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  • The Weather of June 2017

  • 4 July 2017

    As a result of the very hot weather in early June and the rainy spell in mid-June, the month was overall warmer and wetter than usual. The monthly mean temperature was 28.8 degrees, 0.9 degree above the normal of 27.9 degrees. The total rainfall recorded in the month was 656.0 millimetres, about 44 percent above the June normal of 456.1 millimetres. The accumulated rainfall recorded in the first half year was 1189.8 millimetres, a surplus of 8 percent compared to the normal of 1096.9 millimetres for the same period.

    Under the influence of an active southwest monsoon, the weather was mainly cloudy and showery on the first two days of the month. The weather turned brighter on 3 June, and with winds subsiding and more sunshine, the weather became very hot on 5 – 7 June. Despite the fine conditions, a lingering trough over the inland areas of Guangdong also led to some significant development of showery activities along the coast that affected the territory on 6 and 7 June. Generally fine weather persisted till 11 June with temperature at the Hong Kong Observatory that day soaring to a maximum of 34.1 degrees, the highest of the month.

    Meanwhile, an area of low pressure over the South China Sea developed into a tropical storm, named Merbok, on 11 June. Merbok moved across the northern part of the South China Sea on 12 June and intensified further into a severe tropical storm that night. It traversed the eastern part of Hong Kong waters and made landfall over the Dapeng Peninsula before midnight. With the approach of Merbok, local winds strengthened significantly with heavy squally showers later on 12 June, leading to the issuance of the No.8 Gale or Storm Signal for the first time in June since 2012. As Merbok weakened over land, its rainbands continued to affect the south China coastal region with gusty winds and heavy rain, with temperature at the Hong Kong Observatory falling to the month’s lowest of 24.3 degrees in rain and the issuance of the Red Rainstorm Warning Signal on the morning of 13 June. More than 150 millimetres of rainfall were generally recorded over the territory on 13 – 14 June, with rainfall over the urban areas exceeding 250 millimetres.

    Under the influence of an enhanced southwest monsoon in the wake of Merbok on 15 and 16 June and with the development of a lingering trough of low pressure along the coastal areas of the Guangdong, the weather remained unstable and rainy till 21 June. In particular, outbreaks of heavy rain and squally thunderstorms on 17 June brought more than 100 millimetres of rainfall to the territory and again led to the issuance of the Red Rainstorm Warning Signal.

    After the dissipation of the trough, the weather turned fine and hot on 22 June. A mixture of sunshine and showers then persisted for the next five days. Despite the development of another trough over southern China, showery activities over the coastal region gradually subsided and daytime conditions became very hot as generally fine weather prevailed over the territory towards the end of the month.


A retaining wall at Tai Tam Road in Stanley collapsed under the heavy rain on 13 June (courtesy of the Geotechnical Engineering Office and the Civil Engineering and Development Department)
A retaining wall at Tai Tam Road in Stanley collapsed under the heavy rain on 13 June
(courtesy of the Geotechnical Engineering Office and the Civil Engineering and Development Department)


    One tropical cyclone occurred 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 1.7.  Monthly meteorological figures and departures from normal for June are tabulated in Table 2.
 

Warnings and Signals issued in June 2017

Table 1.1   Tropical Cyclone Warning Signals
Name of
Tropical Cyclone
Signal
Number
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
MERBOK 1 11 / 6 1940 12 / 6 1040
3 12 / 6 1040 12 / 6 1720
8 NE 12 / 6 1720 12 / 6 2020
8 NW 12 / 6 2020 13 / 6 0010
8 SW 13 / 6 0010 13 / 6 0440
3 13 / 6 0440 13 / 6 1110


Table 1.2   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
2 / 6 1020 2 / 6 1840


Table 1.3   Rainstorm Warning Signals
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 13 / 6 0250 13 / 6 0845
Red 13 / 6 0845 13 / 6 1150
Amber 13 / 6 1150 13 / 6 1230
Amber 17 / 6 0150 17 / 6 0225
Red 17 / 6 0225 17 / 6 0405
Amber 17 / 6 2040 17 / 6 2215
Amber 21 / 6 0120 21 / 6 0245


Table 1.4   Landslip Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
13 / 6 0855 13 / 6 2100


Table 1.5   Thunderstorm Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
6 / 6 0525 6 / 6 0630
6 / 6 0915 6 / 6 1015
7 / 6 0420 7 / 6 0630
9 / 6 0810 9 / 6 0915
12 / 6 2310 13 / 6 1630
13 / 6 2225 14 / 6 0030
14 / 6 0755 14 / 6 0930
15 / 6 0635 15 / 6 0830
15 / 6 1030 15 / 6 1300
15 / 6 1345 15 / 6 1500
16 / 6 0005 16 / 6 1430
16 / 6 2205 17 / 6 0630
17 / 6 1235 17 / 6 1645
17 / 6 2000 17 / 6 2330
18 / 6 0840 18 / 6 1445
18 / 6 1930 18 / 6 2130
19 / 6 0530 19 / 6 1100
19 / 6 1540 19 / 6 1800
20 / 6 0900 20 / 6 1030
20 / 6 1150 20 / 6 1430
20 / 6 2000 20 / 6 2055
20 / 6 2215 21 / 6 1430
21 / 6 1645 21 / 6 1945
23 / 6 1330 23 / 6 1430
24 / 6 1145 24 / 6 1415
26 / 6 1300 26 / 6 1400
27 / 6 1240 27 / 6 1345
30 / 6 1020 30 / 6 1130


Table 1.6   Very Hot Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
3 / 6 1255 3 / 6 1800
5 / 6 1210 12 / 6 0505
23 / 6 0945 23 / 6 1620
27 / 6 0730 27 / 6 1715
30 / 6 1145 30 / 6 1830


Table 1.7   Special Announcement on Flooding
in the Northern New Territories
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
13 / 6 0935 13 / 6 1510


Table 2   Figures and Departures from Normal - June 2017
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 31.3 degrees C 1.1 degrees above normal
Mean Air Temperature 28.8 degrees C 0.9 degree above normal
Mean Daily Minimum Air Temperature 27.2 degrees C 1.0 degree above normal
Mean Dew Point Temperature 25.6 degrees C 1.0 degree above normal
Mean Relative Humidity 83 % 1 % above normal
Mean Cloud Amount 78 % 1 % above normal
Total Rainfall 656.0 mm 199.9 mm above normal
Number of hours of Reduced VisibilityΔ 0 hour 17.6 hours below normal§
Total Bright Sunshine Duration 138.9 hours 7.2 hours below normal
Mean Daily Global Solar Radiation 15.42 Megajoule / square metre 1.23 Megajoule above normal
Total Evaporation 101.4 mm 15.7 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 1981 - 2010 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2016

daily values of selected meteorological elements for HK for June 2017

The percentile map of mean temperature of June 2017

  Remarks : Extremely high: above 95th percentile
Above normal: between 75th and 95th percentile
Normal: between 25th and 75th percentile
Below normal: between 5th and 25th percentile
Extremely low: below 5th percentile
Percentile and 5-day running average values are
computed based on the data from 1981 to 2010


Extract of Meteorological Observations in Hong Kong for June 2017