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The Weather of September 2002

    September was much wetter than usual.  The monthly rainfall of 723.0 millimetres was about 2.4 times the normal amount and ranked the fourth highest for the month.  The accumulated rainfall since 1 January amounted to 2203.6 millimetres, about 10 per cent higher than the normal figure of 2007.1 millimetres for the same period.

    The weather in the first three days of September was mainly fine apart from a few isolated showers.   With the establishment of an anticyclone over China, the weather became fine and dry with long sunny periods for the next six days.   The continental air brought hazy conditions on 6 September and the visibility dropped to below 2000 metres inside the harbour.

    On 10 September, Hagupit developed as a tropical depression over the northern part of the South China Sea about 460 kilometres southeast of Hong Kong.   It intensified rapidly into a severe tropical storm as it moved west-northwest towards the coast of western Guangdong, necessitating the issuance of the number 8 tropical cyclone warning signal in Hong Kong for the first time this year.  Hagupit was closest to Hong Kong in the afternoon of 11 September, and landed near Yangjiang in the early hours of 12 September.  During the passage of Hagupit, a total of 32 persons in Hong Kong were injured.  Thirty seven fishermen in three fishing boats were in danger and were lifted to safety by a helicopter of the Government Flying Service.

    After making landfall, Hagupit weakened into an area of low pressure over Guangxi on 13 September.  As this area of low pressure drifted back towards the east, it brought several days of heavy rain and thunderstorms to Hong Kong.  The Red Rainstorm Warning was issued on 15 September for the first time this year.   The daily rainfall exceeded 100 millimetres for three consecutive days from 15 to 17 September, and the corresponding 3-day rainfall of 445.8 millimetres was the highest on record for September.

    The weather improved on 18 September as a continental airstream reached the south China coast.  Sunny weather continued for the next three days.  Although it was mainly fine during the day on Mid-Autumn Festival, the weather deteriorated in the late evening with frequent thunderstorms and heavy rain overnight.  The eastern part of the territory was worse hit by the downpour.

    Rain stopped on 23 September but the outer rainband of Tropical Storm Mekkhala off the coast of Vietnam brought overcast weather and rain to Hong Kong again on 24 and 25 September.  The weather improved on 26 September but it remained partly cloudy with a few showers for the remainder of the month.

    A total of 7 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 1.7.  Monthly meteorological figures and departures from normal for September are tabulated in Table 2.


 

Warnings and Signals issued in September 2002


Table 1.1   Tropical Cyclone Warning Signals

Name of
Tropical Cyclone		 Signal
Number		 Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Hagupit 1 10 / 9 1440 11 / 9 0540
3 11 / 9 0540 11 / 9 1340
8 SE 11 / 9 1340 12 / 9 0140
3 12 / 9 0140 12 / 9 0540

 

Table 1.2   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
19 / 9 2245 20 / 9 0440

 

Table 1.3   Rainstorm Warning Signals

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 14 / 9 2110 15 / 9 0330
Red 15 / 9 0330 15 / 9 0615
Amber 15 / 9 0615 15 / 9 0955
Amber 16 / 9 2330 17 / 9 0430
Amber 17 / 9 1805 17 / 9 2100

 

Table 1.4   Landslip Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
15 / 9 0345 15 / 9 2030
17 / 9 0130 17 / 9 1245

 

Table 1.5   Thunderstorm Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 9 1705 1 / 9 1805
2 / 9 0825 2 / 9 0925
2 / 9 1050 2 / 9 1250
3 / 9 1050 3 / 9 1430
3 / 9 1515 3 / 9 1915
10 / 9 1520 10 / 9 2230
12 / 9 1040 12 / 9 1140
13 / 9 1155 13 / 9 1415
14 / 9 0910 14 / 9 1110
14 / 9 1920 15 / 9 1830
15 / 9 1930 16 / 9 0530
16 / 9 1215 17 / 9 0530
17 / 9 0740 17 / 9 1040
17 / 9 1300 17 / 9 2100
17 / 9 2300 18 / 9 0500
22 / 9 0040 22 / 9 0900

 

Table 1.6   Fire Danger Warnings

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 20 / 9 1200 22 / 9 0140

 

Table 1.7   Very Hot Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
6 / 9 0730 7 / 9 1630

 
 

Table 2   Figures and Departures from Normal - September 2002

Meteorological Element Figure of the Month Departure from Normal
Mean Daily Maximum Air Temperature 29.1 degrees C 1.2 degrees below normal
Mean Air Temperature 27.2 degrees C 0.4 degree below normal
Mean Daily Minimum Air Temperature 25.5 degrees C normal
Mean Dew Point Temperature 23.3 degrees C normal
Mean Relative Humidity 80 % 2 % above normal
Mean Cloud Amount 71 % 8 % above normal
Total Rainfall 723.0 mm 423.3 mm above normal
Total Bright Sunshine Duration 146.1 hours 35.6 hours below normal
Mean Daily Global Solar Radiation 12.99 Megajoule / square metre 3.50 Megajoule below normal
Total Evaporation 113.9 mm 36.4 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.

 
daily values of selected meteorological elements for HK for September 2002

Extract of Meteorological Observations in Hong Kong for September 2002