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Enso is neutral, but there is 50 percent chance of spring El Niño, says Bom

La Niña

According to the Australian Government Bureau of Meteorology (BOM), the El Niño – Southern Oscillation (ENSO) remains neutral. However, climate model outlooks and recent warming in the tropical Pacific Ocean mean there is a greater than usual chance of El Niño forming later this year.

The Bureau’s ENSO Outlook is currently at El Niño WATCH, which means the likelihood of El Niño forming in 2018 is approximately 50%; double the normal chance.

Some ENSO indicators show signs of El Niño development. Sea surface temperatures in the central to eastern tropical Pacific Ocean remain neutral, but have been slowly warming since April.

Waters beneath the surface are also warmer than average; a common precursor of El Niño. In the atmosphere, indicators such as the trade winds and Southern Oscillation Index (SOI) are neutral but show El Niño-like traits.

That is, there are weaker than average trade winds in parts of the central Pacific, and the SOI is negative.

Most international climate models surveyed by the Bureau suggest more warming is likely for tropical Pacific sea surface temperatures. Five of eight models indicate this warming will reach El Niño levels in the southern hemisphere spring, while a sixth model falls just short.

During El Niño, rainfall in eastern Australian is typically below average during spring and daytime temperatures are also typically warmer than average for southern Australia. A neutral ENSO phase has little effect on Australian climate.

The Indian Ocean Dipole (IOD) remains neutral. Most climate models suggest the IOD is likely to remain neutral in the coming months.