The current El Niño Pacific Ocean warming event is producing sea surface temperatures not seen since the 1997–98 event while the Indian Ocean remains exceptionaly warm, according to the Australian Bureau of Meteorology (BoM).
Tropical Pacific sea surface temperatures are more than 2 °C above average, exceeding El Niño thresholds by well over 1 °C. Most international climate models surveyed by the BoM indicate El Niño is likely to peak towards the end of 2015 and persist into 2016, a story published by the reportingclimatescience.com yesterday.
The tropical Pacific ocean and atmosphere are reinforcing each other, maintaining a strong El Niño that is likely to persist into early 2016. Tropical Pacific sea surface temperatures are more than 2 °C above average, exceeding El Niño thresholds by well over 1 °C, and at levels not seen since the 1997–98 event. In the atmosphere, tropical cloudiness has shifted east, trade winds have been consistently weaker than normal, and the Southern Oscillation Index (SOI) is strongly negative.
Most international climate models surveyed by the Bureau of Meteorology indicate El Niño is likely to peak towards the end of 2015. Typically, El Niño is strongest during the late austral spring or early summer, and weakens during late summer to autumn.
The Indian Ocean Dipole (IOD) is in a positive phase, having exceeded the +0.4 °C threshold for the past 8 weeks. Recent values of the IOD index have been at levels not seen since the strong 2006 positive IOD event. Conversely, the Indian Ocean remains very warm on the broader scale.
Four out of five international models suggest the 2015 positive IOD event will persist until November, when it typically breaks down due to monsoon development.
El Niño is usually associated with below-average spring rainfall over eastern Australia, and increased spring and summer temperatures for southern and eastern Australia. A positive IOD typically reinforces the drying pattern, particularly in the southeast. However, sea surface temperatures across the whole Indian Ocean basin have been at record warm levels, and appear to be off-setting the influence of these two climate drivers in some areas.
Warm anomalies persist along the equator from the South American coast to the Date Line and across most of the Pacific Ocean east of the Date Line in the northern hemisphere. Compared to two weeks ago, sea surface temperature (SST) anomalies have increased slightly in the eastern equatorial Pacific and remain similar in the central and western equatorial Pacific.
Anomalies for the week ending 27 September 2015 exceed +2 °C across most of the equatorial Pacific east of 170°W. Warm anomalies are also present in areas to Australia’s west, and across the majority of the Indian Ocean.
All five NINO indices remain above +1 °C this week, and both NINO3 and NINO3.4 remain at or above +2 °C. NINO3 and NINO3.4 were last at these levels during the 1997–98 El Niño.