2005