Hello all, good to hear about huge wet coming up during this year.
Summary: Conditions currently neutral; La Niņa chances remain elevated
Equatorial Pacific sea-surface temperatures have cooled slightly during April, but remain close to average. The Trade Winds have been generally stronger than normal during recent months, while cloudiness in the western-central Pacific has been close to average for the past month. Overall, these ENSO indicators are neutral. The SOI on the other hand, has dropped below −10 during April thereby raising concerns about continued dry weather in eastern Australia. However, the SOI often shows increased monthly fluctuations at this time of year, so at this stage there is no longer-term significance in the SOI behaviour. There appears to be little chance of a return to El Niņo conditions in 2007, with a continuation of neutral, or a switch to La Niņa conditions, the more likely outcomes.
A La Niņa in 2007?
The chance of a La Niņa 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 Niņo; (b) the 2006/07 El Niņo decayed somewhat earlier than normal thereby giving time for a La Niņa to begin developing during the critical March to June period; (c) several of the better computer models are predicting one to occur; and (d) a large pool of cold sub-surface water is persisting in the central to eastern tropical Pacific Ocean.
The cold sub-surface water has promoted the development of a narrow tongue of below-average temperatures on the surface of the eastern equatorial Pacific. This may be the first sign of an emerging La Niņa, but it will be a few months yet before a clear trend becomes evident. La Niņa events are generally associated with wetter than normal conditions across much of the eastern half of the country from about autumn.
In Brief
- Negative SST anomalies persist in the eastern equatorial Pacific.
- Negative subsurface anomalies have strengthened in the central-eastern equatorial Pacific.
- The SOI has a current (22nd April) 30-day value of approximately −12.
- Trade Winds have generally been close to average in the equatorial Pacific in recent weeks, they are currently slightly stronger than average in the central Pacific.
- Cloudiness near the date-line has recently been close to or slightly below average.
- Many computer models predict further cooling of the Pacific during the first half of 2007, with some of the better ones predicting the development of La Niņa conditions.
