Finally, after a lengthy delay, the atmosphere has responded to the change in increased water temperatures across the Pacific Ocean and has now entered an El Niño phase.
Specifically the 90-day Southern Oscillation Index is below the threshold of -7, a westerly wind anomaly has developed over the western Pacific, and a reduction in convection has been observed around Indonesia and southeast Asia.
In the Indian Ocean a firm positive Indian Ocean Dipole pattern has emerged. This is the Indian Ocean version of El Niño but with a less sexy name. Like El Niño, it also dries out and warms up Australia during winter and spring and when combined with El Niño can enhance the drying and warming in some regions.
It’s important to realise that an El Niño and positive Indian Ocean Dipole double does not guarantee a hot, dry spring. The last one in 2015 did not create widespread drought — apart from in pockets of southern Australia and eastern Queensland.
A misconception among Australians is that El Niño leads to a dry summer. This is incorrect. The main impact is winter and spring, although summer temperatures are still normally on the warmer side.
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