The Weather of October 2013

    With the dominance of dry northeast monsoon for most of the time in the month, October 2013 was sunnier and drier than usual.  The monthly total duration of bright sunshine was 247.3 hours, about 28 percent above the normal figure of 193.9 hours.  The monthly mean relative humidity of 66 percent was the third lowest for October since 1961.  Also, the monthly total rainfall was 2.9 millimetres, only about 3 percent of the normal figure of 100.9 millimetres.  However, the accumulated rainfall since 1 January of 2675.9 millimetres was still about 15 percent above the normal figure of 2334.0 millimetres for the same period.  The month was also slightly warmer than usual. The monthly mean temperature of 25.7 degrees was 0.2 degrees above the normal figure of 25.5 degrees.  

    Under the influence of a dry northeast monsoon, the weather in Hong Kong was fine and dry for the first seven days of October 2013.  With abundant sunshine, temperatures at the Hong Kong Observatory rose to a maximum of 32.0 degrees on 7 October, the highest of the month.  As a cloud band moved over southern China, the weather in Hong Kong turned cloudy with a few rain patches on 8 October.  Clouds dissipated gradually on 9 October and, apart from some nocturnal rain, the weather was mainly fine in the next three days. 

    Meanwhile, Typhoon Nari moved across Luzon and entered the South China Sea on 12 October.  Nari tracked generally westwards over the next two days and made landfall in central Vietnam on the morning of 15 October.  Under the combined effect of Nari and a fresh to strong northeast monsoon over the coast of Guangdong, it was windy in Hong Kong on 13 and 14 October.  The outer rainbands of Nari also brought mainly cloudy weather and a few rain patches on 14 October and the next morning.  

    A cold front from inland Guangdong edged southwards on 15 October and moved across the coastal areas the next morning.  Affected by the cold front, the weather in Hong Kong became cloudy and windy with light rain patches on 16 and 17 October.  With clouds thinning out, local weather became fine and dry on 18 October.  Dominated by a dry continental airstream, daytime relative humidity fell to 40 percent or below from 23 to 26 October.  Meanwhile, a replenishment of the northeast monsoon reached the south China coast on the morning of 26 October, bringing cooler weather to Hong Kong.  Temperatures at the Hong Kong Observatory fell to a minimum of 19.4 degrees that morning, the lowest of the month.  Under the influence of the northeast monsoon, the weather remained generally fine till the end of the month.