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November 2009 was cooler than usual. The mean temperature of the month was 20.5 degrees, 0.9 degrees below the normal of 21.4 degrees. The first cold day with daily minimum temperature of 12.0 degrees or below occurred on November 17 and was the earliest for winter since 1981. The total rainfall of 60.4 millimetres in the month was about 72% above the normal of 35.1 millimetres. The accumulated rainfall since January 1 was 2132.1 millimetres, about 9% below the normal figure of 2348.2 millimetres for the same period.
The month started with a fine and hot day. A cold front over northern Guangdong moved across the south China coastal areas that evening. Under the influence of an intense northeast monsoon behind the cold front, local weather was windy, dry and cooler with minimum temperatures falling below 20 degrees from November 2-4. As the northeast monsoon weakened, it became warmer with sunny periods for the ensuing three days.
With a warm maritime airstream dominating over the south China coastal areas, local weather turned mainly cloudy with a few light rain patches from November 8-11. Meanwhile, another cold front had formed over southern China and moved across Hong Kong late on November 12, bringing occasional rain. The northeast monsoon behind the cold front brought noticeably cooler weather with some rain to the territory for the next three days.
An intense surge of northeast monsoon reached the south China coastal areas on November 16. Locally, it was rainy in the morning and the temperature started to fall significantly during the day. Winds strengthened on November 17 and the weather became cold. The temperature recorded at the Hong Kong Observatory fell to a minimum of 9.7 degrees on November 18, the lowest of the month. With the northeast monsoon persisting over the south China coast, local weather remained rather cold and dry for the following three days.
With moderation of the northeast monsoon, temperatures started to rise gradually on November 22. It remained mainly fine from November 23-28. A weak replenishment of the northeast monsoon reached the south China Coastal areas on November 29 and brought slightly cooler weather to Hong Kong for the last two days of the month.
Six tropical cyclones occurred over the western North Pacific and the South China Sea in 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 normal of November are tabulated in Table 2.
Ends/Wednesday, December 2, 2009
Issued at HKT 18:42
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