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The Weather of June 2009

    June 2009 was drier than usual. The total rainfall of 341.8 millimetres in the month was about 12 percent below the normal figure of 388.1 millimetres. The accumulated rainfall since 1 January was 817.5 millimetres, about 22 percent below the normal figure of 1054.7 millimetres for the same period. The mean temperature was 28.1 degrees, 0.2 degrees above the normal figure of 27.9 degrees.

    A ridge of high pressure brought mainly fine weather to Hong Kong on the first day of the month. Under the influence of a southerly airstream over the coastal areas of Guangdong, the weather turned cloudy with isolated showers on 2 June. At the same time, a trough of low pressure developed over the northern part of southern China and moved south gradually. It brought heavy rain and squally thunderstorms to the territory on 3 and 4 June. More than 70 millimetres of rainfall were recorded over parts of the New Territories on the morning of 4 June. With the westward extension of the Pacific ridge, local weather turned fine in the afternoon of 4 June. It remained sunny and hot from 5 to 7 June. The temperature at the Hong Kong Observatory rose to a maximum of 32.9 degrees on 6 June, the highest of the month.

    A humid maritime airstream dominated over the coastal areas of Guangdong and brought cloudy and showery weather to Hong Kong for the ensuing three days. Affected by an active trough of low pressure over southern China, local weather deteriorated further with occasional rain and squally thunderstorms from 11 to 16 June. A ridge of high pressure developed over southern China on 17 June, bringing fine and hot weather to Hong Kong on that day.

    Affected by the subsidence airmass associated with Severe Tropical Storm Linfa over the northern part of the South China Sea, local weather remained sunny and hot apart from a few isolated showers from 18 to 21 June. After Linfa made landfall over Fujian on the night of 21 June, an active southwesterly airstream prevailed over the coastal areas of southern China and brought thundery showers to Hong Kong from 22 to 24 June.

    Tropical Storm Nangka entered the South China Sea on the evening of 24 June and edged towards the coast of eastern Guangdong in the next two days. Nangka made landfall over the vicinity of Daya Bay and weakened into an area of low pressure inland Guangdong in the morning of 27 June. Locally, it was mainly cloudy with showers on 25 and 26 June. Affected by the remnants of Nangka, the weather was cloudy with heavy rain and a few squally thunderstorms on 27 and 28 June. The heavy rain eased off and there were sunny periods on 29 June. A ridge of high pressure brought mainly fine and hot weather to the territory on 30 June.

   
   Two 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 1.5.  Monthly meteorological figures and departures from normal for June are tabulated in Table 2.
 

Warnings and Signals issued in June 2009


Table 1.1   Tropical Cyclone Warning Signals

Name of
Tropical Cyclone		 Signal
Number		 Beginning Time Ending Time
Day/Month HKT Day/Month HKT
LINFA 1 20 / 6 1040 21 / 6 0545
NANGKA 1 26 / 6 0715 26 / 6 1540
3 26 / 6 1540 27 / 6 0525


Table 1.2   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
27 / 6 1140 27 / 6 1800


Table 1.3   Rainstorm Warning Signals

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 4 / 6 0020 4 / 6 0110
Red 4 / 6 0110 4 / 6 0210
Amber 4 / 6 0210 4 / 6 0335
Amber 11 / 6 0615 11 / 6 0840
Amber 12 / 6 1025 12 / 6 1145


Table 1.4   Thunderstorm Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
3 / 6 0915 3 / 6 1330
3 / 6 2330 4 / 6 0530
8 / 6 1725 8 / 6 1900
8 / 6 2100 9 / 6 0200
9 / 6 0615 9 / 6 0815
9 / 6 1020 9 / 6 1500
10 / 6 1230 10 / 6 1530
11 / 6 0345 11 / 6 1300
11 / 6 1815 11 / 6 1945
12 / 6 0920 12 / 6 1300
13 / 6 1645 13 / 6 1745
13 / 6 1955 13 / 6 2200
14 / 6 0055 14 / 6 0500
14 / 6 0710 14 / 6 1530
14 / 6 2205 15 / 6 0600
15 / 6 0750 15 / 6 0900
15 / 6 1805 15 / 6 2015
15 / 6 2310 16 / 6 0930
16 / 6 1040 16 / 6 1500
19 / 6 0635 19 / 6 1345
20 / 6 1620 20 / 6 1800
21 / 6 0410 21 / 6 0740
22 / 6 0705 22 / 6 0830
22 / 6 0900 22 / 6 1500
22 / 6 1600 22 / 6 1945
23 / 6 0735 23 / 6 0900
23 / 6 1230 23 / 6 1830
23 / 6 2200 24 / 6 1300
25 / 6 1120 25 / 6 1400
26 / 6 2355 27 / 6 0600
27 / 6 1005 27 / 6 1600
27 / 6 2325 28 / 6 0600
28 / 6 1120 28 / 6 2015
30 / 6 0350 30 / 6 0615


Table 1.5   Special Announcement on Flooding
in the Northern New Territories

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
4 / 6 0050 4 / 6 0300


Table 2   Figures and Departures from Normal - June 2009

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 30.7 degrees C 0.3 degree above normal
Mean Air Temperature 28.1 degrees C 0.2 degree above normal
Mean Daily Minimum Air Temperature 26.2 degrees C 0.1 degree above normal
Mean Dew Point Temperature 24.6 degrees C normal
Mean Relative Humidity 81 % 1 % below normal
Mean Cloud Amount 76 % normal
Total Rainfall 341.8 mm 46.3 mm below normal
Number of hours of Reduced VisibilityΔ 8 hours 14.1 hours below normal§
Total Bright Sunshine Duration 127.1 hours 31.2 hours below normal
Mean Daily Global Solar Radiation 14.06 Megajoule / square metre 1.25 Megajoule below normal
Total Evaporation 118.5 mm 10.5 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 1971 - 2000 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2008
daily values of selected meteorological elements for HK for June 2009

Extract of Meteorological Observations in Hong Kong for June 2009