Current state of the Pacific and Indian Ocean
El Niño still a possibility for 2014
Issued on Tuesday 12 August 2014 | Product Code IDCKGEWW00
The Pacific Ocean has shown some renewed signs of El Niño development. Some warming has occurred in the central and eastern equatorial Pacific Ocean in the recent fortnight, due to a weakening of the trade winds. If the trade winds remain weak, more warming towards El Niño thresholds is possible.
The Bureau’s ENSO Tracker remains at WATCH status. This means the chance of an El Niño developing in 2014 is at least 50%, which is double the normal likelihood of an event. Five of the eight climate models surveyed by the Bureau suggest El Niño is likely for spring. However, if El Niño were to occur, it is unlikely to be a strong event.
El Niño is often associated with below-average rainfall over southern and eastern inland areas of Australia and above-average daytime temperatures over southern Australia. Similar impacts regularly occur prior to the event becoming fully established.
The Indian Ocean Dipole (IOD) index has been below −0.4 °C (the negative IOD threshold) since mid-June, which means 2014 is now considered a negative IOD year. Model outlooks suggest this negative IOD event is likely to be relatively short-lived, with the Indian Ocean returning to neutral by spring. A negative IOD pattern typically brings wetter winter and spring conditions to inland and southern Australia, and could be countering the effects of the current El Niño-like ocean pattern in the Pacific.
Next update expected on 26 August 2014 | print version
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- Weekly sea surface temperatures
Sea surface temperatures (SSTs) have warmed in the central and eastern tropical Pacific during the past two weeks. Positive anomalies are present along most of the equatorial Pacific, with anomalies close to average in an area of the central Pacific and in the far western Pacific, west of 160°E (see SST anomaly map for the week ending 10 August). Warm anomalies also remain in areas of the Indian Ocean and the northern Pacific Basin, particularly along and adjacent to the coastline of the Americas.
- Monthly sea surface temperatures
The SST anomaly map for July shows the equatorial Pacific cooled compared to the preceding month. July SSTs were warmer than average in the eastern tropical Pacific east of 110°W, extending into the northern Pacific basic, and in an area of the western tropical Pacific just west of the Date Line, with warm anomalies also present to Australia’s northwest and extending into the Indian Ocean.
Baseline period 1961–1990. Index June July Temperature change NINO3 +0.9 +0.7 0.2 °C cooler NINO3.4 +0.5 +0.2 0.3 °C cooler NINO4 +0.6 +0.4 0.2 °C cooler
- 5-day sub-surface temperatures
The sub-surface temperature map for the 5 days ending 10 August shows waters across the equatorial Pacific are generally near average, with waters above around 100 m depth slightly warmer than average. However, it is worth noting that a substantial area of the eastern Pacific has low data coverage (cross markings on image indicate point observations). Other sources of sub-surface data have been considered.
- Monthly sub-surface temperatures
The four-month sequence of sub-surface temperature anomalies (to July) shows a significant break down of warm anomalies in the top 100 m over the past month. The July sub-surface plot doesn’t show a consistent warm signal, with a mixture of weaker warm and cool anomalies across the sub-surface.
- Southern Oscillation Index
The Southern Oscillation Index (SOI) has returned to values around −5 during the past week, following a brief rise to values closer to zero. The latest approximate 30-day SOI value to 10 August is −5.2.
- Trade winds
Westerly wind anomalies have been present over part of the western tropical Pacific, on and to the north of the equator, since late July. Recently, a number of tropical storm systems on the northern side of the tropical Pacific have partially contributed towards these weakened trade winds. Over the remainder of the tropical Pacific winds are near-average (see anomaly map for the 5 days ending 10 August). In westerly wind anomalies in the western Pacific continue they could drive further warming of surface waters in the central and eastern Pacific. Sustained westerly wind anomalies would be a sign that the atmosphere could be falling into alignment with the signs of a developing El Niño in the 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 of the trade winds.
- Cloudiness near the Date Line
Cloudiness near the Date Line has been below average during the past two weeks.
Cloudiness along the equator, near the Date Line, is an important indicator of ENSO conditions, as it typically increases (negative OLR anomalies) near and to the east of the Date Line during El Niño and decreases (positive OLR anomalies) during La Niña.
- Model outlooks
Five of the eight surveyed international climate models continue to indicate that development of an El Niño remains likely by the end of spring. The majority of surveyed models forecast El Niño will persist into summer 2014/15.
- Indian Ocean Dipole
Values of the Indian Ocean Dipole (IOD) have remained in negative territory since mid-June, a period now spanning nine weeks and sufficient for 2014 to be declared an IOD negative year. The latest weekly index value to 10 August is −0.8 °C.
Waters to the south of Indonesia are warmer than average while sea surface temperatures in parts of the Arabian Sea are cooler than average. Climate models surveyed in the model outlooks favour a return to neutral IOD values over the coming months. Typical evolution of IOD events sees a return to neutral conditions by the end of spring or start of summer.