Hi, despite the rapid advancement in computational processing technology, mathematical forecasting algorithms / models and meteorology monitoring instrumentation over the past decades. It is still a cat-and-mouse game for meteorologists to predict the exact forecast down to the hour in advance with a high enough degree of geographical resolution.
This is especially so considering the dynamic nature of the InterTropical Convergence Zone (ITCZ) in which the Island of Singapore is located in, whereby weather system can develop and dissipate rapidly thus in fact it is even easier to predict where a topical cyclone (or hurricane) will make landfall than where exactly in Singapore will there be a thunderstorm.