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August 2015 was hotter and drier than usual. The mean temperature in the month was 29.3 degrees, 0.7 degree above the normal figure of 28.6 degrees and the seventh highest for August on record. The monthly total rainfall recorded in August 2015 was 143.3 millimetres, only about one-third of the normal figure of 432.2 millimetres. The accumulated rainfall of 1520.1 millimetres since January this year was about 20 per cent below the normal figure of 1905.5 millimetres for the same period.
With a ridge of high pressure strengthening and extending westward from the western North Pacific to southern China, August 2015 started with a spell of fine weather. With plenty of sunshine, conditions became very hot during the day with maximum temperatures exceeding 33 degrees from August 3 to 7. As Severe Typhoon Soudelor moved across Taiwan and made landfall over Fujian, the summer heat grew even more intense on August 8 to 9 under the subsidence effect ahead of Soudelor. With northwesterly winds bringing haze and a relatively dry air mass to Hong Kong, temperatures at the Observatory soared to a maximum of 36.3 degrees on the afternoon of August 8, an all-time high since records began in 1884.
While it remained mostly fine and very hot during the day on August 9, local weather also became more unsettled that night under the influence of a southwesterly airstream, with squally thunderstorms and showers bringing more than 30 millimetres of rain to many parts of the territory, especially over the New Territories. Apart from a generally fine and very hot day on August 12, showers and thunderstorms continued to affect Hong Kong on August 10 to 16. The red rainstorm warning was issued on August 15, with more than 100 millimetres of rain recorded over the New Territories.
The weather in Hong Kong turned fine on August 17 and it was mostly a mixture of sunshine and showers with some very hot days in the week that followed. With another typhoon, Goni, east of Taiwan tracking towards Japan and causing an enhanced subsidence effect and off-land flow over the south China coastal areas, daytime temperatures in Hong Kong again reached 33 degrees and higher on August 24 to 25.
With a trough of low pressure developing and lingering over the coast of Guangdong, the weather turned cloudier and more showery towards the end of the month.
Four tropical cyclones 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 summarised in Table 1. Monthly meteorological figures and departures from normal for August are tabulated in Table 2.
Ends/Wednesday, September 2, 2015
Issued at HKT 17:44
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