For the month of June, all parts of Singapore received below average rainfall. Subsequently, presence of dry air mass and strong winds helped to subdue weather activities, resulting in fair and warm days between 12 and 19 June. A “Sumatra” squall on the morning of 9 June brought highest rainfall of 104.2mm to Choa Chu Kang and gusty winds up to 37 knots to Jurong areas. This in turn caused the surface winds over Singapore and our vicinity to blow predominantly from the southeast or southwest, signifying the start of the Southwest Monsoon season.Įarly June saw thundery showers mainly in the morning and early afternoon. The above average rainfall was likely influenced by the passage of a Madden-Julian Oscillation (MJO) wet phase over the Maritime Continent.ġ.3 Southwest Monsoon Season (mid-May – mid October)Īround second half of May 2012, the cooling of the Australian landmass in the southern hemisphere resulted in the intensification of the high pressure systems there. The total rainfall amount recorded at the Changi weather station in April and May was 45% - 55% above average. The overall rainfall in April and May was above average. The most intense squall occurred on 5 May, leading to a high rainfall amount of 131.8mm recorded in northern part of Singapore. During the first half of May 2012, temporary incursion of south-westerly winds resulted in a series of “Sumatra” squalls on 5-7 May. The intense thunderstorm on that day caused flash floods around Hougang, Paya Lebar, Macpherson, Tampines and Seletar areas. There were six days in April which saw intense afternoon thunderstorms, with the highest rainfall of 104.2mm recorded on 10 April near Admiralty. An un-seasonal Typhoon Pakhar triggered off an intense “Sumatra” Squall the morning on 1 April. “Sumatra” squall developed mainly during the predawn and morning period on four days in April and ten days in May. The highest maximum temperature for the season was 34.9 0C observed at Paya Lebar on 8 May. Daytime temperature soared to slightly above 34 0C on several days in April and May. Solar heating was also an indispensable ingredient for heavy thunderstorms. It can be attributed to the convergence between the north-easterly winds that strengthened over the South China Sea and the local sea breezes. Afternoon thundery showers were seen on most days and were particularly intense on 25, 27 and 30 March. In late March, low level winds over Singapore weakened, signifying the start of the Inter-Monsoon period. ![]() ![]() In February 2012, there were only 10 rain days with a total rainfall of 83.6mm recorded at the climate station in Changi.ġ.2 First Inter-Monsoon Season (late March – mid-May) This resulted in periods of showers on 14 March from the early hours till morning.ĭespite the heavy showers, Singapore experienced below average rainfall for most parts of the island in January and February 2012. Pressure gradient over the southern China strengthened on 10-14 March. The first week saw mostly isolated afternoon thundery showers, but on 8 and 9 March squall lines affected Singapore in the early hours due to an intrusion of strong westerly winds (20/25 knots) at the 850 mb level feeding into the deepening southern monsoon trough. ![]() The influence of Northeast Monsoon persisted during the first fortnight of March. During the event, rainfall of 102.6 mm (highest daily total for the month) fell over Ulu Pandan where flash flood was reported. An episode of localised intense thunderstorm in the morning over the south western part of Singapore took place on 27 February. While it is generally dry, localised intense weather is still possible. Mainly dry and occasional windy conditions were observed. Towards the end of January, the monsoon trough migrated southward and hovered between the equator and 150S.ĭuring the second week of February, generally fair weather conditions were experienced under the influence of cross-equatorial and diffluent flow. The heavy rain on 20 January caused flash floods in Little India and Thomson Road. The passage of “Sumatra” squalls as well as the convergence of winds and intense solar heating of land areas contributed to a few episodes of heavy thundery showers on 15, 20 and 21 January. This is the third surge for the season with previous 2 episodes taking place in December 2011. A weak monsoon surge affected the region on 7-9 January 2012. 1.1 Northeast Monsoon Season (Jan – late March)Ģ012 started off with moderate Northeast Monsoon conditions prevailing in January, with the surface winds blowing predominantly from the north-northwest and north-northeast.
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