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  • The Weather of March 2019

  • 2 April 2019

    As the northeast monsoon over southern China was weaker than normal for most of the time in the month, March 2019 continued to be much warmer than usual in Hong Kong with a mean temperature of 21.0 degrees, 1.9 degree above the normal of 19.1 degrees and the fourth highest on record for March. The mean minimum temperature of the month was 19.4 degrees, 2.2 degrees above normal of 17.2 degrees and the third highest on record for March. Moreover, for the first quarter (January to March) of 2019, the mean temperature of 19.7, mean maximum temperature of 22.1 and mean minimum temperature of 18.1 were all the highest on record for the same period. Affected by troughs of low pressure over the coastal areas of Guangdong in the early part of the month, the weather of Hong Kong was also wetter than usual in March 2019. The total rainfall of 186.5 millimetres in the month was more than twice the normal of 82.2 millimetres. The accumulated rainfall recorded in the first three months of the year was 259.9 millimetres, nearly 61 percent above the normal figure of 161.3 millimetres for the same period.

    Dominated by a fresh to strong easterly airstream, the weather of Hong Kong was cloudy with a few light rain patches on the first day of March. While the easterly airstream was gradually replaced by a maritime airstream, local weather improved with sunny periods on 2 March. There was coastal fog at first on 3 March with the visibility at Waglan Island falling below 1000 metres. Meanwhile, a cold front moved across the coast of Guangdong in the morning and brought some showers to many places of the territory. Affected by the northeast monsoon behind the cold front and the showery activities along the coastal areas, local weather was a mixture of sunny intervals and thundery showers on 4 - 5 March.

    Under the influence of a trough of low pressure lingering over the coastal areas of Guangdong, it was cloudy with occasional showers and thunderstorms on 6 - 7 March. The showers were particularly heavy on 6 March with 45.5 millimetres of rainfall recorded at the Observatory, making it the wettest Insects Waken on record. Rainfall over Kowloon and Lantau Island even exceeded 70 millimetres on that day. With the setting in of a strong easterly airstream, local weather became cooler with a few showers on 8 March. Under the rain, the temperature at the Observatory dropped to a minimum of 15.1 degrees, the lowest of the month. Affected by another trough of low pressure over the South China coast, the weather in Hong Kong remained cloudy and cool with a few showers on 9 - 10 March.

    Under the influence of a dry northeast monsoon, apart from a few rain patches in the morning, the weather of Hong Kong turned generally fine on the afternoon of 11 March and remained so in the next day. With the strengthening of the easterlies, local weather became windier with a few showers on 13-15 March. A dry northeast monsoon brought sunny periods to Hong Kong again on 16 - 18 March.

    With the northeast monsoon over the coast of Guangdong moderating gradually and being replaced by a warm maritime airstream, the weather of Hong Kong became warm with rather low visibility on 19 - 22 March. Coastal fog on the mornings of 21 and 22 March brought the visibility down to below 1000 metres at Waglan Island. It was very warm on 22 March with the daily minimum temperature of 24.8 degrees recorded at the Observatory, one of the highest on record for March.

    Meanwhile, a cold front moved across the coast of Guangdong on the night of 22 March. The associated northeast monsoon brought cooler and rainy weather to Hong Kong in the next three days. Affected by a fresh easterly airstream, apart from a few light rain patches on the morning of 27 March, it was mainly cloudy with sunny intervals on 26 - 27 March. With the return of a warm maritime airstream, the weather of Hong Kong became very warm with morning coastal mist on 28 March. With plenty of sunshine in the afternoon, the maximum temperature at the Observatory soared to 27.8 degrees on that day, the highest of the month. Apart from coastal fog in the morning, the weather remained warm with sunny interval on the afternoon of 29 March. Affected by an area of thundery showers associated with an upper-air disturbance, there were also some showers and a few thunderstorms in that evening. With a surge of the northeast monsoon reaching the coast of Guangdong on the morning of 30 March, local weather became windier and slightly cooler with a few showers towards the end of the month.

    There was no tropical cyclone 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 March are tabulated in Table 2.
 

Warnings and Signals issued in March 2019

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
4 / 3 2330 5 / 3 0745
7 / 3 2015 9 / 3 0230
31 / 3 0715 1 / 4 1500


Table 1.2   Rainstorm Warning Signals
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Amber 6 / 3 1135 6 / 3 1520


Table 1.3   Thunderstorm Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
3 / 3 0710 3 / 3 0930
4 / 3 2230 5 / 3 0330
6 / 3 0945 6 / 3 1630
29 / 3 1730 29 / 3 1930


Table 1.4   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Yellow 16 / 3 0740 17 / 3 1800


Table 2   Figures and Departures from Normal - March 2019
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 23.3 degrees C 1.9 degrees above normal
Mean Air Temperature 21.0 degrees C 1.9 degrees above normal
Mean Daily Minimum Air Temperature 19.4 degrees C 2.2 degrees above normal
Mean Dew Point Temperature 18.2 degrees C 2.5 degrees above normal
Mean Relative Humidity 84 % 2 % above normal
Mean Cloud Amount 81 % 2 % above normal
Total Rainfall 186.5 mm 104.3 mm above normal
Number of hours of Reduced VisibilityΔ 27 hours 80.6 hours below normal§
Total Bright Sunshine Duration 91.3 hours 0.5 hour above normal
Mean Daily Global Solar Radiation 10.13 Megajoule / square metre 0.17 Megajoule above normal
Total Evaporation 65.3 mm 5.2 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.
Before 10 October 2007, the number of hours of reduced visibility at the Hong Kong International Airport in 2005 and thereafter displayed in this web page was based on hourly visibility observations by professional meteorological observers. Since 10 October 2007, the data have been revised using the average visibility readings over the 10-minute period before the clock hour, as recorded by the visibility meter near the middle of the south runway.


  *   Departure from 1981 - 2010 climatological normal, except for number of hours of reduced visibility

  §   Departure from mean value between 1997 and 2018

daily values of selected meteorological elements for HK for March 2019

The percentile map of mean temperature of March 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


Extract of Meteorological Observations in Hong Kong for March 2019