Rain has reached most districts in NSW this week and large areas of the state could be in for an unusually wet start to winter as well.
A tropical air mass being dragged south from QLD is delivering a decent burst of late-autumn rain across NSW this week.
This rain ramped up on Wednesday and moderate to heavy falls are likely to continue in some parts of the state on Thursday and Friday. Showers should ease over NSW on the weekend as the wet weather pattern starts to break down.
This latest round of rain in NSW is being enhanced by a lingering La Nina pattern in the Pacific Ocean, which has remained unusually well-established throughout autumn and could linger into June.
New data released by the U.S. Climate Prediction Centre (CPC) this week shows that La Nina is persisting in the Pacific Ocean at a strength not seen during May for more than two decades.
According to Bureau of Meteorology's latest Climate Driver Update, "La Nina remains active in the tropical Pacific Ocean. While having shown signs of a slow decline over recent months, in the past fortnight this decline has stalled, and some indicators have strengthened again. Autumn is the usual time of the year in which ENSO events decay and return to neutral."
On the other side of Australia, there is good agreement between long range forecast models that a negative Indian Ocean Dipole will develop this winter and persist until at least mid-spring. La Nina and a negative IOD both increase the likelihood of above-average rain in NSW, particularly on and west of the ranges.
With two wet-phase climate drivers likely to be influencing Australia's weather patterns in May and June, NSW can expect to see more wet in the weeks ahead.
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