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The Weather of November 2007

    November 2007 was cooler and drier than usual. The mean temperature of 20.9 degrees was 0.5 degrees below normal. The total rainfall in the month was only 3.9 millimetres, about 11% of the normal figure of 35.1 millimeters. The accumulated rainfall since the beginning of the year was 1691.2 millimetres, about 23 percent below the normal figure of 2187 millimetres for the same period.

    An intense northeast monsoon and a rainband over southern China brought cool and rainy weather to Hong Kong on the first two days of the month. There were sunny periods on 3 November when the rainband dissipated. Under the influence of the northeast monsoon, it was sunny and dry in the ensuing three days.

    The weather turned cloudy on 8 November as the cloud band associated with Tropical Storm Peipah over the South China Sea reached the south China coast. Clouds dispersed on 9 November and the weather turned fine again. Apart from some haze on 18 and 19 November, generally fine weather persisted in the next sixteen days.

    The northerlies strengthened on 26 November when a surge of the intense northeast monsoon reached southern China. In the ensuing three days, the weather became progressively cooler and very dry with the relative humidity falling below 40 percent in most places. Under windy and dry conditions, there were 16 reports of hill fire on 27 November. Temperatures dropped to 13.7 degrees on 28 November, the lowest in the month.

    The weather stayed fine and dry on the last day of the month.

    Four tropical cyclones occurred in the western North Pacific and the South China Sea in the month.

    Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.2.  Monthly meteorological figures and departures from normal for November are tabulated in Table 2.


 

Warnings and Signals issued in November 2007


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 11 1615 2 / 11 0745
26 / 11 1930 27 / 11 1245
28 / 11 0245 28 / 11 0945


Table 1.2   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 3 / 11 0600 4 / 11 0600
Red 4 / 11 0600 4 / 11 2315
Red 5 / 11 0542 8 / 11 0600
Red 9 / 11 1230 10 / 11 0600
Yellow 10 / 11 0600 12 / 11 0600
Red 12 / 11 1315 12 / 11 1800
Yellow 18 / 11 0600 19 / 11 0600
Red 19 / 11 0600 20 / 11 1800
Red 21 / 11 1145 21 / 11 2030
Red 22 / 11 1145 22 / 11 1800
Red 23 / 11 1145 24 / 11 1800
Yellow 24 / 11 1800 26 / 11 0600
Red 26 / 11 0600 1 / 12 0600


Table 2   Figures and Departures from Normal - November 2007

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 23.8 degrees C 0.4 degree below normal
Mean Air Temperature 20.9 degrees C 0.5 degree below normal
Mean Daily Minimum Air Temperature 18.7 degrees C 0.5 degree below normal
Mean Dew Point Temperature 13.5 degrees C 1.7 degrees below normal
Mean Relative Humidity 64 % 5 % below normal
Mean Cloud Amount 54 % 1 % above normal
Total Rainfall 3.9 mm 31.2 mm below normal
Number of hours of Reduced VisibilityΔ 171 hours 17.3 hours above normal§
Total Bright Sunshine Duration 227.0 hours 45.5 hours above normal
Mean Daily Global Solar Radiation 14.50 Megajoule / square metre 1.11 Megajoule above normal
Total Evaporation 115.0 mm 14.1 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.


 

The calibration factors of the pyranometer at King's Park in 2006 and 2007 have been re-computed based on the results of a regional instrument comparison in Asia in 2007. The readings of total global solar radiation at King's Park in 2006 and 2007 displayed in this web page before 13 June 2008 have been revised on 13 June 2008 using the new calibration factors.

  *   Departure from 1961-1990 climatological normal, except for number of hours of reduced visibility.

  §   Departure from mean value between 1997 and 2006


daily values of selected meteorological elements for HK for November 2007

Extract of Meteorological Observations in Hong Kong for November 2007