Recent cooling below the surface of the Pacific Ocean may diminish the shelf life of the El Nino event that has plunged parts of Australia into drought.
The Bureau of Meteorology says the El Nino, a warming of sea surface temperatures in the central and eastern tropical Pacific that tends to bring drier weather to Australia, remains strong and is near its peak.
But some below-surface cooling has occurred in the eastern tropical Pacific over the past fortnight, the BOM’s latest El Nino Southern Oscillation Wrap Up says.
‘Changes in the sub-surface are an important indicator, as the sub-surface plays a significant role in maintaining the strength and longevity of El Nino events,’ the report said on Tuesday.
The below-surface ocean temperatures are still significantly warmer than average.
This year’s El Nino event is one of the strongest on record, matching the strength of record El Ninos in 1997/98 and 1982/83.
Both of those events brought severe droughts to eastern Australia, and the 1982/83 drought was a major factor in the Ash Wednesday bushfires that killed 71 people in Victoria and South Australia on February 16, 1983.
The influence of El Ninos varies at this time of year, depending on how quickly they begin to break down, but most deliver below-average rainfall and a continuing drying influence on southeastern Australia but more rain in inland Western Australia.
Models suggest the event will start to decline in 2016, but the tropical Pacific is unlikely to return to neutral until at least autumn.
Meanwhile, a warming of Indian Ocean sea surface temperatures known as the Indian Ocean Dipole may provide extra moisture for rain systems across Australia.