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The Weather of October 2006

    October 2006 was unseasonably warm. Both the monthly mean temperature of 26.4 degrees and the mean daily minimum temperature of 24.7 degrees equaled the records set in 1983. The month was also rather dry with only 31.2 millimetres of rainfall, about 78 percent below normal. The accumulated rainfall since the beginning of the year is 2498.3 millimetres, about 16 percent above the normal figure of 2151.9 millimetres for the same period. October 2006 was also hazy with 482 hours of reduced visibility observed at the Hong Kong International Airport.

    Under the influence of the northeast monsoon, it was cloudy with light rain patches on the first two days of the month. A ridge of high pressure over southeastern China brought generally fine weather to the territory on 3 October. The weather remained generally fine on the next five day.

    The weather turned cloudy with some rain on 9 October when a cloud band covered southern China. The clouds thinned out and there were sunny periods on the next day. It was sunny from 11 to 13 October.

    An easterly airstream affected the south China coast on 14 October, bringing a few showers to the territory. The weather stayed cloudy with some showers in the ensuing two days. With a ridge of high pressure building up over southeastern China, the weather improved on 17 October. Apart from some hazy episodes, mainly fine weather continued for the following six days.

    A fresh northeast monsoon reached the south China coast on 24 October. The weather turned cloudy with a few rain patches. Sunshine returned on 25 October. Under the influence of a continental airstream, it was mainly fine with some haze for the rest of the month.

    Five tropical cyclones occurred in the western North Pacific and the South China Sea in the month. An overview of the tropical cyclones is presented in "Tropical Cyclones Reports and Publications" webpage.

    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 October are tabulated in Table 2.


 

Warnings and Signals issued in October 2006

Table 1.1   Tropical Cyclone Warning Signals
Name of
Tropical Cyclone		 Signal
Number		 Beginning Time Ending Time
Day/Month HKT Day/Month HKT
CIMARON 1 31 / 10 1420 3 /11 1330


Table 1.2   Thunderstorm Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
16 / 10 0515 16 / 10 0630


Table 1.3   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 2 / 10 0600 2 / 10 1800
Yellow 6 / 10 0600 7 / 10 1315
Red 7 / 10 1315 7 / 10 1800
Yellow 7 / 10 1800 8 / 10 1800
Yellow 22 / 10 0600 22 / 10 1800
Yellow 28 / 10 0600 30 / 10 2305
Red 31 / 10 1100 4 /11 0600


Table 2   Figures and Departures from Normal - October 2006
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 29.0 degrees C 1.1 degrees above normal
Mean Air Temperature 26.4 degrees C 1.2 degrees above normal
Mean Daily Minimum Air Temperature 24.7 degrees C 1.6 degrees above normal
Mean Dew Point Temperature 21.8 degrees C 2.0 degrees above normal
Mean Relative Humidity 77 % 4 % above normal
Mean Cloud Amount 64 % 8 % above normal
Total Rainfall 31.2 mm 113.6 mm below normal
Number of hours of Reduced Visibility 482 hours 367.0 hours above normal§
Total Bright Sunshine Duration 195.8 hours 0.8 hour above normal
Mean Daily Global Solar Radiation 14.31 Megajoule / square metre 1.15 Megajoule below normal
Total Evaporation 113.2 mm 39.0 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.

 

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 2005.
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