Bureau of Meteorology/Australia Strengthens El Nino Outlook
Discussion: The Bureau’s ENSO Outlook has been raised to El Niño ALERT. This means there is approximately a 70% chance of El Niño occurring in 2018—around triple the normal likelihood. Similarly, in the Indian Ocean, a positive Indian Ocean Dipole (IOD) may have started.
When combined, these two events in spring increase the possibility of a dry and warm end to the year across Australia. It also raises the risk of heatwaves and bushfire weather in the south, but reduces the risk of tropical cyclone activity in the north.
The tropical Pacific Ocean has warmed in recent weeks due to weakening of the trade winds, while the Southern Oscillation Index (SOI) has fallen to typical El Niño levels. Models suggest further warming of the Pacific is likely. Four of eight models predict El Niño thresholds will likely be exceeded in the coming months, with another two falling just short.
In the Indian Ocean, there are signs that a positive IOD is currently underway. The IOD index has exceeded the threshold (+0.4 °C) for the last four weeks. However, these values must persist until November for it to be considered a positive IOD event. Model outlooks suggest positive IOD values are likely to continue through the austral spring, before returning to neutral values in late November to December.
Climate Impact: A Modoki-style El Nino is ahead for late 2018/early 2019 followed by a conventional and possibly strong El Nino for at least the first half of 2019.
Fig. 1: Bureau of Meteorology/Australia has increased the intensity of their El Nino forecast for late 2018 and quarter 1 of 2019.
Fig. 2: Subsurface water temperature anomalies across the equatorial Pacific Ocean indicate plenty of fuel for El Nino ahead.