Issue Notes

ENSO status: Neutral (El Nino Alert)

Sea surface temperatures (SSTs) warmed up ever so slightly in March, placing the Nino3.4 Index well into El Nino thresholds. Based on this, the North American Weather services have issued an El Nino advisory, effectively declaring it an El Nino albeit weak. Due to the higher thresholds used by BoM, the Bureau maintains an alert.

The Nino3.4 index reached a peak of 0.9 during the week starting on the 24th of March and has lingered at 0.8 since then. On the other hand, the Southern Oscillation Index (SOI) recorded a value of -6.8 in March, the second month in a row with values into the El Nino territory.

Current consensus suggests weak El Nino conditions will continue through autumn and winter, with six out of eight international models maintaining El Nino thresholds through to at least August with a 60-70 % chance of an El Nino event lasting through winter.

Due to the recent Tropical Cyclone activity off northern WA, SSTs have cooled down significantly along Australia's western seaboard but remain warmer than average along the eastern seaboard.

The climate outlook favours average-to-below average rainfall across Qld, NSW and Vic through the southern hemisphere autumn (in particular the first half) and again towards the second half of winter. There are some early indications a Positive IOD could establish itself in the Indian Ocean later in winter with four out of six international models hinting so. During Positive IODs, central and southeastern Australia tends to see a reduction in rainfall amounts towards the second half of winter and early spring.

With warmer than average SSTs across the Tasman Sea, extreme weather events such as East Coast Lows (ECLs) can still bring intense periods of rainfall east of the Great Dividing Range leading to flash floods. May to July are the peak months for ECLs.