The monsoon this December in Singapore has been quite pleasant and nicely marked the year’s passage. But I am sure some have suffered the relentless downpour on certain days that are described as monsoon surges.
The info below taken from the weather.gov.sg FAQ site
Singapore has two main seasons, the Northeast Monsoon (December to March) and the Southwest Monsoon season (May to September), separated by two relatively shorter inter-monsoon periods. Although there are no distinct wet or dry periods, the mean monthly rainfall shows drier weather conditions from May to July and wetter conditions in the months from November to January. . February is also a relatively dry month. The beginning and end of the monsoons are usually not very well-defined. Hence, from year to year, there could be slight delay in the beginning or end of a monsoon period. This probably accounts for the monthly rainfall anomaly experienced from year to year.
Sumatras are line of thunderstorms which usually occur during the Southwest Monsoon season from May to October each year. These squalls develop at night over Sumatra or the Malacca Straits and move east towards Singapore and the west coast of Peninsular Malaysia during the pre-dawn and early morning. They are often characterised by sudden onset of strong gusty surface winds and heavy rain lasting from 1 to 2 hours as they move across the island. Maximum gusts of up to 50 knots have been recorded during the passage of a Sumatra squall.
This below is from the Monsoon update page from the weather.gov.sg
(Updated on 27 December 2011)
Northeast Monsoon conditions have set in over the region since mid-November 2011. The Northeast Monsoon season typically starts with a wet phase (December to January) followed by a dry phase (February to early March). During the wet phase, the Northeast Monsoon season is characterized by short duration thundery showers in the afternoon and early evening, and about two to four episodes of monsoon surges. Monsoon surges refer to the steady strengthening of northeasterly winds blowing from the South China Sea. These monsoon surges usually bring periods of prolonged widespread moderate to heavy rain lasting two to five days, occasionally windy conditions and cooler temperatures. During the dry phase, generally drier and windy conditions can be expected.
Based on long-term statistics from our climate station, December is the wettest month of the year (287.4 mm), followed by November (255.9 mm) and January (241.3 mm) respectively. The mean daily minimum temperature is lowest for January (23.3 deg Celsius), followed by December (23.5 deg Celsius) and February (23.6 deg Celsius).
The monsoon surge which has been affecting the region for the past several days has eased. Windy conditions and passing showers in the afternoon are forecast for the next two days. Short duration thundery showers in the afternoon can be expected for the rest of the week.