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

For the week ending 18 June, sea surface temperatures (SSTs) were slightly warmer than average across most of the equatorial Pacific Ocean. Generally weak warm anomalies are also present across much of the South Pacific, including areas immediately south of the equator.

The NINO3.4 SST anomaly has remained at around +0.5 °C since mid-April, while NINO3 dropped further to +0.3 °C in the last fornight. In contrast NINO4 warmed 0.1 °C to +0.5 °C.

The Bureau's ENSO Outlook has been reset to INACTIVE after an easing of climate model outlooks, and a reversal of the early autumn warming in the eastern tropical Pacific Ocean.

In the atmosphere, the trade winds and Southern Oscillation Index are well within the neutral range. Equatorial sea surface temperatures in the central Pacific are slightly warmer than average. However, far eastern Pacific Ocean sea surface temperatures, which were several degrees above normal near the Peruvian coast during March and April, cooled during May and June. This warmth had the potential to spread and develop into an El Niño event with global effects, but eased as trade winds failed to reinforce the ocean warmth. Other ENSO indicators also remain neutral.

All eight international models surveyed by the Bureau of Meteorology now suggest tropical Pacific Ocean temperatures are likely to remain ENSO-neutral for the second half of 2017. This compares to seven of eight models that suggested a possible El Niño in April.

While models have steadily eased back the likelihood of El Niño, most still indicate an increased chance of warmer and drier than average conditions for Australia over winter.

The Indian Ocean Dipole (IOD) is neutral. Three out of six climate models suggest a positive IOD will develop by the end of winter, and three are neutral. A positive IOD is typically associated with a drier than average winter and spring for southern and central Australia.

Cloudiness near the Date Line is slightly below average. Cloudiness has been fluctuating around average for the past two months, though has tended towards less cloud than average overall.

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

Trade winds for the 5 days ending 18 June were near average over the tropical Pacific.

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.

All eight international climate models surveyed by the Bureau indicate that ENSO-neutral conditions are likely for the second half of 2017, having progressively eased back from seven of eight models forecasting El Niño back in April.

However, while the likelihood of El Niño developing in the coming months is low, climate outlooks for winter suggest widespread drier than average conditions across southern and central Australia, combined with warmer than average days.

SST anomalies for May show sea surface temperatures in the western half of the equatorial Pacific Ocean were close to average. Weak warm anomalies were present in the eastern Pacific, across much of the Pacific south of the equator, and in the far western Pacific around eastern Australia, Tasmania, and New Zealand. There has been a general cooling across all areas compared to April.

The May values for the NINO3.4, NINO3 and NINO4 regions were +0.5 °C, +0.5 °C and 0.3 °C, respectively.

The 30-day Southern Oscillation Index (SOI) to 18 June was −4.5 (90-day value −3.6), within neutral territory.

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 18 June was +0.05 °C.

Three out of six climate models predict a positive IOD will develop during late winter to early spring.

A positive IOD typically brings below average winter–spring rainfall to parts of southern and central Australia.

The four-month sequence of sub-surface temperature anomalies (to May) shows water temperatures in the sub-surface of the equatorial Pacific Ocean are generally near average. Areas of weak warm anomalies persist in the top 150 m of the tropical Pacific west of 160°E, while in the eastern tropical Pacific an area of weak cool anomalies is present in the top 100 m between about 120°W and 100°W.

The sub-surface temperature map for the 5 days ending 18 June shows temperatures were generally close to average across the equatorial Pacific Ocean. Compared to two weeks ago warm anomalies near the surface of the eastern tropical Pacific have all but dissipated. Cool anomalies at a depth of 100 to 200 m in the central Pacific also weakened, but continue to reach more than 4 degrees cooler than average for a small area.