Climate Driver Update history
Climate drivers in the Pacific, Indian and Southern oceans and the Tropics

Sea surface temperatures (SSTs) in the central tropical Pacific Ocean are within the ENSO-neutral range. The pattern of SST anomalies in the equatorial Pacific remains similar to two weeks ago. To the north and northwest of Australia warm anomalies strengthened compared to two weeks ago. Warm SST anomalies also persist over much of the far western Pacific and across South East Asia and north across the East China Sea.

The El Niño–Southern Oscillation (ENSO) in the tropical Pacific Ocean remains neutral (neither El Niño nor La Niña). Although some very weak La Niña-like patterns continue (such as cooler than normal ocean temperatures and reduced cloudiness in the central and eastern Pacific), La Niña thresholds have not been met. Climate models and current observations suggest these patterns will not persist. The likelihood of La Niña developing in the coming months is now low, and hence the Bureau’s ENSO Outlook has shifted from La Niña WATCH to INACTIVE.

The Indian Ocean Dipole (IOD) also remains neutral (neither positive nor negative), as is typical at this time of year. When ENSO and the IOD are neutral they have limited impact on Australian climate.

The climate of Australia, and other countries around the tropical Indian Ocean and western Pacific Ocean, has been strongly influenced during the second half of 2016 by both a strong negative IOD in the tropical Indian Ocean (that ended in November) and the weak La Niña-like pattern in the tropical Pacific (which has eased). This combination of climate drivers contributed to Australia observing its wettest May to September on record in 2016.

Cloudiness near the Date Line is below average, and has been generally below average since the start of August.

Equatorial cloudiness near the Date Line typically increases during El Niño (below average OLR) and decreases during La Niña (above average OLR).

For the 5 days ending 4 December trade winds were near average strength across the eastern tropical Pacific Ocean, but weaker than average just on and east of the Date Line, while stronger than average in the remainder of the western tropical Pacific Ocean.

During La Niña events, there is a sustained strengthening of the trade winds across much of the tropical Pacific, while during El Niño events there is a sustained weakening, or even reversal, of the trade winds.

Outlooks from the eight international climate models surveyed by the Bureau continue to indicate that neutral ENSO conditions are the most likely outcome for the southern hemisphere summer. One model continues to indicate the likelihood of a brief, late-starting La Niña over the summer. Other models generally indicate neutral conditions for the central Pacific.

A La Niña forming so late in the year has only occurred once since 1980, with the 2008–09 La Niña declared in December 2008.

All models indicate warming of the central Pacific is likely over the coming months.

Weak cool SST anomalies were present in a thin band along much of the central to eastern equatorial Pacific during November. Warm anomalies were present in the far western Pacific, across most of the southern Pacific outside of the tropics, and across waters around Australia, Indonesia and most of eastern Asia. Large areas adjacent to southeast Australia and between Australia and Indonesia were more than 1 °C warmer than average, although covering a smaller area than in October.

The November value for the NINO3 and NINO3.4 regions were both −0.3 °C, while the value for NINO4 was −0.2 °C. 

The 30-day Southern Oscillation Index (SOI) to 4 December is −1.2; within the neutral ENSO range. SOI values have been within the neutral range since mid-October.

Sustained positive values of the SOI above +7 typically indicate La Niña while sustained negative values below −7 typically indicate El Niño. Values between about +7 and −7 generally indicate neutral conditions.

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 4 December was −0.02 °C.

The influence of the IOD on Australian climate is weak during the months of December to April. This is because the monsoon trough shifts south over the tropical Indian Ocean changing wind patterns, which prevents an IOD pattern from being able to form.

However, the continued presence of much warmer than average water to the north and northwest of Australia may see continued influence on Australia, including enhanced rainfall.

The four-month sequence of sub-surface temperature anomalies (to November) shows cooler than average water across the sub-surface of the central to eastern equatorial Pacific Ocean. Compared to October, cool sub-surface anomalies west of the Date Line have weakened and were close to average. Weak warm anomalies persisted in the top 100 m of water west of 160° E; this region has been slightly warmer than average in each month since July.

The sub-surface temperature map for the 5 days ending 4 December shows temperatures close to average across the sub-surface of the equatorial Pacific.