THE possible development of an El Niño event in winter has increased in recent weeks as water temperatures in the eastern tropical Pacific have continued to increase.
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The pattern is still a neutral one but waters below the surface of the tropical Pacific have warmed and further warming is expected in the next month or so.
This warming is usually increased by the development of an El Niño.
It is some years since we have been in an El Niño pastern so it was inevitable that one would come along shortly - this is all part of the natural climatic cycle.
The onset of El Niño conditions in winter initially does not have a great effect on NSW rainfall but persistence into spring and summer usually indicated below average rainfall.
However, this has not always been the case.
Some El Niño events in the past have had little effect on NSW rainfall but are more likely to affect Queensland rainfall and temperatures.
The development on an El Niño which persisted until the end of the year would definitely indicate above average temperatures across the State next spring and summer - possibly even warmer than the past two summers.
In the meantime, a neutral pattern will persist bringing the occasional rain event.
Many parts of NSW have had useful falls recently and this is likely to persist for much of autumn with the Indian Ocean Dipole (IOD) likely to remain neutral as well.
Temperatures will return close to normal for a while in the second half of the season and moving into winter, increased variability in temperatures is favoured while rainfall will become lighter but more uniform as thunderstorms decrease in importance.
Variability in temperature could result in the occasional early season cold spell (which brief periods of significantly below normal temperatures) but mainly in May.
Contact Don White, Weatherwatch, (02) 9451 7102 or fax (02) 9975 1608.
