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  • The Weather of March 2018

  • 4 April 2018

    March 2018 was unseasonably warm and sunny with little rain. The total duration of bright sunshine of 196.2 hours in the month was more than twice the normal of 90.8 hours and was the highest on record for March. The monthly mean temperature was 20.8 degrees, 1.7 degrees higher than the normal of 19.1 degrees and one of the fourth highest on record for March. The total rainfall in the month was 22.7 millimetres, only about 28 percent of the normal of 82.2 millimetres. The accumulated rainfall of 89.4 millimetres since 1 January was about 45 percent below the normal of 161.3 millimetres for the same period.

    Affected by a mild and humid maritime airstream over the coast of Guangdong, the weather in Hong Kong was warm and foggy with sunny periods in the early part of the month, with conditions turning cloudy on 3 – 4 March and visibility in the harbour falling below 1000 metres in fog. There were also a few showers and isolated thunderstorms on the morning of 4 March. After another foggy morning on 5 March, the weather turned fine and rather warm during the day.

    A cold front moved across the coast of Guangdong on the night of 5 March. Windy conditions under the influence of a strong easterly airstream cleared away the lingering fog patches, and the weather in Hong Kong turned cloudy and appreciably cooler with light rain patches over the next couple of days. Rain associated with the passage of another cold front on the morning of 8 March made up most of the rainfall for the month, and under strengthening northerly winds, temperatures plummeted during the day with temperature at the Hong Kong Observatory reaching a minimum of 11.1 degrees, the lowest of the month, on the morning of 9 March. The cold air mass of continental origin also brought drier conditions and the weather turned sunny during the day.

    A spell of fine weather with abundant sunshine then persisted till 13 March, with winds turning easterly and temperature gradually on the rise. With a humid maritime airstream pushing back towards the coast of Guangdong, the weather became cloudy with light rain patches on 14 March. The weather turned fine and warm over the next couple of days apart from some morning fog on 16 March.

    A fresh to strong easterly airstream brought slightly cooler weather and light rain patches to the territory on 17 March. With the easterly winds moderating over the next couple of days, the weather in Hong Kong became warm with some mist patches early on 19 March. The passage of a cold front on the morning of 20 March brought cooler weather and a dry northeast monsoon to the coastal areas of Guangdong. Sunny weather prevailed in Hong Kong over the next three days, with daytime relative humidity falling below 40 percent on 21 March.

    Winds gradually turned easterly and moister air of maritime origin brought cloudier skies on 24 March. A weak northeast monsoon then generally prevailed over the coast of Guangdong over the next few days and despite a replenishment of easterly winds towards the end of the month, the weather remained generally fine and warm in Hong Kong. With abundant sunshine, temperature at the Hong Kong Observatory climbed to the month’s highest of 27.9 degrees on 30 March.


Sea fog over Victoria Harbour on 3 March 2018
Sea fog over Victoria Harbour on 3 March 2018



Sea fog near Tseung Kwan O on 5 March 2018
Sea fog near Tseung Kwan O on 5 March 2018


     One 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 March are tabulated in Table 2.
 

Warnings and Signals issued in March 2018

Table 1.1   Strong Monsoon Signal
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
6 / 3 0630 7 / 3 0745
8 / 3 1045 8 / 3 1610
17 / 3 0345 17 / 3 1510
21 / 3 0140 21 / 3 0740


Table 1.2   Thunderstorm Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
4 / 3 0840 4 / 3 1140
19 / 3 1800 19 / 3 2000


Table 1.3   Fire Danger Warnings
Colour Beginning Time Ending Time
Day/Month HKT Day/Month HKT
Red 9 / 3 0600 9 / 3 2310
Yellow 10 / 3 0730 10 / 3 2100
Yellow 11 / 3 0600 11 / 3 1900
Yellow 18 / 3 0600 18 / 3 1800
Red 21 / 3 0600 23 / 3 2145
Yellow 25 / 3 1030 25 / 3 2145
Yellow 30 / 3 0600 30 / 3 1845
Red 31 / 3 0600 31 / 3 1945


Table 1.4   Cold Weather Warning
Beginning Time Ending Time
Day/Month HKT Day/Month HKT
8 / 3 0600 9 / 3 1100


Table 2   Figures and Departures from Normal - March 2018
Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 24.4 degrees C 3.0 degrees above normal
Mean Air Temperature 20.8 degrees C 1.7 degrees above normal
Mean Daily Minimum Air Temperature 18.6 degrees C 1.4 degrees above normal
Mean Dew Point Temperature 16.2 degrees C 0.5 degree above normal
Mean Relative Humidity 76 % 6 % below normal
Mean Cloud Amount 56 % 23 % below normal
Total Rainfall 22.7 mm 59.5 mm below normal
Number of hours of Reduced VisibilityΔ 13 hours 99.1 hours below normal§
Total Bright Sunshine Duration 196.2 hours 105.4 hours above normal
Mean Daily Global Solar Radiation 16.55 Megajoule / square metre 6.59 Megajoule above normal
Total Evaporation 96.2 mm 25.7 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.
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 2017

daily values of selected meteorological elements for HK for March 2018

The percentile map of mean temperature of March 2018

  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 2018