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

For the week ending 16 July, 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, with stronger anomalies present around much of east coast and southeast Australia.

The NINO3.4 SST anomaly has remained at around +0.5 °C since mid-April, while NINO3 has held steady around +0.4 °C since mid-June, and NINO4 cooled slightly during the past fortnight to +0.5 °C.

The El Niño-Southern Oscillation (ENSO) remains neutral. All climate models surveyed by the Bureau indicate the tropical Pacific Ocean is likely to stay ENSO neutral for the rest of 2017.

Sea surface temperatures (SSTs) in the central tropical Pacific (the NINO3.4 region) have been warmer than average, though still in the neutral range, since mid-April. The current NINO3.4 value of +0.5 °C is the result of a localised warm anomaly. The overall sea surface temperature pattern is inconsistent with a developing El Niño, meaning further ocean warming and El Niño development remains unlikely. This is reflected in neutral ENSO outlooks from all international climate models surveyed. Other indicators of ENSO, such as the Southern Oscillation Index, cloudiness near the Date Line, and trade winds also remain at neutral levels.

The Indian Ocean Dipole (IOD) is neutral. However, two of six climate models suggest positive IOD thresholds could be reached in the coming months. Only one of these models suggests these will last long enough to be considered a positive IOD event. Positive IOD events are typically associated with below average winter and spring rainfall over central and southern Australia.

Cloudiness near the Date Line during the past two weeks has fluctuated around average values, as it has done for the past three months.

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 16 July 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 of the international climate models surveyed by the Bureau indicate that ENSO-neutral conditions are likely to persist until at least the end of 2017.

SST anomalies for June show sea surface temperatures were slightly warmer than average across most of the equatorial Pacific Ocean. Weak warm anomalies were present across most of the Pacific south of the equator, including around Australia, and also warmer than average in waters around southern and western Australia, to the north of the Maritime Continent, and across large parts of the North Pacific between about 20 and 30°N.

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

The 30-day Southern Oscillation Index (SOI) to 16 July was +0.3 (90-day value −2.9). After a short and sharp dip in late June/early July, the 30-day SOI has returned to the neutral range. 90-day SOI values have remained neutral all year. 

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 16 July was −0.14 °C.

Two out of six climate models indicate the IOD will pass the threshold value for a positive IOD during late winter, but only one model predicts these values will persist long enough to be considered a positive IOD event.

Index values above the positive IOD threshold would need to be sustained for at least eight weeks for an event to be declared. 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 June) shows water temperatures in the sub-surface of the equatorial Pacific Ocean were generally near average. Areas of weak warm anomalies persist in the top 150 m of the tropical Pacific west of 160°E, while an area of weak cool anomalies was present at around 150 m depth to the east of the Date Line.

The sub-surface temperature map for the 5 days ending 16 July shows temperatures were generally close to average across the equatorial Pacific Ocean.