Climate Model Summary Archive: April 2015
Models maintain outlooks for El Niño though winter and spring
The tropical Pacific Ocean has warmed over the last month, with surface temperatures now just shy of typical El Niño values. All surveyed models suggest further warming will occur, potentially exceeding El Niño thresholds in May. Current wind and sub-surface patterns also support further warming of sea surface temperatures in the central and eastern tropical Pacific.
Model forecasts spanning the traditional ENSO transition period, February to May, generally have lower accuracy than forecasts made at other times of year. However, as we are nearing the end of this period, and with all eight models consistent in their outlooks for further warming in the Pacific Ocean, these outlooks cannot be discounted.
The Indian Ocean Dipole (IOD) generally has little impact on Australian climate from December to April due to the natural position of the monsoon trough at this time of year. The latest model outlooks for the IOD index from May are mixed with little to suggest a transition to either a positive or negative phase of the IOD during the current forecast period.
NINO3.4 outlook
The latest NINO3.4 forecasts (initialised in April) indicate the tropical Pacific Ocean is likely to warm over the coming months, with all models indicating El Niño thresholds are likely to be reached or exceeded in May. All models suggest the central Pacific Ocean will continue to warm past mid-year, with the average September (ensemble mean) forecasts for NINO3.4 more than 1.6 °C above normal.
Model forecasts spanning the February to May period tend to have reduced accuracy, and hence greater spread. This period is known as the "predictability barrier" as the temperature gradients across the tropical Pacific Ocean naturally weaken at this time of year, meaning the Pacific can undergo rapid change. Model outlooks for predictions made during this time should generally be used carefully, though a degree of confidence can be placed in the current outlooks as there is strong consensus among the models that warming above El Niño thresholds will occur by June.
The most recent NINO3.4 value is +0.7 °C for the week ending 12 April 2015. NINO3.4 values between –0.8 °C and +0.8 °C typically indicate neutral ENSO conditions.
Indian Ocean Dipole (IOD) outlook
The IOD does not affect Australian climate from December to April. This is due to the monsoon trough moving southwards over the regions of ocean where the IOD occurs. This alters the wind patterns, and results in negative or positive IOD patterns being unable to form during these months.
Current forecasts beyond the December to April low influence period suggest the IOD will remain neutral until at least spring. The state of the tropical Indian Ocean will be monitored closely as the influence of the monsoon weakens during the austral autumn, and the IOD starts to have more influence on Australian climate.
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 12 April) predicts NINO3.4 is likely to continue to warm throughout the forecast period. All ensemble members (forecast scenarios) anticipate El Niño thresholds to be met in May and remain above El Niño thresholds until the end of the year. This agreement amongst ensemble members suggests a higher degree of predictability, despite being in a period where model skill is generally low. 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
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.
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.