The Bureau of Meteorology’s long-term winter forecast has seen a swing towards wetter conditions in north-eastern Australia, but Western Australia’s cropping belt could be facing markedly drier conditions.
South-eastern Australia remains hard to predict, but BOM meteorologist Lyn Bettio there was a slight swing towards a wetter season since last month’s update, but that it was still firmly in neutral territory.
"We don’t like to read too much into these small swings as it still very hard to tell," Ms Bettio said.
The pattern of seasonal rainfall odds across Australia is a result of higher than average temperatures in the Indian Ocean, generally responsible for greater rainfall, and cooler than average waters in the central to western equatorial Pacific in association with the decaying La Niña pattern.
The chances of exceeding the median rainfall over winter are between 60 and 70 per cent over much of Queensland, and northeastern parts of NSW, meaning for every ten years with ocean patterns like the current, about six or seven winter periods are expected to be wetter than average in these parts of northeastern Australia.
The news will be welcome for winter croppers in northern NSW and southern Queensland, who have good subsoil moisture due to heavy summer rain, but are waiting for planting rains.
For south-east Australia, there has been a mild swing towards a wetter winter – with the Bureau increasing the changes of above average rainfall by five percent on its April figures – however it remains neutral at 50-55pc of a wetter than average winter for virtually al of Victoria and southern NSW.
In the west, farmers will be glad of their good start through April and May – as Ms Bettio suggested there is only a 30-40pc chance of above average rainfall over the cropping belt.
The accuracy of the forecast varies from region to region. Ms Bettio said the models are reasonably accurate as a predictive tool over much of south-eastern Australia, but are not so effective in WA, particular in the south-west of the state.
The major factors in the Bureau coming to its forecast are the declining La Nina event in the Pacific Ocean and warming of the Indian Ocean off the coast of Western Australia.
Ms Bettio said the signals were especially strong in north-east Australia.
"It’s hard to interpret as the ocean temperatures can influence different parts of the country according to the time of year. At present the warming of the Indian Ocean is having a large affect on readings in north-east Australia."
The Pacific Ocean is largely back to neutral conditions – with the Southern Oscillation Index (SOI) at zero for the past 30 days – however there is no immediate threat of a return to an El Nino pattern – associated with dry conditions across eastern Australia.
All the BOM’s models predict neutral conditions in the Pacific over the coming three months.
The importance of the SOI will be noted by many in the farming community along the east coast. It dropped rapidly last July – which many believe caused the poor early spring rainfall, in spite of a La Nina pattern re-establishing itself later in the year.
The grain market has not reacted to the positive outlook for the northern grainbelt.
ABB new season wheat prices rose $4 a tonne on Tuesday to $334/t port in Victoria.
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