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    The Weather of March 2014

        March 2014 was characterized by gloomy weather during the first-half of the month and heavy rain episodes towards the end of the month.  While the monthly total duration of bright sunshine of 86.0 hours was slightly below normal by 5 percent, there were only 5.0 hours of bright sunshine from 1 to 15 March.  

        The month was also cooler and wetter than usual.  The monthly mean temperature of 18.7 degrees was 0.4 degree below the normal figure of 19.1 degrees.  The total rainfall of the month was 207.6 millimetres, more than double of the normal figure of 82.2 millimetres.  About 99 percent of the monthly rainfall fell between 29 and 31 March.  The accumulated rainfall of 247.1 millimetres since 1 January was about 53 percent above the normal figure of 161.3 millimetres for the same period. 

        Under the influence of a maritime airstream, the weather in Hong Kong was cloudy and humid with fog on the first day of the month.  A cold front moved across the coast of Guangdong on the morning of 2 March.  Local winds strengthened from the east with a few rain patches that afternoon.  Following the passage of the cold front and with subsequent replenishments of the northeast monsoon, the weather in Hong Kong was cool, gloomy and occasionally windy with a few rain patches from 3 to 11 March.  Temperatures at the Hong Kong Observatory dropped to a minimum of 13.9 degrees on the morning of 10 March, the lowest of the month. 

       With the return of a maritime airstream, local weather became humid with rain and fog patches on 12 March.  As a cold front approached the coast of Guangdong, it started off foggy on the morning of 13 March, but the visibility improved gradually as drier continental air took over in the day time.  The northeast monsoon brought cooler weather to Hong Kong with rain patches over the next two days.  

        With the moderation of the northeast monsoon, there were sunny periods on 16 March.  A maritime airstream again brought humid and foggy weather with warmer temperatures in the ensuing four days.  The visibility at Waglan Island once fell below 100 metres on the morning of 19 March.

        But the battle between the cooler continental air and warmer maritime air continued as the passage of another cold front on the evening of 20 March brought fine and dry weather from 21 to 24 March.  Then it was the turn of maritime air to bring warm and humid conditions with coastal fog from 25 to 27 March.   Temperatures at the Hong Kong Observatory rose to a maximum of 27.6 degrees on 27 March, the highest of the month.

        An easterly replenishment of cooler air led to cooler, humid and foggy weather on 28 March.  Meanwhile, the convergence of contrasting air masses near the Pearl River Delta intensified as a trough of low pressure approached the coast of Guangdong. Showers and thunderstorms started to affect Hong Kong on 29 March, and became even more intense on the evening of 30 March.  Over a period of 3 to 4 hours, more than 100 millimetres of rainfall were recorded in Kowloon and the New Territories.  Rainfall in Yuen Long, Tuen Mun, Tsuen Wan and Shatin exceeded 150 millimetres.  The hourly rainfall of 56 millimetres recorded at the Hong Kong Observatory between 9 and 10 p.m. on 30 March was the highest in March since record began in 1884.  The Black Rainstorm Warning was issued at 8:40 p.m., the first time in March since the Rainstorm Warning System commenced operation in 1992.  There were flooding reports in Kowloon and the New Territories including the MTR stations at Kowloon Tong and Wong Tai Sin.  Intense thunderstorms also brought widespread hail and severe squalls to the territory.  A maximum gust exceeding 130 kilometres per hour was reported at Lau Fau Shan, and one person was injured as stacked containers at the Kwai Chung Container Terminals toppled over.  Outbreaks of heavy rain and squally thunderstorms continued throughout the night as the unsettled weather persisted till the end of the month.



    Daily Rainfall Map for 30 March 2014 
    Daily rainfall map for 30 March 2014


     Radar image showing heavy rain and hail-bearing thunderstorms crossing the territory  
    Radar image showing heavy rain and hail-bearing thunderstorms crossing the territory at 8:00 p.m. on 30 March 2014


    A hail stone was picked up in Tsuen Wan 
    A hail stone picked up in Tsuen Wan at around 8:40 p.m.
    on 30 March 2014 (Courtesy of Ms Susanna Cheung)


     

        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 1.6.  Monthly meteorological figures and departures from normal for March are tabulated in Table 2.


     

    Warnings and Signals issued in March 2014


    Table 1.1   Strong Monsoon Signal

    Beginning Time Ending Time
    Day/Month HKT Day/Month HKT
    3 / 3 0800 4 / 3 0300
    6 / 3 0225 8 / 3 0930
    10 / 3 0345 11 / 3 1205
    11 / 3 2235 12 / 3 0545
    20 / 3 2120 21 / 3 1015
    30 / 3 1945 31 / 3 1035


    Table 1.2   Rainstorm Warning Signals

    Colour Beginning Time Ending Time
    Day/Month HKT Day/Month HKT
    Amber 29 / 3 1110 29 / 3 1220
    Amber 30 / 3 1945 30 / 3 2015
    Red 30 / 3 2015 30 / 3 2040
    Black 30 / 3 2040 30 / 3 2230
    Amber 30 / 3 2230 31 / 3 0150
    Amber 31 / 3 0840 31 / 3 1140


    Table 1.3   Landslip Warning

    Beginning Time Ending Time
    Day/Month HKT Day/Month HKT
    30 / 3 2350 31 / 3 0500
    31 / 3 0915 31 / 3 1530


    Table 1.4   Thunderstorm Warning

    Beginning Time Ending Time
    Day/Month HKT Day/Month HKT
    29 / 3 0706 29 / 3 1330
    29 / 3 1450 29 / 3 1630
    30 / 3 0345 30 / 3 0600
    30 / 3 1720 31 / 3 0400
    31 / 3 0750 31 / 3 1400
    31 / 3 1450 1 / 4 0200


    Table 1.5   Fire Danger Warnings

    Colour Beginning Time Ending Time
    Day/Month HKT Day/Month HKT
    Yellow 15 / 3 1200 16 / 3 2000
    Yellow 22 / 3 0600 23 / 3 2110


    Table 1.6   Special Announcement on Flooding
    in the Northern New Territories

    Beginning Time Ending Time
    Day/Month HKT Day/Month HKT
    30 / 3 2020 31 / 3 0230


    Table 2   Figures and Departures from Normal - March 2014

    Meteorological Element Figure of the Month Departure from Normal*
    Mean Daily Maximum Air Temperature 20.9 degrees C 0.5 degree below normal
    Mean Air Temperature 18.7 degrees C 0.4 degree below normal
    Mean Daily Minimum Air Temperature 17.0 degrees C 0.2 degree below normal
    Mean Dew Point Temperature 15.7 degrees C normal
    Mean Relative Humidity 83 % 1 % above normal
    Mean Cloud Amount 77 % 2 % below normal
    Total Rainfall 207.6 mm 125.4 mm above normal
    Number of hours of Reduced VisibilityΔ 59 hours 63.7 hours below normal§
    Total Bright Sunshine Duration 86.0 hours 4.8 hours below normal
    Mean Daily Global Solar Radiation 9.58 Megajoule / square metre 0.38 Megajoule below normal
    Total Evaporation 72.0 mm^ 1.5 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 2013

      ^   Total for 30 days

    daily values of selected meteorological elements for HK for March 2014

    The percentile map of mean temperature of March 2014

      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



     
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