MELBOURNE, Australia – The El Niño–Southern Oscillation (ENSO) is neutral—neither El Niño nor La Niña. Models indicate the tropical Pacific is very likely to remain ENSO-neutral for the remainder of 2019, reports Australian Government Bureau of Meteorology in its latest report. With ENSO playing less of a role, a positive Indian Ocean Dipole (IOD) is likely to be the dominant climate driver for Australia’s weather for the coming months.
Central to eastern tropical Pacific sea surface temperatures are slightly above average, while sub-surface temperatures are close to average. Atmospheric indicators of ENSO have shown some variation, but the recent drop in the Southern Oscillation Index (SOI) is related to short-term variability in tropical weather patterns rather than a shift back towards El Niño. Cloudiness near the Date Line and trade winds remain close to average.
All climate models surveyed by the Bureau indicate the tropical Pacific will remain ENSO-neutral through the southern hemisphere winter and spring.
Indian Ocean Dipole (IOD) index values have been near the threshold for a positive IOD in recent weeks. The broad pattern across the Indian Ocean has remained positive IOD-like, with warmer than average sea surface temperatures near Africa and cooler than average waters to Australia’s northwest. The latest week has seen the index again above the positive IOD threshold.
Most climate models surveyed forecast positive IOD conditions for the remainder of the southern hemisphere winter and spring. Typically, a positive IOD brings below average winter–spring rainfall and snow depths, above average temperatures, and an earlier start to the fire season for southern and central Australia.