The Weather of August 2020
2 September 2020
Mainly attributing to the warmer than normal sea surface temperature over the northern part of the South China Sea, August 2020 was hotter than usual in Hong Kong. The monthly mean temperature of 29.0 degrees was 0.4 degree above the normal figure of 28.6 degrees. Together with the extremely high temperature weather in June and July, Hong Kong experienced the hottest summer on record from June to August 2020. The mean temperature of 29.6 degrees, mean minimum temperature of 27.7 degrees and mean maximum temperature of 32.6 degrees for June to August 2020 were all the highest on record for the same period. There were 16 very hot days in August 2020, the highest number of very hot days on record for August. Moreover, from January to August, the annual number of very hot days in 2020 already reached 43, which is 32.8 days above the annual normal and broke the previous highest record of 38 days set in 2016. The number of hot nights up to August 2020 also reached 46, on par with the highest record in 2019. The monthly rainfall was 448.4 millimetres, about 4 percent above the normal figure of 432.2 millimetres. The accumulated rainfall recorded in the first eight months of the year was 1537.2 millimetres, about 19 percent below the normal figure of 1905.5 millimetres for the same period.
Tropical depression Sinlaku over the northern part of the South China Sea moved generally west-northwestward and skirted past the southern coast of Hainan Island on 1 August. Sinlaku made landfall over the northern part of Vietnam and weakened gradually into an area of low pressure over inland the next day. Affected by Sinlaku, it was windy in Hong Kong on 1 August. The outer rainbands of Sinlaku also brought occasional heavy squally showers to the territory on 1-2 August. More than 50 millimetres of rainfall were generally recorded over Hong Kong on these two days and rainfall even exceeded 90 millimetres in the northern part of the New Territories.
Under the influence of a broad trough of low pressure, local weather remained unsettled with occasional heavy showers on 3 August. More than 30 millimetres of rainfall were recorded over Kowloon and the eastern part of Hong Kong Island and rainfall even exceeded 70 millimetres over Tuen Mun. With the weakening of the broad trough of low pressure, there were less showers with sunny intervals on 4 August. An active southerly airstream brought more showers and thunderstorms to Hong Kong again on 5 August. Showers were heavy in the morning and at night. More than 50 millimetres of rainfall were recorded over most parts of the territory and rainfall even exceeded 100 millimetres over Tai Po and Sha Tin on that day. Under the rain, the temperature at the Observatory dropped to a minimum of 24.9 degrees on the night of 5 August, the lowest of the month.
With the establishment of the subtropical ridge and the subsequent anticyclone aloft, the weather of Hong Kong became generally fine and very hot apart from a few showers on 6 – 10 August. With plenty of sunshine, the maximum temperature at the Observatory soared to 34.4 degrees on 8 August, the highest of the month. With the setting in of a southerly airstream, showers became more frequent with a few thunderstorms on 11 – 13 August. The showers were heavier on 12 August with more than 20 millimetres of rainfall over most parts of the territory.
Under the influence of an anticyclone aloft, apart from a few showers and isolated thunderstorms, it was generally fine and very hot in Hong Kong on 14 – 16 August. The high temperature also triggered isolated heavy thundery showers over the western part of the New Territories on 16 August. Local weather was a mixture of sunshine and a few showers and thunderstorms on 17 August.
Meanwhile, an area of low pressure gradually developed into a tropical depression over the northeastern part of the South China Sea in the small hours of 18 August and later named as Higos. It moved generally northwestward across the northern part of the South China Sea during the day and intensified rapidly on its course towards the coast of Guangdong. Higos made landfall over Zhuhai of Guangdong with typhoon strength in the early morning of 19 August and weakened gradually into an area of low pressure over inland that night.
The strike of Higos necessitated the issuance of the Gale or Storm Signal No. 8 on the night of 18 August and the Increasing Gale or Storm Signal No. 9 in the small hours of 19 August. Locally, winds strengthened on 18 August and increased significantly that night and in early morning on 19 August, reaching storm force offshore and hurricane force on high ground. Heavy squally showers and thunderstorms associated with the rainbands of Higos also brought more than 100 millimetres of rainfall to most parts of the territory and rainfall even exceeded 200 millimetres over parts of Hong Kong Island in these two days. In the midst of downpour, the temperature at the Observatory dropped to the month’s lowest of 24.9 degrees again on the morning of 19 August.
Affected by an anticyclone aloft, apart from isolated showers, the weather of Hong Kong turned generally fine and very hot on 20 – 25 August. Under the influence of an upper-air disturbance, local weather became cloudier with more showers and thunderstorms on the latter part of 26 August and 27 August. With the departure of the upper-air disturbance and affecting by a continental airstream, apart from isolated showers, the weather turned generally fine and very hot again towards the end of the month.
Eight tropical cyclones occurred over the South China Sea and the western North Pacific in August 2020.
