The powerful El Nino in the Pacific is continuing to strengthen but the worst impacts for Australia may be tempered by record warm waters in the Indian Ocean, the Bureau of Meteorology said.
Temperatures in the central tropical Pacific are now 2.4 degrees above normal, a level that is comparable to the same stage of the record 1997-98 and 1982-83 El Ninos, the bureau said in its fortnightly update on Tuesday. The record anomaly is 2.8 degrees in 1997-98.
The El Nino event is "still going strong but we're expecting things to slow down over the next couple of months," Andrew Watkins, manager of the bureau's climate prediction services, said.
An ensemble of climate models compiled by the bureau (see below) points to a peak late this year, with El Nino-like warmth persisting until May. Other scientists last week suggested the event may be prolonged.
Farmers and firefighters are among those watching the skies closely - both in Australia where a record hot October has brought forward the bushfire threat in southern states and also in Indonesia, Papua New Guinea where severe droughts have hit crops and fanned forest fires.
Historically, the worst El Nino impacts have come when temperatures in the Indian Ocean have been relatively cool off north-western Australia compared with the western Indian Ocean - such as the current conditions.
However, what's moderating the otherwise potent brew is the fact that the Indian Ocean south of the Equator is at record levels of warmth (see chart below), with heat anomalies in October the largest for any month on record, Dr Watkins said.
"They are all competing with each other," he said. "It's been a very unusual year in many ways, with just enough rain around to tease us."
The changed wind patterns that signal an El Nino mean the Pacific Ocean absorbs less heat than usual from the atmosphere. The UK Met Office said on Monday that the extra kick along - added to background climate change - has lifted global warming to more than 1 degree above pre-industrial levels for the first time.
With both the Indian and Pacific Oceans so warm, odds continue to favour 2015 as likely to easily exceed the record annual global temperatures set just last year, meteorologists say.
The current El Nino has been fed by eight bursts of westerly winds that have helped push warm waters close to the surface in the key central Pacific zone, as shown in the bureau's chart of temperature anomalies:
The Indian Ocean feed of moisture that brought 50mm of rain over the past week to parched areas of inland Australia such as western Victoria will only go part of the way to make up rainfall shortfalls over the past year or more, Dr Watkins said.
The bureau on Tuesday updated its seasonal forecast for streamflows for November to January and predicted below-average flows in 102 sites and above-average readings in just two.
With soil moisture levels so low, it will take several good rain events to create much run-off to fill dams and reservoirs in many regions, Dr Watkins said.