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July 2015 was warmer and cloudier than usual. The mean temperature in the month was 29.1 degrees, 0.3 degrees above the normal figure of 28.8 degrees. The monthly mean cloud amount of 75 per cent was 6 per cent above the normal figure of 69 per cent. With the increase in cloudiness, the total sunshine duration recorded in July 2015 was only 164.9 hours, about 22 per cent below normal. The month was also wetter than usual with a monthly total rainfall of 406.2 millimetres, 8 per cent above the normal figure of 376.5 millimetres. The accumulated rainfall of 1 376.8 millimetres since January was about 7 per cent below the normal figure of 1 473.3 millimetres for the same period.
The weather in Hong Kong was mainly fine and very hot for the first five days of the month. A weakening trough of low pressure from Guangdong approached the coastal areas, bringing clouds and a few showers to the territory on July 6. In the meantime, the slow-moving tropical cyclone Linfa hovered over the northeastern part of the South China Sea. Dominated by its circulation, a northerly airstream of continental origin brought mainly fine and relatively dry conditions to the coastal region on July 7 and 8.
Linfa intensified into a typhoon and made landfall over the coast of eastern Guangdong on July 9. Local winds strengthened gradually in the afternoon with occasional gales on high ground. Tracking generally westwards along the coastal strip of Guangdong, Linfa weakened rapidly during the night. After some morning rain on July 10, the weather rapidly improved during the day and a spell of very hot weather persisted over the following nine days. The maximum temperature at the Observatory reached 34.4 degrees on July 13, the highest for the month. The weather also became increasingly unsettled with less sunshine and more showers. The showers were thundery at times and heavy in places, particularly over the western part of the territory on July 17, when more than 200 millimetres of rainfall were recorded near Chek Lap Kok in Lantau Island.
With an area of low pressure lingering over the coast of Guangdong and the development of an embedded trough, the weather deteriorated further on July 20. Following the dissipation of the trough, rainbands and thunderstorms from the northern part of the South China Sea continued to affect the territory under the influence of a moist southerly airstream. The rain was especially heavy over the urban areas on July 22 and over the northern part of the New Territories on July 24. A waterspout was reported near Kau Yi Chau on the morning of July 22. Despite the rain easing off and some sunny periods emerging on July 27, showery conditions continued to affect Hong Kong until the weather turned fine on the last day of the month.
Five 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 July are tabulated in Table 2.
Ends/Tuesday, August 4, 2015
Issued at HKT 18:40
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