Mainly attributing to the warmer than normal sea surface temperature over the northern part of the South China Sea, August 2020 was hotter than usual in Hong Kong. The monthly mean temperature of 29.0 degrees was 0.4 degree above the normal figure of 28.6 degrees. Together with the extremely high temperature weather in June and July, Hong Kong experienced the hottest summer on record from June to August 2020. The mean temperature of 29.6 degrees, mean minimum temperature of 27.7 degrees and mean maximum temperature of 32.6 degrees for June to August 2020 were all the highest on record for the same period. There were 16 very hot days in August 2020, the highest number of very hot days on record for August. Moreover, from January to August, the annual number of very hot days in 2020 already reached 43, which is 32.8 days above the annual normal and broke the previous highest record of 38 days set in 2016. The number of hot nights up to August 2020 also reached 46, on par with the highest record in 2019. The monthly rainfall was 448.4 millimetres, about 4 percent above the normal figure of 432.2 millimetres. The accumulated rainfall recorded in the first eight months of the year was 1537.2 millimetres, about 19 percent below the normal figure of 1905.5 millimetres for the same period.
Tropical depression Sinlaku over the northern part of the South China Sea moved generally west-northwestward and skirted past the southern coast of Hainan Island on 1 August. Sinlaku made landfall over the northern part of Vietnam and weakened gradually into an area of low pressure over inland the next day. Affected by Sinlaku, it was windy in Hong Kong on 1 August. The outer rainbands of Sinlaku also brought occasional heavy squally showers to the territory on 1-2 August. More than 50 millimetres of rainfall were generally recorded over Hong Kong on these two days and rainfall even exceeded 90 millimetres in the northern part of the New Territories.
Under the influence of a broad trough of low pressure, local weather remained unsettled with occasional heavy showers on 3 August. More than 30 millimetres of rainfall were recorded over Kowloon and the eastern part of Hong Kong Island and rainfall even exceeded 70 millimetres over Tuen Mun. With the weakening of the broad trough of low pressure, there were less showers with sunny intervals on 4 August. An active southerly airstream brought more showers and thunderstorms to Hong Kong again on 5 August. Showers were heavy in the morning and at night. More than 50 millimetres of rainfall were recorded over most parts of the territory and rainfall even exceeded 100 millimetres over Tai Po and Sha Tin on that day. Under the rain, the temperature at the Observatory dropped to a minimum of 24.9 degrees on the night of 5 August, the lowest of the month.
With the establishment of the subtropical ridge and the subsequent anticyclone aloft, the weather of Hong Kong became generally fine and very hot apart from a few showers on 6 – 10 August. With plenty of sunshine, the maximum temperature at the Observatory soared to 34.4 degrees on 8 August, the highest of the month. With the setting in of a southerly airstream, showers became more frequent with a few thunderstorms on 11 – 13 August. The showers were heavier on 12 August with more than 20 millimetres of rainfall over most parts of the territory.
Under the influence of an anticyclone aloft, apart from a few showers and isolated thunderstorms, it was generally fine and very hot in Hong Kong on 14 – 16 August. The high temperature also triggered isolated heavy thundery showers over the western part of the New Territories on 16 August. Local weather was a mixture of sunshine and a few showers and thunderstorms on 17 August.
Meanwhile, an area of low pressure gradually developed into a tropical depression over the northeastern part of the South China Sea in the small hours of 18 August and later named as Higos. It moved generally northwestward across the northern part of the South China Sea during the day and intensified rapidly on its course towards the coast of Guangdong. Higos made landfall over Zhuhai of Guangdong with typhoon strength in the early morning of 19 August and weakened gradually into an area of low pressure over inland that night.
The strike of Higos necessitated the issuance of the Gale or Storm Signal No. 8 on the night of 18 August and the Increasing Gale or Storm Signal No. 9 in the small hours of 19 August. Locally, winds strengthened on 18 August and increased significantly that night and in early morning on 19 August, reaching storm force offshore and hurricane force on high ground. Heavy squally showers and thunderstorms associated with the rainbands of Higos also brought more than 100 millimetres of rainfall to most parts of the territory and rainfall even exceeded 200 millimetres over parts of Hong Kong Island in these two days. In the midst of downpour, the temperature at the Observatory dropped to the month’s lowest of 24.9 degrees again on the morning of 19 August.
Affected by an anticyclone aloft, apart from isolated showers, the weather of Hong Kong turned generally fine and very hot on 20 – 25 August. Under the influence of an upper-air disturbance, local weather became cloudier with more showers and thunderstorms on the latter part of 26 August and 27 August. With the departure of the upper-air disturbance and affecting by a continental airstream, apart from isolated showers, the weather turned generally fine and very hot again towards the end of the month.
Eight tropical cyclones occurred over the South China Sea and the western North Pacific in August 2020.
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 August are tabulated in Table 2.
