Summary: El Niño conditions persist across Pacific
Current Pacific climate patterns are typical for the development phase of an El Niño event. The key indicators include sea-surface temperatures above El Niño thresholds (although there has been some cooling in the past fortnight), sustained negative values of the Southern Oscillation Index (SOI), generally weaker than average Trade Winds since July and increased cloudiness in the central to west Pacific.
However, to qualify as an El Niño event, these key indicators (especially the ocean temperatures) would need to remain at their present levels (the ocean would need to be somewhat warmer) until the end of the year. There is a strong likelihood that this will occur, given what we know from previous events. Furthermore, most computer models indicate continued warming in the Pacific, implying a strengthening of the developing El Niño pattern.
The observed below average rainfall since late autumn across Australia's southern half, especially in the southeast and southwest, is also consistent with the initial phase of an El Niño event, as are the much higher than average daytime temperatures since August. Furthermore, even if El Niño thresholds are not maintained across the range of indicators, a warming Pacific and a low SOI bias the climate towards being drier and warmer than average across eastern and northern Australia for the remainder of 2006. This is reflected in the October-December outlooks for rainfall and temperature.
In Brief
* Pacific climate patterns are indicative of a developing El Niño.
* Equatorial Pacific SSTs are generally over El Niño thresholds.
* Subsurface temperatures have remained warm, though slightly weaker than a fortnight ago. However, recent westerly wind anomalies in the western Pacific have the potential to cause a renewal of warmer subsurface conditions.
* The SOI has fallen to a current (9th October) 30-day value of −10.
* A strong westerly wind burst has emerged in the western Pacific in the past fortnight.
* Cloudiness near the date-line along the equator has been above average during September to early October. In general, cloudiness has been increasing in this area since late May.
* A majority of computer models now predict El Niño conditions developing or persisting in the Pacific during the rest of 2006.
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