The Weather of September 2016

    With rainy weather dominating the first part of the month, September 2016 was gloomier than usual. The total duration of sunshine recorded in the month was 135.7 hours, 36.6 hours below the normal figure of 172.3 hours and the seventh lowest on record for September. However, the month was slightly warmer than usual with a monthly mean temperature of 27.9 degrees, 0.2 degree higher than the normal figure of 27.7 degrees. The monthly total rainfall was 323.1 millimetres, slightly below the normal figure of 327.6 millimetres. The accumulated rainfall of 2264.5 millimetres for the first nine months was about 1 percent above the normal figure of 2233.1 millimetres for the same period.

    With a trough of low pressure lingering over the South China coast, the weather in Hong Kong was unstable with showers and thunderstorms on the first ten days of the month. The showers were particularly heavy on 1, 5 and 10 September with over 30 millimetres of rainfall generally over the territory. With the trough of low pressure weakening gradually, there were sunny periods and a few showers on 11 September.

    Under the dominance of the anticyclone over southern China, local weather became generally fine apart from a few isolated showers on 12-13 September. Meanwhile, Super Typhoon Meranti moved across the Luzon Strait on the night of 13 September and swept across the coastal waters of southwestern Taiwan the next day. Affected by the outer subsiding air associated with Meranti, the weather in Hong Kong was very hot and dry on 14 September with temperatures rising to about 33 degrees over most parts of the territory. With Meranti making landfall near Xiamen and weakening over inland, the cloud band associated with Meranti covered eastern Guangdong and there were a few isolated showers in Hong Kong on 15 September.

    Under the influence of a relatively dry continental airstream, it was mainly fine, hot and dry in Hong Kong on 16-18 September. While it remained generally fine during the day on 19 September, with the northeast monsoon setting in, local weather turned cloudy with some rain that night. Affected by the northeast monsoon, the weather became cooler and rainy on 20 September. With the gradual thinning of cloud covering the south China coastal areas, the weather became mainly fine on 21-26 September.

    Over the western North Pacific, Severe Typhoon Megi moved across Taiwan on the afternoon of 27 September and made landfall at Fujian the next morning. Megi moved westward across Fujian and weakened gradually on 28 September. It degenerated into an area of low pressure over Jiangxi on the morning of 29 September. Under the subsidence effect ahead of Megi, local weather was very hot and hazy on 27 September with temperatures at the Observatory reaching a maximum of 34.9 degrees, the highest of the month and the second highest on record for September. With Megi taking a more westerly track and edging closer to Guangdong, local winds strengthened from the northwest and cleared the haze on 28 September. Under the influence of the northeast monsoon, it was mainly cloudy and cooler for the rest of the month.