Sunset:  In Brunei, the earliest sunset is on 7th November. Why?

December 21st is the shortest day, but not the earliest sunset. Sunrise and sunset are governed by two major factors, the seasons (caused by the tilt of the Earth relative to the sun) and the ellipticity of the Earth's orbit that causes the actual time of mid-day (highest point of the sun in the sky) to vary by - 16 minutes in November to +14 minutes in February.

Up at European latitudes, the effect of the seasons (many hours) greatly outweighs the ellipticity (+/- 15 minutes), however, as we move towards the tropics, the effect of the seasons is diminished and the ellipticity becomes dominant.

For sure, the longest day is the Summer Solstice on or around the 21st June, and the shortest day the Winter Solstice on 21st December, however, in December, mid-day is retarded by the elliptical component thus moving the 'earliest sunset' backwards in date and the 'latest sunrise' forward, the amount depending on your latitude.

In London, for example, the ellipticity still has a small effect and the earliest evening is 9th December and the darkest morning, 29th December. The weather is normally so foul that most people wouldn't observe the subtlety, but in the tropics, it is more obvious.

The bottom line is that during October, November and early December, the evenings are a bit shorter than normal.

As an interesting note, Frederick Forsyth in his book 'Day of the Jackal', attributes the failed assination attempt of President de Gaulle to the assassin using the sunset tables from the wrong year. This is incorrect, it doesn't change (not in our life span). He was thinking of tides I suspect.

Monsoons and Rain:   What is a monsoon? When is the rainy season?

An impressive waterspout off Jerudong, August 2002 (right) and a classic picture (left) from the West Pelaut in 2007.

The term ‘monsoon’ comes from the Arabic word ‘mausim’ meaning season. The popular misconception, associated with Hollywood films of torrential rains in India, is that a monsoon is a wet season. This is not so, it is purely a wind direction that may (in the case of India), or may not, bring rain.

Brunei famously has two seasons:- the wet season and the very wet season! In Winter, China is seriously cold and Australia very hot. The denser, colder air flows from China towards the south and, being deflected by the earth’s rotation, crosses Borneo from the north-east. This is the north-east monsoon. It starts after the autumnal equinox as China cools down and is normally established by November. It is characterised by a steady force 4 north-early wind that, in its early stages, relaxes at night and allows the moist jungle air to flow out to sea causing heavy rain. By February the winds are stronger and the nightly ‘back-flow’ ceases, causing a marked decline in rainfall.

The surf pounds on the beach and can be heard throughout Panaga. Around the vernal equinox, the winds abate as China warms up. The air flow now reverses and from June to August the wind blows from the south-west. Australia never gets as cold as China so the south-westerly monsoon is weaker. Additionally in Brunei, the wind blows offshore and so the real effect of the wind is not noticed close to the beach.

Towards the end of the SW monsoon, the typhoon season starts in the west Pacific. Sabah is famously called ‘the Land below the Wind’ meaning that it lies south of the typhoon belt. However, the effect of the typhoons is felt as they drag huge quantities of air from the South China Sea. This spins off numerous squalls and can really chop up the sea in August and September. Waterspouts are not uncommon during this season but rarely come ashore to cause significant damage (Bakam 1979, Panaga 1993 - below. The impressive monsters above, like the vast majority of waterspouts, never come ashore.)

The statistics below show that February / March are the driest months, receiving on average a quarter of London's annual rainfall each month. Thereafter the months get progressively wetter up to December / January during which months the rainfall doubles. In January 1963, twice London's average annual rainfall descended. These statistics are long-term, and the graph below reveals that February has been particularly dry for the last four years, and December rather wet for the last two. 2007 may yet be a record year since 102 inches (out of an annual average of 112) has fallen in the first seven months of the year.

Sea Temperature   Is it always like a bath?

Not quite! The monsoon explains it all. The South China Sea is mainly enclosed and, apart from the Palawan Trench just 40 miles off the coast where the ocean drops to over 3,000 metres deep, the Sea is relatively shallow with numerous reefs and shoals. The sea can, therefore maintain a constant, tropical temperature of 30 C for most of the year. Only when the northeast winds kick in around late November does the south-westerly motion of the sea pick up the colder water from the offshore trench and the sea drops quickly to 26 C, a temperature that is maintained until the change of monsoon in April / May. A by product of the NE winds is for every piece of rubbish, ranging from massive timber to a million plastic bottles, to get washed up on the Panaga Beach. The chart below is a practical plot of the sea temperature, being taken from the author's dive records in Borneo (yellow) and specifically Brunei (red).

Temperature  Where’s the land temperature chart?

To be honest there’s not much to say here! The absence of a temperature chart might seem an omission, but the range of temperature fluctuation is very small. The average maximum in January (the coldest month) is 30 C. By April / May (the hottest months) the maximum is averaging 32 C, after which it slowly decreases for the rest of the year. The average minimum temperature is always 23 C. The temperature virtually never exceeds 35 C.

Winds, Waves and Current

The monsoon seasons are described above, however, it is the severity of the winds and the response of the waves, both to the local winds and the more distant seasonal effects, that concerns us here. The sea, in turn, responds as a body in theory, but in practice, the various layers of water that make up offshore Brunei, all respond in different ways.

We'll start with the Beaufort Wind Scale, originally devised by British Rear-Admiral, Sir Francis Beaufort (1774-1857) in 1805. The table below is taken from the original, but with modifications for our own boat, a typical Borneo dive vessel, the ‘Naga Laut’. I've had to delete the charming column on ships, where, for example, a force 6, called, in typical English understatement 'a Strong Breeze', is described as "Man-of-war will have single reefed topsails and top-gallant sails." At Force 7, even the English have admitted that it might be a 'Near Gale', and that the "Man-of-war will have double-reefed topsails, jib and courses." Great stuff, and I'm sure members of the club's sailing section fantasise about this sort of thing as they feel at one with the ghosts of Sir Francis’s Drake, Beaufort and Chichester.

I've taken the liberty of splitting up forces 3 and 4, since that is where local Borneo conditions change from 'everybody happy' to 'total discomfort’ and the unpleasant prospect of a long, tedious and wet journey home.

As regards currents, they can be summed up in one word 'unpredictable'. There are statistics available, however, on a day by day basis currents vary both laterally and with depth. In the SW monsoon, the current can run to the NE at Fairley and to the SW at Ampa as a giant clockwise eddy is formed by the ocean passing the Baram Point. The sea is often covered by fresher river water and this obeys its own laws, usually being moved by a combination of wind and the driving force of the river. It's not unusual to find that the surface waters have distinct visibility, current, salinity and temperature from the underlying water. Roughly speaking, the near surface waters move away from the monsoon wind direction. This is strongly observed on the mouths of the local rivers (Panaga, Seria, Bera, Anduan, Anduki, Liang, Kayu Ara and Tali) where the entry to the sea can move by as much as 200 metres between the seasons.

Record Weather

A nasty August squall off the Potteries Beach, Lutong (1979)

January / February 2007

The year 2007 saw the fifth wettest January and the second wettest February in the last half century. This is well beyond the standard deviation from average and thus can be called really wet. However, this has happened before. If you consider three month periods, the last really wet spell was the winter of 1995/1996 (10% wetter than now) or 1962 /1963, a massive 40% wetter. In January 1963, 49.7 inches of rain fell compared to 28.3 inches in January 2007. In January 1981, 33 inches fell, but 30 of those fell in four days as I mentioned above!

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