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  • The Weather of June 2018

  • 4 July 2018

    After a very dry May, the long awaited rainfall eventually returned to Hong Kong in June 2018, mainly due to the passage of tropical cyclone Ewiniar in early June, as well as showery activities associated with troughs and an active southerly airstream later in the month. The monthly rainfall was 458.8 millimetres, slightly above the normal of 456.1 millimetres in June. However, with well below normal rainfall in the first five months, the accumulated rainfall recorded in the first half of the year was 633.8 millimetres, a deficit of 42 percent compared to the normal of 1096.9 millimetres for the same period. The month was also warmer than usual with a mean temperature of 28.6 degrees, 0.7 degree above the normal of 27.9 degrees.

    The heat wave in the latter half of May extended into early June. With plenty of sunshine in the morning, the temperature at the Hong Kong Observatory soared to the month’s highest of 35.1 degrees around noon on 1 June. The heat also triggered some isolated heavy showers and thunderstorms near Tai Po. An easterly airstream then reached the coastal area of Guangdong later in the day and the intense heat was slightly relieved by the windy conditions over the next couple of days.

    Meanwhile, an area of low pressure over the South China Sea intensified into a tropical depression on 2 June and was later named Ewiniar. It skirted past the east coast of Hainan Island and then turned in the general direction of the coastal areas of western Guangdong. The weather in Hong Kong became cloudy with some squally showers and thunderstorms on 4 June and tropical cyclone warning signal was issued for the first time this year on the morning of 5 June. After making landfall near Yangjiang on the night of 7 June, a weakening Ewiniar continued to drift towards the Pearl River Delta. Its rainbands brought heavy squally showers and thunderstorms to Hong Kong with more than 170 millimetres of rainfall generally recorded over the territory on 6 - 8 June. The heavy downpour necessitated the issuance of the first rainstorm warnings this year, including the Red Rainstorm Warning on 8 June. A waterspout was also spotted near Cheung Chau in the evening on 7 June. Local winds gradually subsided and the showers eased off on 9 June as generally fine weather returned.

    After a couple of fine and very hot days on 10 and 11 June, a trough of low pressure brought heavy showers and thunderstorms to the coast of Guangdong on 12 - 13 June. There was a report of waterspout near Ninepin Islands on the morning of 12 June, and more than 100 millimetres of rain fell over Sai Kung, Hong Kong Island and Cheung Chau on 13 June. The trough passed to the south of Hong Kong and local weather improved with a mixture of sunshine and isolated showers on 14 - 15 June. Despite the development of a low pressure area along the trough over the northern part of the South China Sea, the weather in Hong Kong remained mostly fine but windy on 16 – 17 June.

    Under the influence of the southwest monsoon, local weather was a mixture of sunny periods and showers on 18 - 21 June. An active southerly airstream brought more clouds and some heavy showers to the territory on 22 – 23 June. Another waterspout was observed near Cheung Chau on the morning of 22 June, and the temperature at the Hong Kong Observatory fell to the month’s lowest of 24.4 degrees on 23 June during heavy showers. Despite a sunny day on 24 June, more showers affected the territory that night and the next day.

    As the subtropical ridge became established over southeastern China, showery activities gradually decreased on 26 June. Under the influence of the southwest monsoon and despite still some showers around at times, the weather in Hong Kong remained mostly fine and hot till the end of the month.


A waterspout observed near 

Cheung Chau on the evening of 7 June 2018
A waterspout observed near Cheung Chau on the evening of 7 June 2018



A waterspout reported near 

Cheung Chau on the morning of 22 June 2018
A waterspout reported near Cheung Chau on the morning of 22 June 2018


     Four 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 1.6.  Monthly meteorological figures and departures from normal for June are tabulated in Table 2.
 

Warnings and Signals issued in June 2018

Table 1.1   Tropical Cyclone Warning Signals
Name of
Tropical Cyclone
Signal
Number
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
EWINIAR 1 5 / 6 1120 7 / 6 1240
3 7 / 6 1240 8 / 6 1540
1 8 / 6 1540 8 / 6 1820


Table 1.2   Rainstorm Warning Signals
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 6 / 6 1310 6 / 6 1450
Amber 8 / 6 0650 8 / 6 1130
Red 8 / 6 1130 8 / 6 1230
Amber 8 / 6 1230 8 / 6 1415
Amber 13 / 6 0210 13 / 6 0545
Amber 13 / 6 1500 13 / 6 1815
Amber 22 / 6 1215 22 / 6 1615
Amber 23 / 6 1115 23 / 6 1340


Table 1.3   Landslip Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
7 / 6 0740 8 / 6 1550


Table 1.4   Thunderstorm Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 6 1300 1 / 6 1430
1 / 6 2115 1 / 6 2230
1 / 6 2335 2 / 6 0045
4 / 6 1100 4 / 6 1230
4 / 6 1745 4 / 6 1900
5 / 6 0000 5 / 6 0500
5 / 6 0530 5 / 6 0700
5 / 6 1220 5 / 6 1630
5 / 6 1930 5 / 6 2130
6 / 6 0155 6 / 6 1800
6 / 6 2200 8 / 6 1500
9 / 6 0110 9 / 6 0600
12 / 6 0745 12 / 6 1600
13 / 6 0135 13 / 6 0600
13 / 6 0705 13 / 6 0830
13 / 6 1050 13 / 6 1200
13 / 6 1310 13 / 6 1930
19 / 6 1315 19 / 6 1600
20 / 6 1800 20 / 6 1830
21 / 6 0905 21 / 6 1000
21 / 6 1025 21 / 6 1130
21 / 6 1225 21 / 6 1330
21 / 6 1615 21 / 6 1935
22 / 6 0455 22 / 6 0630
22 / 6 1040 22 / 6 1800
23 / 6 0200 23 / 6 0400
23 / 6 0720 23 / 6 1645
24 / 6 2045 25 / 6 0130
25 / 6 0205 25 / 6 0430
25 / 6 0720 25 / 6 1400
25 / 6 1445 25 / 6 1630
25 / 6 2210 26 / 6 0045
26 / 6 0245 26 / 6 0600
27 / 6 1305 27 / 6 1515
30 / 6 1325 30 / 6 1430
30 / 6 1624 30 / 6 1700


Table 1.5   Very Hot Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
18 / 5 0645 1 / 6 1845
10 / 6 0645 11 / 6 1845
20 / 6 1200 21 / 6 1620
26 / 6 1440 27 / 6 1410
28 / 6 0645 1 / 7 1620


Table 1.6   Special Announcement on Flooding
in the Northern New Territories
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
6 / 6 1315 6 / 6 1800
7 / 6 0650 7 / 6 1105


Table 2   Figures and Departures from Normal - June 2018
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 28.6 degrees C 0.7 degree above normal
Mean Daily Minimum Air Temperature 26.8 degrees C 0.6 degree above normal
Mean Dew Point Temperature 24.7 degrees C 0.1 degree above normal
Mean Relative Humidity 80 % 2 % below normal
Mean Cloud Amount 79 % 2 % above normal
Total Rainfall 458.8 mm 2.7 mm above normal
Number of hours of Reduced VisibilityΔ 1 hour 15.8 hours below normal§
Total Bright Sunshine Duration 145.2 hours 0.9 hour below normal
Mean Daily Global Solar Radiation 15.17 Megajoule / square metre 0.98 Megajoule above normal
Total Evaporation 122.7 mm 5.6 mm above 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 2017

daily values of selected meteorological 

elements for HK for June 2018

The percentile map of mean temperature of June 2018

  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 2018