We’re especially mindful of our colleagues in Australia who live with extremes of drought and floods, as well as having to put up with more flies than the rest of the world together, but at the same time, we should take our hats off to these fellows who do such an admirable job against the odds, and must rank in their dealings with these adversities, as some of the best farmers anywhere.
You’ll understand our elation then, at the recent announcement by the international scientific community that El Nino is now in rapid retreat, which means we can start looking forward to a “flip-flop” in our climatic fortunes. While visitors to Summerhill would never know that for the best part of two years we’ve been existing in some of the driest conditions in almost forty years, other than looking at our dam levels (and even there, they’re not so bad), they’d also be mesmerized at the rude health of our winter pastures. Truth is, we got lucky again with some excellent moisture in February and some “just-in-time” rain in each of the subsequent months, just as we have in every one of the years we’ve been here.
According to Rob McElwee, during the past month, the abnormally warm waters along the Eastern equatorial Pacific that typify an El Nino event, have disappeared. In fact, the more normal condition of the colder sub-surface waters welling up to the surface has returned. It is this up-welling that creates the good fishing grounds off the Chilean coast and it is the disappearance of fish that has historically been the first indicator of a developing El Nino.
El Nino-Southern Oscillation
El Nino is one extreme end of what is known as the Southern Oscillation. Warm surface water sloshes in slow motion from the western Pacific to the eastern Pacific during the El Nino phase, then it sloshes back again in slow motion to create La Nina.
The development of either of these phenomena is slow and irregular which means that there are long, “normal”, periods.
But, after a major El Nino, such as the 2015-16 one, it is not surprising to see a swing through neutral to La Nina. Historically, La Nina has followed several strong El Nino events, including the 1997-98 event, possibly the strongest one on record.
Chance of La Nina?
Most computer models have predicted the end of El Nino and a brief period of neutral El Nino -Southern Oscillation conditions by the end of May. From then on, there is increasing uncertainty as to the timing and strength of any La Nina phenomenon.
Overall, La Nina is favoured to develop during the Northern Hemisphere summer of 2016, with about a 75 percent chance of La Nina during the Autumn and Winter of 2016-17.
Effects of La Nina
La Nina can be as disruptive to the world's weather as its opposite number. The known effects are sometimes opposite, for example, rainfall is enhanced over Indonesia, Malaysia and Northern Australia. Wetter than normal conditions are also observed over Southeastern Africa and Northern Brazil during the Northern winter season.
During the Northern summer season, the Indian Monsoon rainfall tends to be greater than normal, especially in Northwest India.
More rain during the Indian Monsoon season and more rain over Indonesia, Malaysia and the Philippines, let alone Northern Australia could be seen as good news.
Given the shortage of recent rains and heatwaves enhancing evaporation, drought has become common and a good dose of wet weather would go some way to reducing it.