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The Weather of June 2010

     June 2010 was gloomier and wetter than usual.  The total bright sunshine duration was 92.5 hours, only 58 percent of the normal figure of 158.3 hours and the 6th lowest on record.  The accumulated total bright sunshine duration since 1 January was 504.4 hours, about 30 percent below the normal figure of 723.8 hours for the same period, the lowest on record. The total rainfall in the month was 474.9 millimetres, about 22 percent above the normal figure of 388.1 millimetres.  The accumulated rainfall since 1 January was 885.6 millimetres, about 16 percent below the normal figure of 1054.7 millimetres for the same period.  Due to gloomier and wetter weather, June 2010 was also cooler than usual.  The mean temperature for the month was 27.1 degrees, about 0.8 degrees below normal.

     Under the combined effect of a rather strong northeast monsoon over the south China coastal areas and a trough of low pressure over the northern part of the South China Sea, it was relatively cool with rain for the first three days of the month.  The minimum temperature recorded at the Hong Kong Observatory on 2 June was 20.4 degrees, the lowest in June since 1964.  Rain eased off with the moderation of the northeast monsoon on 4 June.  The weather turned fine apart from a few showers on 5 June when a ridge of high pressure established over the coast of southeast China.  Weather remained generally fine for the ensuing three days.  

     With the approach of a trough of low pressure to the coast of Guangdong, local weather became unsettled with some heavy rain and a few squally thunderstorms on 9 to 10 June.  The rain eased off with sunny intervals on 11 and 12 June when the trough of low pressure left the coast and moved to the northern part of the South China Sea.  The trough of low pressure shifted back towards the coast of Guangdong on 13 and 14 June, bringing squally thunderstorms to the territory.  With the trough of low pressure lingering over the coastal areas of Guangdong, local weather remained cloudy with showers for the following two days.

     Affected by the southwest monsoon, the weather was hot with sunny periods apart from a few isolated showers from 17 to 22 June.  The southwest monsoon became active on 23 and 24 June, bringing thundery showers to the territory.  The rain eased off on 25 June.  Meanwhile, an active trough of low pressure developed over southern China and moved to the coastal areas of Guangdong, giving rise to heavy rain and squally thunderstorms from 26 to 28 June.  The rain was particularly heavy and persistent on 26 June with more than 150 millimeters of rainfall recorded in Kowloon and over parts of the Lantau Island.  With the westward extension of a ridge of high pressure over the Pacific, local weather became stable with sunny periods on 29 June.  It was mainly fine and hot for the last day of the month.  The temperatures recorded at the Hong Kong Observatory rose to a maximum of 32.7 degrees during the day, the highest of the month. 

    There was no tropical cyclone over the South China Sea and the western North Pacific 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 June are tabulated in Table 2. 
   

Warnings and Signals issued in June 2010


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
2 / 6 0745 2 / 6 1630


Table 1.2   Rainstorm Warning Signals

Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 10 / 6 0510 10 / 6 0625
Amber 26 / 6 0358 26 / 6 0530
Amber 27 / 6 1250 27 / 6 1355
Amber 28 / 6 1245 28 / 6 1450


Table 1.3   Thunderstorm Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
9 / 6 0900 9 / 6 1230
9 / 6 1530 9 / 6 1930
10 / 6 0110 10 / 6 1430
13 / 6 0005 13 / 6 0730
13 / 6 1240 13 / 6 1410
14 / 6 0037 14 / 6 0515
14 / 6 1140 14 / 6 1245
14 / 6 1645 14 / 6 1745
16 / 6 0235 16 / 6 0630
22 / 6 0220 22 / 6 0335
22 / 6 1025 22 / 6 1200
23 / 6 0510 23 / 6 0815
23 / 6 1045 23 / 6 1245
23 / 6 1605 23 / 6 1915
24 / 6 0810 24 / 6 1215
25 / 6 1210 25 / 6 1400
26 / 6 0235 26 / 6 2030
27 / 6 0700 27 / 6 1500
27 / 6 2345 28 / 6 0100
28 / 6 1025 28 / 6 1620
29 / 6 1325 29 / 6 1530


Table 2   Figures and Departures from Normal - June 2010

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 29.2 degrees C 1.2 degrees below normal
Mean Air Temperature 27.1 degrees C 0.8 degree below normal
Mean Daily Minimum Air Temperature 25.4 degrees C 0.7 degree below normal
Mean Dew Point Temperature 24.4 degrees C 0.2 degree below normal
Mean Relative Humidity 85 % 3 % above normal
Mean Cloud Amount 81 % 5 % above normal
Total Rainfall 474.9 mm 86.8 mm above normal
Number of hours of Reduced VisibilityΔ 21 hours normal§
Total Bright Sunshine Duration 92.5 hours 65.8 hours below normal
Mean Daily Global Solar Radiation 12.94 Megajoule / square metre 2.37 Megajoule below normal
Total Evaporation 100.3 mm 28.7 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 2009

daily values of selected meteorological elements for HK for June 2010

Extract of Meteorological Observations in Hong Kong for June 2010