THE emergence of a climatic event that can be categorised as El Nino remains as elusive as it was a month ago, but El Nino-like conditions look more likely than not to plague eastern and northern Australia through summer.
The Bureau of Meterology's latest ENSO update again gives 50 per cent odds of an El Nino emerging over the next few months - meaning double the normal likelihood - but that only tells part of the story.
"An El Nino doesn't have to be locked in for us to see El Nino-like effects,” said Andrew Watkins, BoM’s manager of Climate Prediction Services.
Since May, Australia’s east and north have been drier than normal, outside some unusually wet pockets like the Sydney area. It's basically been El Nino weather, Dr Watkins said, although the criteria climatalogists use to declare the event remain absent.
"It seems to be toying with us," he said. "The Southern Oscillation Index has been staying below minus eight for 2-3 months now, something you would more typically expect to see if an El Nino was in place, but ocean temperatures, trade winds, clouds, are not yet at the threshold level where we can say we've entered an El Nino."
Six of the eight climate models that BoM interrogates point to an El Nino emerging over the next few months, but looking at the stalemate in the Pacific, Dr Watkinds said, "I think it's going to keep teasing us for some time".
If a distinct El Nino pattern does emerge, it locks in the likelihood of drier warmer weather at least until February.
Another frequent impact of El Nino is to delay the onset of the monsoon, a prospect welcomed by no-one, and definitely no-one in inland Queensland.
Dr Watkins suggests that graziers be cautious in their response to one-off rainfall events until it's apparent that the dry pattern is breaking up. “It’s a time to be careful about managing risk,” he said. "There's no reason to be assuming lots of rain over eastern and northern parts of Australia over the next few months."
Sporadic rainfall is flukey enough, but the seasonal outlook points to warmer than usual temperatures over much of the agricultural zone affected by rainfall deficits.
Heat sucks away soil moisture - and in the absence of soil moisture, air isn't cooled by envirotranspiration, so air temperatures are raised more, diminishing the benefit of any rain that falls.
Bom’s September-November seasonal outlook suggests southern Australia and inland Queensland are likelier to experience warmer days than normal over coming weeks.
Areas of the south-east mainland may have drier than normal conditions, with the prospect of normal rainfall over the rest of the country about 50/50.
Matthew Cawood
National writer for Fairfax Agricultural Media.
National writer for Fairfax Agricultural Media.
