Hold onto your ski helmets, people, we’re in for a bumpy ride as the Bureau of Meteorology (BOM) move from an El Niño WATCH to El Niño ALERT.

Say what? Yes this means that there is around a 70% chance of an El Niño developing this year.

But what does that mean, exactly? In Australia changes during El Niño could include reduced rainfall for eastern Australia (ouch), warmer daytime temperatures for the southern two-third of Australia, increased risk of extreme heat, increased bushfire danger in south-eastern Australia and increased frost risk linked to clear skies at night.

It also means decreased alpine snow depths and a later start to the northern wet season.

Bureau of Meteorology Senior Climatologist Catherine Ganter said climate models and indicators now meet the Bureau’s El Niño ALERT criteria.

“While the models show it’s very likely the tropical Pacific Ocean temperatures will reach El Niño levels during winter, we have seen some movement in the atmosphere towards El Niño conditions,” Ms Ganter said.

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

The Bureau’s criteria for the definition of El Niño ALERT have been developed as part of a staged system to alert Australians on the increased likelihood of El Niño.

El Niño describes changes in the tropical Pacific Ocean that affect global weather and it occurs on average every 3 to 5 years.

During El Niño, there is a higher chance of drier weather in eastern Australia and it’s more likely to be warmer than usual for the southern two-thirds of Australia.

“The Bureau’s long-range winter forecast is for drier and warmer conditions across almost all of Australia and the climate conditions in the Pacific Ocean are already factored into our forecasts,” Ms Ganter said.

“The long-range forecast for winter also shows an increased chance of below average rainfall for almost all of Australia and the move to El Niño ALERT does not change this forecast.

“The Bureau currently forecasts Australia’s rainfall and temperature up to 3 months ahead. We use a climate version of our weather model to make these long-range forecasts and this model uses information about ocean and land temperatures, wind patterns and more.

“This model already takes into account the likely conditions in the Pacific Ocean, but also conditions elsewhere across the globe, such as the tropical Indian Ocean and how they are also likely to influence Australian weather and climate,” Ms Ganter said.

El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), where the climate is often drier than usual in eastern Australia during winter and spring.

ENSO describes a naturally occurring cycle in the climate system, including the location of warmer or cooler than average sea surface temperatures in the central and eastern tropical Pacific Ocean, and its connection with the trade winds and patterns in the atmosphere.

Ms Ganter said even if an El Niño develops, its impact can vary depending on where you are, as well as from event to event.

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