Thursday, August 20, 2009

Mixed El Niño indicators as development slows

Bureau of Meteorology

19th August 2009

The El Niño pattern across the Pacific has not intensified during the past fortnight. Furthermore, the coupling between the ocean and atmosphere which amplifies and maintains El Niño events has so far failed to eventuate. The neutral SOI and sub-surface cooling are evidence of this.

However, the Trade Winds are weakening over a broad area and this may promote renewed warming. In addition, leading climate models continue to predict further development of the El Niño, although not as emphatically as a month or two back. Therefore, the odds remain strongly in favour of 2009 being recognised as an El Niño year.

July and August have seen below average rainfall across much of eastern Australia, with particularly dry conditions through Queensland and northern NSW. El Niño events are usually (but not always) associated with below normal rainfall in the second half of the year across large parts of southern and inland eastern Australia.

In addition, conditions have recently been very warm for the time of year across Australia, with maximum temperatures consistently more than 4°C above normal over wide areas.

The most recent value of the Indian Ocean Dipole (IOD), as measured by the Dipole Mode Index (DMI), is near zero. The Bureau's POAMA model suggests the DMI should remain neutral over the coming months.

See IOD forecasts, DMI values.

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