The Weather of August 2006

August 2006 was drier than usual. The total rainfall of 275.4 millimetres was 30 per cent below normal. However, with above normal rainfall in the past four months, the accumulated rainfall since 1 January was 2046.9 millimetres, 20 per cent above the normal figure of 1707.4 millimetres for the same period.

Under the influence of a ridge of high pressure over southeastern China, it was fine and hot on the first day of the month. Meanwhile, Tropical Storm Prapiroon entered the South China Sea and moved west-northwestwards towards the western coast of Guangdong. Prapiroon intensified into a Typhoon on 2 August and made landfall over east of Zhanjiang on the night of 3 August. With the approach of Prapiroon, winds over the harbour area strengthened subsequently on 2 and 3 August. The outer rainbands of Prapiroon also brought squally heavy showers to the territory. During the inclement weather, a number of containers at Kwai Chung and Tuen Mun were blown down, leading to one injury. Another seven people were wounded by fallen objects and about seven hundred trees were blown down. Local winds weakened gradually on 4 August. Showery weather persisted from 4 to 6 August.

The weather turned fine on 7 August. On 8 August, there were sunny periods. It was hot and hazy on 9 August when Tropical Storm Bopha skirted across southern Taiwan and edged towards the coastal waters of eastern Guangdong. There were squally thunderstorms on the early morning of 10 August.

Fine weather returned on 11 August. It remained fine and hot in the following seven days. There were a few heavy showers and squally thunderstorms on 19 and 20 August. On the afternoon of 20 August, a man was swept away and drowned by flash floods in Tai Shing stream, Tsuen Wan and four maintenance workers were injured by lightning in the Hong Kong International Airport.

It was fine and hot from 21 to 23 August. A tropical depression over the northern part of the South China Sea brought scattered showers to the territory on 24 August. The weather stayed showery in the ensuing four days.

It was fine and hot on the last three days of the month.

Eight 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 1.3. Monthly meteorological figures and departures from normal for August are tabulated in Table 2.

Warnings and Signals issued in August 2006

Table 1.1 Tropical Cyclone Warning Signals

Name of Tropical Cyclone	Signal Number	Beginning Time		Ending Time
Name of Tropical Cyclone	Signal Number	Day/Month	HKT	Day/Month	HKT
PRAPIROON	1	1 / 8	1210	2 / 8	1620
	3	2 / 8	1620	4 / 8	0540
	1	4 / 8	0540	4 / 8	1540
BOPHA	1	9 / 8	0840	10 / 8	2210
no name	1	24 / 8	1110	25 / 8	0620

Table 1.2 Rainstorm Warning Signals

Colour	Beginning Time		Ending Time
Colour	Day/Month	HKT	Day/Month	HKT
Amber	10 / 8	0010	10 / 8	0140
Amber	19 / 8	0020	19 / 8	0140

Table 1.3 Thunderstorm Warning

Beginning Time		Ending Time
Day/Month	HKT	Day/Month	HKT
2 / 8	0440	2 / 8	0600
5 / 8	0403	5 / 8	0700
5 / 8	0950	5 / 8	1100
6 / 8	0440	6 / 8	0800
8 / 8	1350	8 / 8	1500
9 / 8	1655	10 / 8	0600
18 / 8	2300	19 / 8	0430
20 / 8	1215	20 / 8	1600
24 / 8	1025	24 / 8	1430
24 / 8	1700	24 / 8	2000
24 / 8	2200	25 / 8	0815
25 / 8	1240	25 / 8	1500
25 / 8	1555	25 / 8	1700
25 / 8	1750	26 / 8	0810
27 / 8	0445	27 / 8	0600
28 / 8	0230	28 / 8	0600
28 / 8	1030	28 / 8	1510
28 / 8	1700	28 / 8	2100

Table 2 Figures and Departures from Normal - August 2006

Meteorological Element	Figure of the Month	Departure from Normal*
Mean Daily Maximum Air Temperature	30.8 degrees C	0.5 degree below normal
Mean Air Temperature	28.3 degrees C	0.1 degree below normal
Mean Daily Minimum Air Temperature	26.5 degrees C	0.2 degree above normal
Mean Dew Point Temperature	25.1 degrees C	0.3 degree above normal
Mean Relative Humidity	83 %	2 % above normal
Mean Cloud Amount	68 %	2 % above normal
Total Rainfall	275.4 mm	116.0 mm below normal
Number of hours of Reduced VisibilityΔ	92 hours	33.8 hours above normal§
Total Bright Sunshine Duration	213.2 hours	6.2 hours above normal
Mean Daily Global Solar Radiation	17.15 Megajoule / square metre	0.46 Megajoule below normal
Total Evaporation	133.5 mm	23.4 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.
	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.

daily values of selected meteorological elements for HK for August 2006

Extract of Meteorological Observations in Hong Kong for August 2006