Warnings and Signals issued in August 2020
| Name of Tropical Cyclone |
Signal Number |
Beginning Time | Ending Time | ||
|---|---|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT | ||
| SINLAKU | 3 | 31 / 7 | 2040 | 1 / 8 | 2110 |
| 1 | 1 / 8 | 2110 | 1 / 8 | 2315 | |
| HIGOS | 1 | 18 / 8 | 0340 | 18 / 8 | 1420 |
| 3 | 18 / 8 | 1420 | 18 / 8 | 2240 | |
| 8 NE | 18 / 8 | 2240 | 19 / 8 | 0130 | |
| 9 | 19 / 8 | 0130 | 19 / 8 | 0740 | |
| 8 SE | 19 / 8 | 0740 | 19 / 8 | 1110 | |
| 3 | 19 / 8 | 1110 | 19 / 8 | 1320 | |
| Colour | Beginning Time | Ending Time | ||
|---|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT | |
| Amber | 5 / 8 | 1955 | 6 / 8 | 0040 |
| Amber | 18 / 8 | 2320 | 19 / 8 | 1050 |
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 19 / 8 | 0545 | 19 / 8 | 1545 |
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 31 / 7 | 2150 | 1 / 8 | 0915 |
| 2 / 8 | 0400 | 2 / 8 | 0830 |
| 3 / 8 | 1300 | 3 / 8 | 1430 |
| 4 / 8 | 1220 | 4 / 8 | 1430 |
| 4 / 8 | 2100 | 4 / 8 | 2230 |
| 5 / 8 | 0535 | 5 / 8 | 0645 |
| 5 / 8 | 0955 | 5 / 8 | 1300 |
| 5 / 8 | 1510 | 6 / 8 | 0040 |
| 7 / 8 | 0505 | 7 / 8 | 0545 |
| 11 / 8 | 0750 | 11 / 8 | 0900 |
| 11 / 8 | 1007 | 11 / 8 | 1330 |
| 11 / 8 | 2040 | 12 / 8 | 1615 |
| 12 / 8 | 2000 | 12 / 8 | 2230 |
| 13 / 8 | 0005 | 13 / 8 | 0500 |
| 13 / 8 | 1015 | 13 / 8 | 1500 |
| 15 / 8 | 1225 | 15 / 8 | 1630 |
| 16 / 8 | 0405 | 16 / 8 | 0730 |
| 16 / 8 | 1335 | 16 / 8 | 1615 |
| 17 / 8 | 0425 | 17 / 8 | 1700 |
| 18 / 8 | 0955 | 19 / 8 | 0100 |
| 19 / 8 | 0230 | 19 / 8 | 1500 |
| 20 / 8 | 1250 | 20 / 8 | 1445 |
| 21 / 8 | 1617 | 21 / 8 | 1800 |
| 22 / 8 | 1425 | 22 / 8 | 1700 |
| 26 / 8 | 0400 | 26 / 8 | 0500 |
| 26 / 8 | 1215 | 26 / 8 | 1600 |
| 26 / 8 | 1955 | 27 / 8 | 0500 |
| 27 / 8 | 1350 | 27 / 8 | 1800 |
| 28 / 8 | 1455 | 28 / 8 | 1615 |
| 29 / 8 | 1250 | 29 / 8 | 1430 |
| 31 / 8 | 1205 | 31 / 8 | 1700 |
| 31 / 8 | 2115 | 1 / 9 | 0200 |
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 6 / 8 | 1240 | 11 / 8 | 1620 |
| 14 / 8 | 0915 | 15 / 8 | 1730 |
| 16 / 8 | 1115 | 16 / 8 | 1800 |
| 21 / 8 | 0645 | 24 / 8 | 1800 |
| 25 / 8 | 0900 | 25 / 8 | 1830 |
| 26 / 8 | 1050 | 26 / 8 | 1615 |
| 28 / 8 | 0645 | 4 / 9 | 1620 |
| Meteorological Element | Figure of the Month | Departure from Normal* |
|---|---|---|
| Mean Daily Maximum Air Temperature | 32.2 degrees C | 1.1 degrees above normal |
| Mean Air Temperature | 29.0 degrees C | 0.4 degree above normal |
| Mean Daily Minimum Air Temperature | 26.9 degrees C | 0.3 degree above normal |
| Mean Dew Point Temperature | 25.4 degrees C | 0.4 degree above normal |
| Mean Relative Humidity | 82 % | 1 % above normal |
| Mean Cloud Amount | 73 % | 4 % above normal |
| Total Rainfall | 448.4 mm | 16.2 mm above normal |
| Number of hours of Reduced VisibilityΔ | 0 hour | 44.4 hours below normal§ |
| Total Bright Sunshine Duration | 195.7 hours | 6.8 hours above normal |
| Mean Daily Global Solar Radiation | 17.54 Megajoule / square metre | 1.91 Megajoule above normal |
| Total Evaporation | 110.6 mm | 24.3 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. |
* Departure from 1981 - 2010 climatological normal, except for number of hours of reduced visibility |
|
§ Departure from mean value between 1997 and 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 |
