The Weather of March 2015

    With a maritime airstream dominating over the coast of Guangdong during the latter half of the month, the weather of Hong Kong in March 2015 was warmer than usual.  The monthly mean temperature was 19.9 degrees, 0.8 degrees higher than the normal figure of 19.1 degrees.  The total rainfall in the month was 28.4 millimetres, only about 35 percent of the normal figure of 82.2 millimetres. The accumulated rainfall of 102.1 millimetres since 1 January was about 37 percent below the normal figure of 161.3 millimetres for the same period.

    A cold front over southern China moved across the coastal areas of Guangdong on the first day of the month and the strengthening of an easterly airstream brought cooler weather the next day.  Another replenishment of the northeast monsoon on 4 and 5 March brought windy and even cooler conditions to Hong Kong, and the weather remained cloudy with light rain and mist patches till 8 March.

    Following a lull in the northeast monsoon that brought a warm and sunny day on 9 March, easterly winds strengthened again the next day as another replenishment of the northeast monsoon reached the coast of Guangdong.  The weather became significantly cooler with light rain patches on 10-13 March.  Temperatures at the Observatory fell to a minimum of 14.8 degrees on 12 March, the lowest of the month.

    As the northeast monsoon subsided, it was gradually replaced by a warmer maritime airstream on 14 and 15 March.  Local weather turned increasingly humid with lingering clouds, mist and fog.  As temperatures continued to rise, clouds finally dispersed during the day for some sunshine to break through on 19 March.  Fine weather then prevailed in the next couple of days and temperatures at the Observatory climbed to a maximum of 28.3 degrees on 20 March, the highest of the month. 

    With easterly winds strengthening and the northeast monsoon returning to the coast of Guangdong, the weather turned generally cloudy and windy with light rain patches from 22 to 26 March.  After a rainy morning on 27 March, sunny intervals appeared in the afternoon as warm maritime air set in over the coast of Guangdong.  Despite some coastal mist, clouds thinned out during the day with sunny periods coming through towards the end of the month.

    Two tropical cyclones 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 1.2.  Monthly meteorological figures and departures from normal for March are tabulated in Table 2.