Summary: The 2006/07 El Niño has ended
The 2006/07 El Niño has ended. All the main ENSO indicators show that neutral conditions have returned to the Pacific Basin. Along the equator, sea-surface temperatures are cooling rapidly and have been below their El Niño thresholds for about a month now. The Trade Winds have mostly been close to or somewhat stronger than normal since December, the SOI has been neutral for three of the past four months and central-western Pacific cloudiness is close to average. Computer models indicate further cooling in the Pacific, with a La Niña not out of the question (see third paragraph).
What does this mean for Australia? Firstly, while the end of the El Niño would normally be associated with a return to more normal rainfall patterns, it should not be seen as a precursor to drought-breaking rains. This particularly applies to water supplies in parts of eastern and southern Australia, which in some instances require several years of healthy rainfalls to recover to a satisfactory level. Nonetheless, we can be cautiously optimistic that there will be a general easing of dry conditions in drought-affected areas over the next one to two seasons.
A La Niña in 2007?
The chance of a La Niña developing in 2007 is thought to be higher than the long-term average (which is about one in five or 20%) because (a) they have a tendency to follow an El Niño; (b) the El Niño has decayed somewhat earlier than normal thereby giving time for a La Niña to begin developing during the critical March to June period; and (c) a large pool of cold sub-surface water has developed in the central to eastern tropical Pacific Ocean. La Niña events are generally associated with wetter than normal conditions across much of the eastern half of the country from about autumn.
In Brief
* Equatorial Pacific SSTs have further cooled and are below El Niño thresholds.
* Negative subsurface anomalies have strengthened and reached the surface in the eastern Pacific.
* The SOI has a current (19th January) 30-day value of −3.
* Trade Winds have generally been close to or somewhat stronger than average in the western Pacific during February.
* Cloudiness near the date-line has recently been close to average.
* Most computer models predict cool neutral conditions in the first half of 2007.
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