You've probably guessed how this chapter is going to begin, so let's get it over with: "Now a look at tomorrow's weather - you can expect a fine day with showers over several areas in the late morning and early afternoon, the temperature will range between twenty-four and thirty-two degrees."

Why do they bother?

While I can't answer that question, I can answer this: why is Singapore's weather [!] so boringly predictable?

In fact, despite the best efforts of the television weatherman to convince us otherwise, our climate [?] is not absolutely uniform throughout the year. For instance, from November to January, monthly rainfall is usually fifty millimetres higher than in other months. Not surprisingly, it is roughly these same months that experience fewer hours of sunshine per day.

Similarly, and I would argue, more importantly, the rain which does fall is not evenly distributed throughout the island. What is more, the pattern of distribution [!] varies from region [?] to region in Singapore, again depending on the time of year.

This all means that our local weather is actually more interesting than our friendly television weatherman would have us believe.

In order for us to understand these seasonal variations in our local weather, the most suitable approach would be to divide what we know as 'weather' into its constituent aspects.

The strongest wind ever recorded in Singapore was in April 1984, when windspeed reached 144 km/h. According to the Beaufort Scale, this is equivalent to a speed of 78 knots, which is equivalent to hurricane force!

This was unusual in more ways than one, because not only do typical high-speed winds only average around 60 km/h (32 knots), but they generally occur between June and September, during the south monsoon.

Monsoons are large-scale winds which blow in opposite directions at different times of the year. They are caused by the differential rates of heating and cooling of the continents, with respect to the sea.

During the northern hemisphere winter, Central Asia and north-west India lose heat quickly. The air above these landmasses cools, contracts, becomes denser and subsides, forming an area of high pressure. Conversely, as the southern hemisphere is experiencing summer at this time of year, the air over northern Australia warms, expands, becomes less dense and rises, forming an area of low pressure. As winds blow from areas of high to low pressure, the north-east monsoon blows over Singapore.

The situation is of course reversed during the months of June to September, when Singapore experiences the south monsoon.

An important feature during the south monsoon is the 'sumatras', which are line squalls occurring from Singapore northwards up the west coast of Peninsular Malaysia, during the morning hours. Line squalls are storms of short duration, extending along a sharply defined line ahead of a cold front (which, in turn, is the boundary where advancing cold air undercuts and replaces slower moving warm air, forcing the latter to rise).

Strong southerly winds are favourable to sumatra formation, because they promote the uplift of warm air. As a result, sumatras occur just before sunrise till late morning, for about three to four days each month throughout the monsoon season.

Cloud cover throughout the year over Singapore averages six to seven oktas [?] at any time (this is equivalent to 70% to 90% cover). It is least cloudy during February and March, and most cloudy towards the end of the year and early January during the north-east monsoon. Within a twenty-four hour period, it is most cloudy between late morning and early evening, due to high clouds which occur even when the weather is fair.

Records from the Singapore Meteorological Service [!] show that during the day, May is usually the hottest month (31.7 ^oC), while December is the coolest (29.5 ^oC). The high temperatures in April and May are due to the very still wind conditions after the north-east monsoon, which blows between November and January, has dissipated.

Also, each day, it is not hottest at noon, but in the early afternoon. May and June have warm nights, with temperatures averaging 24.2 ^oC. This is due to the retention of long-wave infra-red radiation by the extensive cloud cover in the mid- to late-afternoon at that time of the year.

After May, temperatures are lowered by the south monsoon, as well as by the frequent occurrence of Sumatras which increase cloud cover in the morning and hence reduce incoming ultra-violet solar radiation.

The most comfortable period of the year in Singapore as far as temperatures are concerned is of course during the north-east monsoon, when nights are clear, allowing greater heat loss. This is augmented by steady, cooler northeasterly winds which continue throughout the night. Minimum temperatures at this time of the year average 23.1 ^oC.