The Weather of October 2015

    The weather of October 2015 was warmer than usual. The monthly mean temperature of 26.0 degrees was 0.5 degrees above the normal figure of 25.5 degrees. The month was also wetter than usual, mainly as a result of heavy rain brought by tropical cyclone Mujigae during the first week of the month. A total of 168.3 millimetres of rainfall was recorded of the month, about 67 percent above the normal figure of 100.9 millimetres. However, the accumulated rainfall of 1787.4 millimetres since 1 January was still about 23 percent below the normal figure of 2334.0 millimetres for the same period.

    The weather in Hong Kong was cloudy with a few showers and isolated thunderstorms on the first day of the month. Under the influence of the northeast monsoon, there were sunny periods and a few showers the next day. Meanwhile, the tropical depression near the Philippines intensified into a tropical storm and named Mujigae while moving into the South China Sea on the morning of 2 October. Moving west-northwestwards steadily, it edged closer to western Guangdong and continued to intensify in the next two days. Mujigae developed into a severe typhoon in the small hours of 4 October.

    Locally, east to northeasterly winds strengthened significantly and the weather also deteriorated with heavy squally showers and isolated thunderstorms in the afternoon on 3 October. With Mujigae making landfall near Zhanjiang of Guangdong and weakening gradually on the afternoon of 4 October, local winds started to subside gradually. Under the influence of the outer rainbands of Mujigae, there were occasional heavy squally showers and thunderstorms in Hong Kong on 4 and 5 October. In particular, more than 40 millimeters of rainfall were recorded over most parts of the territory and rainfall over western part of Lantau Island even exceeded 100 millimeters on 4 October.

    Affected by the cloud bands associated with the northeast monsoon, it remained cloudy and showery on 6-7 October. There was also a localized heavy downpour in the eastern part of the New Territories with more than 150 millimetres of rain falling over Sai Kung on the morning of 7 October. Under the influence of a continental airstream, the clouds thinned out with sunny periods in Hong Kong on 8 and 9 October. With the strengthening of the northeast monsoon, it became windy with a few rain patches on 10 October. The weather became appreciably cooler on the morning of 11 October with temperatures at the Observatory falling to a minimum of 18.5 degrees, the lowest of the month. The weather remained cloudy on the next day.

    Dominated by a relatively dry northeast monsoon, the weather in Hong Kong became fine on 13 October and remained generally fine and dry for the ensuing eleven days. Affected by an easterly airstream, local weather turned mainly cloudy with a few light rain patches on 25 and 26 October. As the band of clouds covering the coast of Guangdong thinned out, weather remained generally fine on 27-30 October. A cold front moved across the coastal areas of Guangdong on the morning of 31 October and brought cloudier weather with a few rain patches to the territory.