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Singapore in Numbers - Weather

Source:  Straits Times 8 Jan 2018

Singapore experienced a spate of flooding in the last 1-2 years. Most notably on January 8 2018, where 118.8mm of rain fell in a four hour period between 6:20am and 10:25am (roughly half of the average monthly rainfall in January); which overwhelmed drainage infrastructure and led to flash floods in 9 locations across the east of Singapore. While no drainage infrastructure can be designed to be 100% flood free, the public perception is that it has been happening a little too often; not to mention the damage and inconvenience it causes for the locals. It prompted FYT to explore if such floods were indeed coincidence or could there be more to it?

For purposes of this analysis, historical data (2014-2017) from the Singapore Meteorological Services for two stations were used – Tai Seng and East Coast Parkway. As one would expect, the daily rainfall patterns were quite erratic; Singapore would go through periods with little to no rain for many days, periods with sporadic rain days and periods where it rained daily. Despite the variation in data, some observable patterns emerged from the sizable data set. The data suggested that

  • Daily rain fall was gradually increasing over time; though in very small amounts.

  • Roughly in the order of 0.002mm per day

  • Consistent across both stations – Tai Seng and East Coast Parkway

  • Has been as high as 94.6mm in February 19, 2016

  • The variability in daily rainfall was also increasing over time

  • This is observable through the wider range of daily rainfall as well as the higher standard deviations each year

While insightful this evidence is probably not conclusive. Most flood events in Singapore cited the high rainfall in very short periods as the root cause. Incidentally, the Singapore Meteorological Service publishes such data starting in 2014. Data suggests that

  • 30 min peak rainfall have been known to be as high 53.8mm; or more than half the peak daily rainfall in the last 4 years

  • 60 and 120 min peak rainfall have been known to be as high 76-83mm; which is almost the peak daily rainfall in the last 4 years

  • Most notably, standard deviation of the peak rainfalls (30, 60 and 120 min) were increasing. Based on this trend alone, it suggests that Singapore could expect more erratic peak rainfall patterns in the foreseeable future; and until the drainage infrastructure copes, Singapore would also expect the occasional flash flood.

This article is not intended to assess the adequacy of Singapore’s drainage infrastructure nor it is intended to

provide evidence of climate change in Singapore; it is, however, intended to illustrate the power of informed over uninformed opinions and the ease with which this could be accomplished.

While the topic of rainfall and flooding is certainly not earth shattering, but in the world of fake news and alternative facts, it is increasingly important to sort the facts from fiction. If you’re interested in the topic or want to find out more about analytics, please feel free to contact FYT Consulting.

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