An unusually dry and extremely hot July

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     With long spells of sunny skies under the dominance of the subtropical ridge, the weather was unusually hot in July 2016. The monthly mean temperature of 29.8 degrees was 1.0 degree higher than the normal figure of 28.8 degrees, equalling the previous highest record for July set in 2014. The month was much drier than usual with only 175.9 millimetres of rainfall, less than about half of the normal figure of 376.5 millimetres. The accumulated rainfall of 1408.7 millimetres for the first seven months is about 4 per cent below the normal figure of 1473.3 millimetres for the same period.

     Under the influence of an active southerly airstream, the weather in Hong Kong was hot with a mixture of sunshine, showers and thunderstorms on the first five days of the month. The setting in of an easterly airstream along the coastal areas of Guangdong gave rise to a relatively cool day on July 6 as rainbands from the northern part of the South China Sea brought heavy showers and squally thunderstorms to Hong Kong. More than 30 millimetres of rainfall fell over the territory and the lowest temperature of the month, 24.7 degrees, was recorded at the Hong Kong Observatory that morning.

     Over the western North Pacific, Super Typhoon Nepartak headed towards Taiwan on July 7 and made landfall at Fujian two days later. Affected by the subsiding air outside the circulation of Nepartak, local weather was sunny and very hot on July 7 to 9. The oppressive heat was most keenly felt on July 9 with temperatures at the Hong Kong Observatory soaring to a maximum of 35.6 degrees, the highest of the month and the second highest on record for July. Intense convection developed over inland Guangdong on the afternoon of July 9 and moved towards Hong Kong in the evening, bringing squally thunderstorms with incessant lightning and thunder that lasted throughout the night. Local weather remained mostly cloudy and unsettled with occasional heavy showers and thunderstorms over the next five days.

     With an upper-air anticyclone becoming established over southeastern China and the northern part of the South China Sea, a spell of generally fine weather with rather hot conditions set in on July 15 and persisted for more than two weeks. Despite a showery interlude on July 19 and 20, there were still long hours of sunshine and temperatures at the Hong Kong Observatory reached 35 degrees on July 25 as a tropical depression brewed over the central part of the South China Sea. It intensified into a tropical storm named Mirinae the next morning and its outer rainbands brought squally showers and thunderstorms to Hong Kong in the daytime. With Mirinae moving away from Hong Kong towards Hainan Island and northern Vietnam, fine and very hot weather prevailed in Hong Kong towards the end of the month. The high temperature on the afternoon of July 30 also triggered intense thunderstorm development over the New Territories. Hail was reported at Tai Po during the passage of the thunderstorms.

     Four tropical cyclones occurred over the South China Sea and the western North Pacific in the month.

     Details of the issuance and cancellation of various warnings/signals in the month are summarised in Table 1. Monthly meteorological figures and departures from normal for July are tabulated in Table 2.

Ends/Tuesday, August 2, 2016
Issued at HKT 15:00

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Table 1 (Warnings and Signals issued in July 2016)

Table 2 (Figures and Departures from Normal - July 2016)