2 December 2021

With dry northeast monsoon dominating over southern China for most of the time in the month, November 2021 was marked by dry and sunny weather in Hong Kong. The monthly total sunshine duration amounted to 233.3 hours, 35 percent above the normal of 172.3 hours (or 30 percent above the 1981-2010 normal of 180.1 hours). The monthly rainfall was only 5.8 millimetres, about 15 percent of the normal figure of 39.3 millimetres (or about 15 percent of the 1981-2010 normal of 37.6 millimetres). The accumulated rainfall up to November this year was 2287.6 millimetres, a deficit of 5 percent as compared with the normal of 2402.4 millimetres (or 4 percent below the 1981-2010 normal of 2371.7 millimetres) for the same period. The monthly mean temperature of 22.4 degrees was near the normal figure of 22.2 degrees (or 0.6 degrees above the 1981-2010 normal). Mainly attributing to the exceptionally hot weather in September 2021, the autumn of this year from September to November was much warmer than usual with the mean temperature reaching 26.0 degrees, the third highest on record for the same period.

Under the influence of a fresh to strong easterly airstream, apart from a few light rain patches on the morning of 1 – 3 November, the weather of Hong Kong was generally fine on the first five days of the month. With abundant sunshine and local winds moderating, it was rather warm during the day on 6 – 7 November. The temperatures at the Hong Kong Observatory rose to a maximum of 29.2 degrees on 6 November, the highest of the month.

A cold front moved across the coastal areas of Guangdong on the morning of 8 November. With winds strengthening from the north and a few rain patches, local temperatures fell significantly on the morning of 8 November. Under the influence of the associated dry northeast monsoon, the weather turned fine and dry during the day on that day. Dominated by the dry northeast monsoon and the subsequent replenishment, the weather was generally fine and dry on 9 – 18 November. There were cool mornings on 9 – 10 November and the weather was very dry during the day on 9 – 13 November. The northeast monsoon over the coast of Guangdong was replaced by an easterly airstream on 19 November. Locally, there were a few rain patches in the morning and sunny intervals during the day on that day. Apart from a few rain patches in the morning, the weather turned mainly fine on 20 November. The easterly airstream abated gradually on the next day and there were sunny periods during the day.

Another cold front moved across the coastal areas of Guangdong on the morning of 22 November. Affected by the northeast monsoon associated with the cold front and a broad cloud band over the South China coast, the weather of Hong Kong became cloudy and cool with a few rain patches on 22 – 23 November. The temperatures at the Observatory dropped to 14.3 degrees on the morning of 23 November, the lowest of the month. Under the influence of the dry northeast monsoon and with the thinning out of the cloud band, the weather turned generally fine and dry during the day on 24 November and remained so till the end of the month.

One tropical cyclone occurred over the South China Sea and the western North Pacific in November 2021.

Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.2.  Monthly meteorological figures and departures from normal for November are tabulated in Table 2.