Ag Weather Forum

Australia El Nino Update

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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Following are selected comments from the latest Pacific Ocean analysis done by the Australia Bureau of Meteorology. This agency is still calling for El Nino development in the Pacific, despite a recent relaxing of the atmospheric indicator known as the Southern Oscillation Index (SOI).--Bryce

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The 2015 El Nino continues to develop. International climate models surveyed by the Bureau of Meteorology suggest further warming of the tropical Pacific is likely, with sea surface temperatures forecast to remain above El Nino thresholds for the remainder of the year.

Most oceanic and atmospheric indicators are consistent with El Nino. Sea surface temperatures in the tropical Pacific have continued to warm, and trade winds have been consistently weaker than average. However, the Southern Oscillation Index (SOI) is currently rising, with this due to local weather, not climate factors. In the past three months the SOI has averaged −9.7, exceeding El Nino thresholds. Cloudiness near the International Date Line has also eased towards more normal levels, but this shift may only be short-lived.

The sea surface temperature (SST) map for the week ending June 7 2015 clearly shows an El Nino pattern in the tropical Pacific region, with a warm tongue extending across the equatorial Pacific from the South American coastline. Warm anomalies over the past fortnight have increased across most of the equatorial tropical Pacific. The warm tongue of positive anomalies currently extends well past the Date Line, with much of this region in excess of +1 degree Celsius, and small areas in excess of +2 deg C starting to appear in the eastern to central regions. All five NINO indices are at least +1.2 deg C above normal. It is unusual to have such a broad extent of warmth across the tropical Pacific; this has not been seen since the El Nino event of 1997-98.

The SST anomaly map for May 2015 shows positive anomalies across the equatorial Pacific. These positive anomalies extend from the South American coastline, and past the International Date Line to around 160 degrees East. The northeast Pacific Ocean continues to remain above average, while SST anomalies surrounding Australia cooled compared to April, with May anomalies in the Australian region generally close to average. All five NINO indices averaged over the month were greater than +1 degree Celsius, which again has not occurred since the El Nino of 1997-98.

All eight of the surveyed international climate models indicate the central Pacific Ocean will warm further during the coming months. All surveyed models indicate that NINO3.4 will remain above El Nino thresholds through the southern hemisphere winter and at least through to the end of the year.

(ES)

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