The Bureau of Meteorology has issued an El Nino Alert, indicating a higher chance of the type of drier weather and warmer temperatures associated with increased bushfire risk in south eastern Australia.

El Nino impacts can include increased risk of extreme heat, increased bushfire danger, a later start to the northern wet season and reduced tropical cyclone numbers.

Senior Climatologist Catherine Ganter says models show it’s very likely tropical Pacific Ocean temperatures will reach El Nino levels during winter and some movement in the atmosphere towards El Nino conditions has also been seen.

“While our El Nino Alert criteria have been met, these changes will need to strengthen and sustain themselves over a longer period for us to consider an El Nino event,” she said today.

An Alert indicates a 70% chance of an El Nino developing this year, which equates to roughly three times the normal chance. Previously the bureau had issued an El Nino Watch, indicating a 50% chance.

The events, which typically suppress rainfall in eastern Australia during the winter and spring months, describe changes in the tropical Pacific Ocean that affect global weather. They occur on average every 3-5 years.

The Bureau of Meteorology’s latest long-range forecast for up to three months ahead, released last week, already points to an increased chance of below-average winter rainfall for almost all of Australia. The Alert doesn’t change that outlook.

A climate driver update today also says the Indian Ocean Dipole (IOD) remains in a neutral phase, but all models suggest positive IOD event thresholds may be reached in winter.

A positive IOD typically suppresses winter and spring rainfall over much of Australia, and if it coincides with an El Nino, it can exacerbate drying effect. But long-range IOD forecasts made at this time of year have generally had low accuracy and should be viewed with caution beyond June, the bureau says.

El Nino events typically begin to develop during autumn, strengthen in winter/spring, then decay during summer and autumn of the following year.

The climate driver has shifted toward warmer and drier conditions after three consecutive La Nina events, which have been associated with the record flooding in eastern Australia.