A rainy and cool March with warm episodes

     With the northeast monsoon and a humid maritime airstream competing for dominance over the south China coast, March 2016 in Hong Kong was characterised by gloomy, rainy and humid weather with fluctuating temperatures. Overall, the month was cooler than usual with rainfall above normal. The monthly mean temperature was 17.5 degrees, 1.6 degrees lower than the normal figure of 19.1 degrees. The monthly total rainfall was 148.7 millimetres, about 81 per cent more than the normal figure of 82.2 millimetres. The accumulated rainfall of 440.4 millimetres in the first three months of the year was about 2.7 times the normal figure of 161.3 millimetres for the same period.

     Under the influence of a relatively dry northeast monsoon, the weather in Hong Kong was generally fine with cool mornings on the first three days of the month. A humid maritime airstream brought cloudy weather to Hong Kong on March 4 and 5. As the clouds thinned out, sunny periods emerged on March 6 with some mist patches in the morning and temperatures rising to 25.9 degrees in the afternoon, the highest of the month.

     The clouds returned on March 7, and a long spell of gloomy skies and rainy weather persisted for the next 18 days. Foggy conditions affected the coastal waters of Guangdong and visibility at Waglan Island once fell to around 100 metres on March 8 and 9. An intense northeast monsoon following the passage of a cold front on the night of March 9 brought cold weather to Hong Kong over the next couple of days. Temperatures at the Hong Kong Observatory fell to a minimum of 10.0 degrees, the lowest of the month, shortly before midnight on March 10 and during the small hours on March 11. Affected by replenishments of the northeast monsoon and freshening easterly winds, the weather remained generally cool with mist and rain patches till March 17.  

     With the return of a humid maritime airstream, foggy weather affected the south China coast on March 18 and 19. Visibility at Waglan Island dropped to around 100 metres. The weather became warmer as temperatures climbed. The approach of a trough of low pressure and a strengthening easterly airstream on March 21 brought more unsettled conditions and squally thunderstorms. More than 40 millimetres of rainfall were generally recorded over the territory that day. Rainy weather and overcast skies with fog patches and thunderstorms continued to affect Hong Kong over the next couple of days.

     The passage of a cold front on March 24 brought rainy and appreciably cooler conditions to Hong Kong.  After a cold morning on March 25, the arrival of a dry continental air mass finally cleared away the clouds.  Fine and sunny weather prevailed in the next couple of days with the relative humidity falling below 30 per cent on March 27. With the setting in of a mild easterly airstream, generally cloudy weather prevailed over the territory towards the end of the month, and the return of a humid maritime air mass brought mist patches and low visibility to some places on March 30 and 31.

     There was no tropical cyclone over the South China Sea or the western North Pacific in the month.

     Details of issuance and cancellation of various warnings/signals in the month are summarised in Table 1. Monthly meteorological figures and departures from normal for March are tabulated in Table 2.

Ends/Tuesday, April 5, 2016
Issued at HKT 16:59