The Weather of March 2013

     With sunnier than usual weather and frequent visit of the warm maritime airstream, March 2013 was much warmer than usual.  The mean temperature of 20.5 degrees for the month was 1.4 degrees above normal and the eighth warmest for March.  Moreover, the monthly mean maximum temperature of 23.5 degrees was the fourth highest on record for March.  Mainly due to the prolonged fine weather in the first half of the month, the total bright sunshine duration in March 2013 was 127.4 hours, about 40 percent above normal. 

     The rainfall deficit since January was partly compensated by the rainy weather in the latter part of March.  The monthly rainfall of March 2013 was 130.5 millimetres, about 59 percent above the normal figure of 82.2 millimetres.  The accumulated rainfall since 1 January 2013 was 135.4 millimetres, about 16 percent below the normal figure of 161.3 millimetres for the same period.

     Under the influence of a humid maritime airstream, the weather in Hong Kong was mainly cloudy with light rain patches and fog for the first day of the month.  Visibility at Waglan Island fell below 100 metres that night.  A cold front crossed the coast of Guangdong in the morning on 2 March, bringing windy and appreciably cooler weather to the territory.  There were also a few rain and mist patches on that day.  The intense northeast monsoon behind the cold front maintained rather cool weather on the morning of the next two days.  The temperatures at the Observatory fell to a minimum of 13.2 degrees on the morning of 4 March, the lowest of the month. With the dry northerly airstream clearing the sky, local weather turned fine and very dry on 4 and 5 March.  Under the prevalence of a dry continental airstream, local weather stayed sunny and dry for the ensuing five days.

     There were light rain and mist patches in the morning and sunny periods in the afternoon in Hong Kong on 11 and 12 March.  With sunny periods and light wind condition during the day, it was warm on 13 March.  A cold front formed over inland Guangdong crossed the coast of Guangdong the next morning.  The associated northeast monsoon brought cooler weather to the territory on 14 and 15 March. 

     With a ridge of high pressure establishing over southeast China, the weather in Hong Kong became generally fine on 16 March.  Under the influence of a maritime airstream, it was mainly cloudy with mist and coastal fog on the next two days.  

     A trough of low pressure developed over the south China coastal areas and brought heavy rain and squally thunderstorms to Hong Kong in the afternoon on 19 March.  More than 30 millimetres of rainfall were recorded at Lantau Island and even over 40 millimetres were recorded at Hong Kong Island.  Small pea size hail was reported at the Peak in Hong Kong Island and Clear Water Bay in Sai Kung during the passage of the intense thunderstorms.  Affected by the light southerly airstream, local weather was mainly cloudy and warm on 20 March with temperatures at the Observatory rising to a maximum of 28.3 degrees in the afternoon, the highest of the month.

     A fresh easterly airstream reached the coast of Guangdong on the morning of 21 March.  Local weather became cooler with rain patches and mist on that day.  With the setting in of a warm and humid maritime airstream, it was cloudy with coastal fog for the next three days.  An intense northeast monsoon reached the coastal areas of Guangdong on 25 March and brought cooler weather to the region. Locally it was also windy with light rain patches and coastal fog on that day. 

     A cold front formed over inland Guangdong in the afternoon on 26 March and swept across the coastal areas that evening.  The associated heavy rain and thunderstorms affected Hong Kong in the afternoon and brought more than 20 millimetres of rainfall to many places with more than 50 millimetres recorded over Tuen Mun.  Local weather remained unsettled with showers and thunderstorms the next day. 

     Affected by a trough of low pressure, there were occasional heavy showers with squally thunderstorms on 28 March.  More than 30 millimetres of rainfall were generally recorded over the territory on that day.  With the dissipating of the trough of low pressure, the rain eased off gradually the next day but there were still some thunderstorms in the morning.  Affected by the northeast monsoon together with another trough of low pressure, local weather became windy and unsettled on 30 March.  The thundery showers brought more than 50 millimetres of rainfall to Hong Kong Island, Lantau Island and parts of Lamma Island in that afternoon.  It remained cloudy with a few rain patches on the last day of the month.

Radar echoes were captured at 5:18pm on 19 March 2013.

     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.