Climate Model Summary Archive: December 2014

Tropical Pacific Ocean likely to remain near El Niño thresholds over summer

The tropical Pacific Ocean remains warm, with surface temperatures exceeding El Niño thresholds for several weeks now. However atmospheric indicators of El Niño, such as the trade winds, cloudiness and tropical rainfall, are yet to show widespread and sustained patterns consistent with El Niño.

Most of the surveyed models forecast tropical Pacific Ocean sea surface temperatures to remain near, or just above, El Niño thresholds in January. Most models indicate NINO3.4 will peak at its maximum temperature in the coming months and then begin to cool. However, all models predict NINO3.4 will still be on the warm side of neutral in May 2015.

Two models indicate El Niño thresholds will continue to be exceeded in May 2015. Model forecasts spanning the autumn months tend to have reduced accuracy than at other times of the year and should therefore be treated with caution.

The Indian Ocean Dipole (IOD) has no observed impact on Australian climate from December to April due to the natural position of the monsoon trough at this time of year.

NINO3.4 outlook

The latest NINO3.4 forecasts (initialised in December) indicate the tropical Pacific Ocean is likely to be warmer than average over the coming months, with most models suggesting sea surface temperatures (SSTs) will be close to, or above, the El Niño threshold for the remainder of the 2014-15 summer. A transition to El Niño this late in the year would be considered unusual.

Two models suggest SSTs will continue to exceed El Niño thresholds until at least May, however, model forecasts spanning the autumn months tend to have reduced accuracy than at other times of the year and should therefore be treated with caution.

The most recent NINO3.4 value is +0.9 °C for the week ending 14 December 2014. Sustained NINO3.4 values above +0.8 °C can indicate El Niño conditions. NINO3.4 has been above this threshold for five weeks now. In this situation, the atmosphere is yet to show a widespread and consistent El Niño signal.

Indian Ocean Dipole (IOD) outlook

The Indian Ocean Dipole (IOD) is neutral. The IOD does not impact on Australian climate from December to April. This is due to the monsoon trough moving southwards over the regions of ocean where the IOD pattern occurs. This alters the wind patterns, and results in the IOD pattern being unable to form during these months.

The following graph shows the average forecast value of the IOD index for each international model surveyed for the selected calendar month. If the majority of models are approaching or exceeding the blue dashed line, then there is an increased risk of a negative IOD event. If the majority of models are approaching or exceeding the red dashed line, then there is an increased risk of a positive IOD event.

Predictive Ocean Atmosphere Model for Australia (POAMA)

POAMA, run at the Bureau of Meteorology, generates an eight-month forecast each fortnight. The most recent model run (started on 14 December) predicts NINO3.4 is likely to drop just below El Niño thresholds in January, with a gradual cooling throughout the forecast period although remaining warmer than normal. The following forecast values (at the top of the table) are for POAMA's ensemble mean.

POAMA archive data is available here.

ENSO Dials

The arrows on the dials below indicate the combined average ofmonthly NINO3.4 outlooks from a survey of international global climate models. Note that the individual model runs vary around the average.

NINO3.4 outlook bar-graphs

The following graphs shows the average forecast value of NINO3.4 for each international model surveyed for the selected calendar month. If the bars on the graph are approaching or exceeding the blue dashed line, there is an increased risk of La Niña. Similarly, if the bars on the graph are approaching or exceeding the red dashed line, there is an increased chance of El Niño.

IOD outlook bar-graphs

Past climate model summaries

October 2015 El Niño to peak towards end of 2015; rapid decay likely in first quarter of 2016
September 2015 El Niño set to persist at strongest values since 1997-98
August 2015 Models maintain El Niño into 2016
July 2015 El Niño likely to strengthen and persist through 2015
June 2015 El Niño likely to strengthen during spring.
May 2015 Models indicate tropical Pacific to remain well above El Niño thresholds.
April 2015 Models maintain outlooks for El Niño through winter and spring.
March 2015 Model consensus indicates El Niño by winter 2015.
February 2015 ENSO neutral, though tropical Pacific Ocean likely to remain warm.
January 2015 Models suggesting neutral for now, but remaining warm.
December 2014 Tropical Pacific Ocean likely to remain near El Niño thresholds over summer.
November 2014 Models near El Niño thresholds.
October 2014 Models ease outlooks for El Niño in summer.
September 2014 El Niño remains on hold.
August 2014 Models ease their El Niño outlook for spring.
July 2014 Majority of models still favour spring El Niño.
June 2014 El Niño remains likely for 2014.
May 2014 El Niño remains likely for 2014.
April 2014 Models suggest El Niño likely by mid-winter.
March 2014 An increased chance of El Niño from winter.
February 2014 Models indicate tropical Pacific to warm.
January 2014 Models suggest tropical Pacific likely to warm over coming months.
December 2013 Neutral ENSO through summer.
November 2013 Neutral ENSO through summer.
October 2013 Neutral ENSO for austral summer.
September 2013 ENSO and IOD neutral.
August 2013 ENSO neutral; negative IOD weakening.
July 2013 ENSO remains neutral; negative IOD likely
June 2013 Negative IOD, but ENSO remains neutral.
May 2013 Neutral ENSO, possible negative IOD development.
April 2013 Neutral ENSO conditions expected to persist.
March 2013 ENSO neutral set to continue.
February 2013 Models predict neutral conditions to continue.
19 September 2012 Pacific remains close to El Niño thresholds.
5 September 2012 Borderline El Niño conditions continue.
22 August 2012 El Niño remains likely for 2012.
8 August 2012 Models predict weak El Niño in 2012.
25 July 2012 El Niño remains likely in 2012.
11 July 2012 Models suggest increased risk of El Niño in 2012.
27 June 2012 Models suggest further warming through winter.
13 June 2012 Models suggest further warming through winter.
30 May 2012 Neutral in tropical Pacific, but further warming likely.
16 May 2012 Warming in tropical Pacific set to continue.
2 May 2012 Neutral conditions, but warming in tropical Pacific continues.
18 April 2012 Continued warming in tropical Pacific Ocean.
4 April 2012 La Niña ends; conditions neutral.
26 October 2011 La Niña re-established in the Pacific.
27 April 2011 Models predict neutral conditions by southern hemisphere winter.
30 March 2011 Models predict continued weakening of La Niña conditions.
2 March 2011 Models predict continued weakening of La Niña conditions.
2 February 2011 Models predict La Niña will persist into the southern hemisphere autumn.
18 January 2011 Models predict La Niña event will persist through southern hemisphere summer.
8 November 2010 Models predict La Niña event will persist into first quarter of 2011.
27 October 2010 Models predict La Niña event will persist into at least early 2011.
13 October 2010 Models predict La Niña event likely to continue until at least early 2011.
29 September 2010 Models predict La Niña event to continue through 2010.
15 September 2010 Models predict La Niña conditions to continue: La Niña intensifies in the Pacific.
1 September 2010 Models predict conditions to remain above La Niña thresholds: La Niña strengthens in the Pacific.
18 August 2010 Models predict continued cooling in the tropical Pacific: La Niña conditions persist in the Pacific.
31 May 2010 Models predict neutral conditions to persist over coming months, with the possibility of cool conditions later in the year.
April 2010 Models predict neutral conditions to persist over coming months, with the possibility of cool conditions later in the year.
March 2010 Models predict neutral conditions to return to the Pacific by June 2010.
November 2009 Models predict that El Niño conditions will persist through summer 2009/10.