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  • The Weather of June 2019

  • 3 July 2019

    Mainly attributing to the warmer than normal sea surface temperature and stronger than usual southerly flow in the lower atmosphere over the northern part of the South China Sea, June 2019 was much hotter than usual in Hong Kong. The monthly mean temperature of 29.0 degrees was 1.1 degree above the normal figure of 27.9 degrees, one of the third highest on record for June. Moreover, the first half of this year from January to June 2019 was exceptionally warm. The mean temperature of 23.0 degrees, mean minimum temperature of 21.3 degrees and mean maximum temperature of 25.4 degrees were all the highest on record for the same period. The monthly rainfall of June 2019 was 429.1 millimetres, about 6 percent below the normal of 456.1 millimetres. The accumulated rainfall recorded in the first six months of the year was 1109.4 millimetres, slightly higher than the normal figure of 1096.9 millimetres for the same period.

    Under the influence of a trough of low pressure and an upper-air disturbance, there were heavy showers and squally thunderstorms on the first day of June in Hong Kong. More than 30 millimetres of rainfall were recorded in many places, and rainfall even exceeded 70 millimetres over Sai Kung and Kwun Tong. The upper-air disturbance continued to bring thundery showers to the territory on the next three days. Heavy showers on the morning of 4 June brought more than 90 millimetres of rainfall to Sai Kung District and Eastern District.

    With the departure of the upper-air disturbance and strengthening of the anticyclone aloft over the northern part of South China Sea, the weather in Hong Kong turned generally fine and hot apart from isolated showers on 5 – 8 June. With plenty of sunshine, the maximum temperature at the Observatory soared to 33.2 degrees on 7 June, the third hottest Tuen Ng Festival on record. As the anticyclone aloft weakened, local weather became more showery on 9 and 10 June.

    Meanwhile, a trough of low pressure over the northern part of south China edged southwards gradually and lingered over the south China coastal areas on 11 – 13 June. Locally, the weather deteriorated again with occasional heavy downpour and squally thunderstorms. More than 160 millimetres of rainfall were recorded at the Observatory in these three days. Under the rain, the temperature at the Observatory dropped to a minimum of 24.6 degrees on 11 June, the lowest of the month. With the trough of low pressure moving away from the coastal areas, local weather turned generally fine during the day on 14 June. Affected by a dry easterly airstream over the coast of Guangdong, the weather in Hong Kong remained generally fine on the next two days. With the weakening of the easterly airstream, it was mainly cloudy with a few showers on 17 – 19 June.

    With the anticyclone aloft strengthening again over the south China coast, apart from isolated showers, local weather was fine and very hot during the day on 20 – 23 June. The daily minimum temperature of 29.5 degrees on 21 June was the highest on record for June and the daily mean temperature of 30.8 degrees on the same day was also the hottest Summer Solstice on record. Affected by the trough of low pressure over the south China coast, the weather in Hong Kong became unsettled with outbreaks of heavy showers and thunderstorms on 24 – 26 June. Heavy showers brought more than 80 millimetres of rainfall to Tseung Kwan O, Tai Po and parts of Hong Kong Island in these three days. With the weakening of the trough of low pressure and the prevailing of a southerly airstream, local weather became very hot with a mixture of sunshine and showers towards the end of the month. With plenty of sunshine during the day, the maximum temperature at the Observatory soared to 33.3 degrees on 29 June, the highest of the month. The daily minimum temperature of 29.5 degrees was also recorded on that day, on a par with that of 21 June as the highest on record for June.


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

Warnings and Signals issued in June 2019

Table 1.1   Rainstorm Warning Signals
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 1 / 6 0250 1 / 6 0405
Amber 4 / 6 0905 4 / 6 1005
Amber 11 / 6 0525 11 / 6 0740
Amber 13 / 6 0845 13 / 6 1000
Amber 13 / 6 1430 13 / 6 1720
Amber 14 / 6 0045 14 / 6 0145
Amber 25 / 6 1615 25 / 6 1755


Table 1.2   Thunderstorm Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 6 0045 1 / 6 0500
1 / 6 2105 1 / 6 2345
2 / 6 1350 2 / 6 1745
3 / 6 0340 3 / 6 0930
4 / 6 0335 4 / 6 1330
4 / 6 1420 4 / 6 1900
8 / 6 0700 8 / 6 0730
8 / 6 0845 8 / 6 0915
9 / 6 0200 9 / 6 0330
9 / 6 1020 9 / 6 1230
10 / 6 0745 10 / 6 0855
10 / 6 1130 10 / 6 1300
10 / 6 1720 10 / 6 2000
11 / 6 0122 11 / 6 0805
11 / 6 0925 11 / 6 1400
11 / 6 1630 11 / 6 2035
12 / 6 1205 12 / 6 1430
12 / 6 1510 12 / 6 2000
13 / 6 0010 13 / 6 0630
13 / 6 0730 13 / 6 1130
13 / 6 1400 13 / 6 1900
13 / 6 2325 14 / 6 0330
17 / 6 1155 17 / 6 1300
18 / 6 0855 18 / 6 1015
18 / 6 1215 18 / 6 1515
24 / 6 0330 24 / 6 0830
24 / 6 0945 24 / 6 1945
24 / 6 2140 25 / 6 0015
25 / 6 1305 25 / 6 2030
26 / 6 0030 26 / 6 0140
26 / 6 0525 26 / 6 0700
28 / 6 1255 28 / 6 1500
29 / 6 0840 29 / 6 1200
30 / 6 0240 30 / 6 0700
30 / 6 1401 30 / 6 1800


Table 1.3   Very Hot Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
5 / 6 1305 5 / 6 1620
6 / 6 0645 8 / 6 1800
20 / 6 0745 23 / 6 1620
27 / 6 1055 27 / 6 1800
28 / 6 0945 29 / 6 1830


Table 2   Figures and Departures from Normal - June 2019
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 31.5 degrees C 1.3 degrees above normal
Mean Air Temperature 29.0 degrees C 1.1 degrees above normal
Mean Daily Minimum Air Temperature 27.0 degrees C 0.8 degree above normal
Mean Dew Point Temperature 25.7 degrees C 1.1 degrees above normal
Mean Relative Humidity 83 % 1 % above normal
Mean Cloud Amount 79 % 2 % above normal
Total Rainfall 429.1 mm 27.0 mm below normal
Number of hours of Reduced VisibilityΔ 2 hours 14.0 hours below normal§
Total Bright Sunshine Duration 153.9 hours 7.8 hours above normal
Mean Daily Global Solar Radiation 16.32 Megajoule / square metre 2.13 Megajoule above normal
Total Evaporation 100.5 mm 16.6 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 2018

daily values of selected meteorological elements for HK for June 2019

The percentile map of mean temperature of June 2019

  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 2019