The Weather of October 2018
2 November 2018
With the northeast monsoon successively affecting south China coastal areas, October 2018 was slightly cooler than usual in Hong Kong. The monthly mean temperature of 25.3 degrees was 0.2 degrees below the normal figure of 25.5 degrees. The monthly rainfall was 104.3 millimetres, slightly above the normal of 100.9 millimetres in October. The accumulated rainfall recorded in the first ten months of the year was 2077.6 millimetres, a deficit of 11 percent compared to the normal of 2334.0 millimetres for the same period.
Under the influence of the northeast monsoon, apart from a few morning showers on 1 October, the local weather was generally fine and dry on 1 - 8 October. With abundant sunshine, temperatures at the Hong Kong Observatory rose to 31.4 degrees on the afternoon of 5 October, the highest of the month. Affected by an easterly airstream, there were sunny periods and a few showers on 9 October.
A cold front crossed the coastal areas of Guangdong on the afternoon of 10 October. Heavy showers associated with the cold front brought more than 20 millimetres of rainfall to most parts of the territory in the afternoon, rainfall even exceeded 40 millimetres in the urban areas and Shek Kong. The northeast monsoon brought mainly cloudy and cooler weather as well as a few rain patches to Hong Kong in the next four days. With an easterly airstream setting in, it was cloudy with showers on 15 October.
A weak cold front crossed the coast of Guangdong on the morning of 16 October. The associated northeast monsoon brought some rain and slightly cooler weather to Hong Kong on 16 - 17 October. Under the influence of a strong easterly airstream, it was windy and cooler with rain patches on 18 October. The temperature of the Observatory dropped to 20.9 degrees under the rain on the morning of 18 October, the lowest of the month. Apart from a few rain patches, local weather became gradually brighter during the day on 19 - 20 October.
Dominated by an anticyclone aloft southern China, local weather became generally fine on 21 October and the next morning. With a weak northeast monsoon arriving at the coast of Guangdong on 22 October, local weather turned mainly cloudy with light rain patches in the afternoon and the next two days. Under the influence of anticyclone aloft, the weather in Hong Kong became brighter with sunny periods on 25 - 26 October. A cold front moved across the coastal areas of Guangdong on the night of 26 October. Under the influence of the dry northeast monsoon, the weather in Hong Kong became fine and very dry with cooler mornings on 27 - 30 October. Meanwhile, tropical cyclone Yutu entered the northern part of the South China Sea and edged closer to the coast of Guangdong on 31 October. Locally, it was very dry with winds picking up gradually from the north on that day.
Three tropical cyclone occurred over the South China Sea and the western North Pacific in the month.
Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.4. Monthly meteorological figures and departures from normal for October are tabulated in Table 2.
Warnings and Signals issued in October 2018
| Name of Tropical Cyclone |
Signal Number |
Beginning Time | Ending Time | ||
|---|---|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT | ||
| YUTU | 1 | 31 / 10 | 0840 | 1 / 11 | 1240 |
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 18 / 10 | 2220 | 20 / 10 | 0945 |
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 10 / 10 | 1257 | 10 / 10 | 1600 |
| Colour | Beginning Time | Ending Time | ||
|---|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT | |
| Yellow | 1 / 10 | 0910 | 1 / 10 | 2000 |
| Red | 3 / 10 | 1240 | 3 / 10 | 1940 |
| Red | 4 / 10 | 0800 | 6 / 10 | 2100 |
| Yellow | 7 / 10 | 0600 | 7 / 10 | 1800 |
| Yellow | 14 / 10 | 0740 | 14 / 10 | 1800 |
| Yellow | 21 / 10 | 0745 | 21 / 10 | 1800 |
| Yellow | 27 / 10 | 0600 | 28 / 10 | 0600 |
| Red | 28 / 10 | 0600 | 1 / 11 | 1900 |
| Meteorological Element | Figure of the Month | Departure from Normal* |
|---|---|---|
| Mean Daily Maximum Air Temperature | 28.0 degrees C | 0.2 degree above normal |
| Mean Air Temperature | 25.3 degrees C | 0.2 degree below normal |
| Mean Daily Minimum Air Temperature | 23.4 degrees C | 0.3 degree below normal |
| Mean Dew Point Temperature | 18.7 degrees C | 1.5 degrees below normal |
| Mean Relative Humidity | 69 % | 4 % below normal |
| Mean Cloud Amount | 59 % | 1 % above normal |
| Total Rainfall | 104.3 mm | 3.4 mm above normal |
| Number of hours of Reduced VisibilityΔ | 17 hours | 113.5 hours below normal§ |
| Total Bright Sunshine Duration | 181.9 hours | 12.0 hours below normal |
| Mean Daily Global Solar Radiation | 14.75 Megajoule / square metre | 0.7 Megajoule above normal |
| Total Evaporation | 114.1 mm | 9.8 mm below normal |
| Remarks : | All measurements were made at the Hong Kong Observatory except sunshine,
solar radiation and evaporation which were recorded at King's Park
Meteorological Station and visibility which was observed at the Hong
Kong International Airport. |
| Δ | The visibility readings at the Hong Kong International Airport are based on hourly observations by professional meteorological observers in 2004 and before, and average readings over the 10-minute period before the clock hour of the visibility meter near the middle of the south runway from 2005 onwards. The change of the data source in 2005 is an improvement of the visibility assessment using instrumented observations following the international trend.
|
* Departure from 1981 - 2010 climatological normal, except for number of hours of reduced visibility |
|
§ Departure from mean value between 1997 and 2017 |
|
| Remarks : | Extremely high: above 95th percentile Above normal: between 75th and 95th percentile Normal: between 25th and 75th percentile Below normal: between 5th and 25th percentile Extremely low: below 5th percentile Percentile and 5-day running average values are computed based on the data from 1981 to 2010 |
