The Weather of January 2020
4 February 2020
With the northeast monsoon over southern China generally weaker than normal for most of the time in the month, January 2020 was much warmer than usual. The mean maximum temperature of 21.2 degrees and mean temperature of 18.6 degrees were respectively 2.6 degrees and 2.3 degrees above their corresponding normals and both were the highest on record for January. The mean minimum temperature of 16.8 degrees was 2.3 degrees above the normal and one of the second highest on record for January. The month was also drier than usual with 14.8 millimetres of rainfall recorded in the month, about 60 percent of the normal figure of 24.7 millimetres.
Under the influence of a fresh to strong northeast monsoon, the weather of Hong Kong was windy and cool with a few rain patches on the morning of the first day of the month. With the northeast monsoon moderating, the covering clouds thinned out gradually and the weather became generally fine on the afternoon of 2 January. An anticyclone aloft southern China maintained the generally fine weather in Hong Kong in the next two days. With the establishment of a ridge of high pressure over southeastern China, local winds strengthened from the east and the weather became mainly cloudy on 5 – 6 January. The weather turned generally fine during the day as winds weakened on 7 January.
A surge of the northeast monsoon reached the south China coastal areas on the morning of 8 January. The weather of Hong Kong remained fine with winds picking up from the east in the afternoon. With plenty of sunshine, the maximum temperature at the Hong Kong Observatory rose to 26.0 degrees, the highest of the month. Under the influence of the fresh to strong northeast monsoon, local weather was slightly cooler with sunny periods on 9 – 10 January. With winds subsiding, visibility over some areas were relatively low during the day on 11 January. A cold front over southern China moved across the coastal areas of Guangdong on that evening and brought cooler mornings to Hong Kong in the next two days.
Under the influence of an easterly airstream, the weather of Hong Kong became fine during the day on 14 January. With the strengthening of the easterly airstream, local weather turned mainly cloudy with a few rain patches on the next two days. Meanwhile, a cold front moved across the coastal areas of Guangdong on the night of 16 January, the associated northeast monsoon brought mainly cloudy weather and cool mornings to Hong Kong on 17 - 21 January. With the northeast monsoon replacing by a maritime airstream, local weather became milder with a few light rain patches and coastal mist and fog on 22 – 24 January. The coastal fog on the morning of 24 January brought the visibility down to around 100 metres at Waglan Island. Affected by rainbands over the south China coast, it was mainly cloudy with a few rain patches in Hong Kong on 25 January.
Meanwhile, a cold front moved across the coastal areas of Guangdong on the night of 25 January. The weather of Hong Kong became mainly cloudy with occasional rain and thunderstorms with about 10 millimetres of rainfall recorded over many places on the morning of 26 January. The associated intense winter monsoon also brought appreciably cooler weather to the territory on that day. With the northerlies prevailing, it was mainly cloudy and cold with a few rain patches on 27 January and on the morning of 28 January. The weather then turned fine and dry on 28 January as the clouds dissipated gradually during the day. The temperatures at the Hong Kong Observatory fell to a minimum of 10.8 degrees on the morning of 28 January, the lowest of the month. Affected by the winter monsoon, local weather remained generally fine and dry with cold mornings till the end of the month.
There was no tropical cyclone over the South China Sea and the western North Pacific in January 2020.
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 January are tabulated in Table 2.
Warnings and Signals issued in January 2020
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 31 / 12 | 1145 | 1 / 1 | 0940 |
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 26 / 1 | 0032 | 26 / 1 | 0330 |
| Colour | Beginning Time | Ending Time | ||
|---|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT | |
| Yellow | 8 / 1 | 1130 | 8 / 1 | 2200 |
| Yellow | 12 / 1 | 1030 | 12 / 1 | 2000 |
| Yellow | 17 / 1 | 0600 | 17 / 1 | 2145 |
| Yellow | 19 / 1 | 0600 | 19 / 1 | 1900 |
| Yellow | 27 / 1 | 0600 | 27 / 1 | 1610 |
| Yellow | 28 / 1 | 1140 | 29 / 1 | 0600 |
| Red | 29 / 1 | 0600 | 31 / 1 | 0745 |
| Yellow | 31 / 1 | 0745 | 31 / 1 | 2355 |
| Beginning Time | Ending Time | ||
|---|---|---|---|
| Day/Month | HKT | Day/Month | HKT |
| 26 / 1 | 1620 | 1 / 2 | 0915 |
| Meteorological Element | Figure of the Month | Departure from Normal* |
|---|---|---|
| Mean Daily Maximum Air Temperature | 21.2 degrees C | 2.6 degrees above normal |
| Mean Air Temperature | 18.6 degrees C | 2.3 degrees above normal |
| Mean Daily Minimum Air Temperature | 16.8 degrees C | 2.3 degrees above normal |
| Mean Dew Point Temperature | 14.0 degrees C | 2.6 degrees above normal |
| Mean Relative Humidity | 76 % | 2 % above normal |
| Mean Cloud Amount | 65 % | 4 % above normal |
| Total Rainfall | 14.8 mm | 9.9 mm below normal |
| Number of hours of Reduced VisibilityΔ | 23 hours | 198.9 hours below normal§ |
| Total Bright Sunshine Duration | 170.7 hours | 27.7 hours above normal |
| Mean Daily Global Solar Radiation | 12.73 Megajoule / square metre | 2.56 Megajoule above normal |
| Total Evaporation | 79.5 mm | 8.2 mm above 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 2019 |
|
| 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 |
