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The mean temperature for October 2010 was 24.8 degrees, 0.5 degrees below normal. This was attributed to an intense northeast monsoon over southern China during the last six days of the month. A minimum temperature of 15.7 degrees, recorded on October 28, was the lowest in October since 1988.
Due to the prevalence of a dry continental airstream in the latter part of the month, October 2010 was also drier than usual. The total rainfall for the month was 22.7 millimetres, only about 15 percent of the normal figure of 151.9 millimetres. However, the accumulated rainfall total since January 1 stood at 2311.1 millimetres, very close to the normal figure of 2313.1 millimetres for the same period.
Under the influence of a fresh northeast monsoon, the weather was mainly fine for the first four days of the month. A tropical depression developed near Hainan Island on October 5, moving slowly over the next two days. It weakened into an area of low pressure on October 7. The outer rainbands associated with the tropical depression and its remnants affected the south China coast and the northern part of the South China Sea, bringing cloudy weather and rain patches to the territory from October 5 to 9.
With the establishment of a ridge of high pressure over southeastern China, easterly winds strengthened locally and the weather was windy and rainy in Hong Kong in the following two days. With the moderation of these easterly winds, local weather was sunny from October 12 to 14. Meanwhile, a cold front formed over northern Guangdong on October 14, crossing the coastal areas of Guangdong the next morning. Local weather turned slightly cooler and there was some rain over the territory on October 15 and 16. The northeast monsoon brought mainly fine and dry weather for the ensuing four days.
On October 18, Super Typhoon Megi developed over the western North Pacific. It weakened into a severe typhoon while crossing the Philippines on the same day. After entering the South China Sea, Megi drifted generally westwards on October 19 and turned northwards the next day, moving towards the south China coast. Under the combined effect of the northeast monsoon and Megi, local weather became cloudy with showers and there were fresh to strong gusty northerly winds with occasional gales on high ground on October 21. While Megi skirted about 400 kilometres east of Hong Kong and weakened into a typhoon, local winds moderated gradually and it remained cloudy with showers on October 22.
Dominated by a dry continental airstream, the weather in Hong Kong turned mainly fine and dry for the ensuing three days. An intense northeast monsoon reached the south China coast on the morning of October 26. Affected by the intense northeast monsoon, local temperatures dropped progressively, decreasing to a minimum of 15.7 degrees on October 28, the lowest of the month. The weather was fine and very dry with occasional strong winds on high ground and offshore on October 27 and 28. Cool and very dry conditions persisted for the last three days of the month.
Four tropical cyclones occurred over the western North Pacific and the South China Sea during 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 October norms are tabulated in Table 2.
Ends/Tuesday, November 2, 2010
Issued at HKT 19:32
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