El Nino's grip expected to tighten through to early next year at least

The Bureau of Meteorology last month declared the El Nino had officially arrived but it is less clear how long it will stay.

"Climate models indicate this El Nino is likely to persist until at least the end of February," BOM said.

This means warmer than average conditions are likely across most of Australia from November to January and below median rainfall expected for much of western, northern and southern Australia.

El Nino occurs on average every two to seven years, and typically last nine to 12 months.

But some of those climate models relied on by BOM show El Nino conditions expected to ease after February.

For instance, the Meteorological Service of Canada says El Nino conditions in the central-eastern equatorial Pacific have strengthened further.

"Key oceanic and atmospheric variables are consistent with a moderate El Nino event," the agency says.

The Canadian forecast is for neutral conditions "becoming the most likely in May-July next year with a 57 per cent chance".

Other overseas climate models expect similar.

During an El Nino, sea surface temperatures in a central region of the equatorial Pacific become warmer than average, resulting in a shift in atmospheric circulation.

BOM says the climate modelling it relies on for its long range forecasts indicate "further warming of the central to eastern Pacific is likely".

The bureau says there is reduced chance of tropical cyclone activity across the north this wet season and a delay in the arrival of the monsoon.

The El Nino and positive Indian Ocean Dipole and recent conditions indicate an increased risk of heatwaves and bushfires this year.

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