Climate Model Summary

Climate Model Summary Archive: October 2014

Models ease outlooks for El Niño in summer

Despite some recent warming in the tropical Pacific Ocean and fluctuating El Niño signals in the oceans and atmosphere since April, ENSO (El Niño-Southern Oscillation) remains neutral. While a number of models indicate that El Niño thresholds will be exceeded by early January, overall consensus is that the chance of a late-forming El Niño has been reduced. By January 2014, only three out of eight international climate models indicate temperatures in the equatorial Pacific Ocean will exceed El Niño thresholds, with two additional models suggesting values close to El Niño thresholds.

El Niño is often, but not always, associated with below-average rainfall during the second half of the year across large parts of southern and inland eastern Australia. Daytime temperatures also tend to be above average over southern Australia.

The Indian Ocean Dipole (IOD) is neutral, following a brief negative phase during winter. The IOD has little influence on Australian climate during the summer months.

NINO3.4 outlook

The latest NINO3.4 forecasts (initialised in October) indicate the tropical Pacific Ocean is likely to be warmer than average, but remain in the neutral ENSO range for the remainder of 2014. Most models have eased their outlooks from last month, however three models continue to suggest El Niño thresholds will be met by January and persist until at least March. Two additional models indicate sea surface temperatures are likely to approach El Niño thresholds in January, and another model by March. However, a transition to El Niño during these times is unusual.

The most recent NINO3.4 value is +0.5 °C for the week ending 12 October 2014. Sustained NINO3.4 values above +0.8 °C indicate El Niño conditions.

Indian Ocean Dipole (IOD) outlook

The Indian Ocean Dipole (IOD) is neutral following a brief negative phase during winter. The latest weekly index value (to 12 October 2014) is +0.4 °C, with model outlooks indicating that the tropical Indian Ocean will remain in the neutral range for the remainder of 2014. The IOD has minimal influence on Australian climate during the summer 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-monthly forecast on the first day of each month. The most recent model run (started in October) predicts NINO3.4 is likely to remain well within neutral bounds throughout the forecast period. The following forecast values (at the top of the table) are for the ensemble mean.

POAMA archive data is currently not available. The most recent POAMA run 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.

ENSO dial month+1 ENSO dial month+3 ENSO dial month+5

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.

NINO3.4 bar graph month+1 NINO3.4 bar graph month+3 NINO3.4 bar graph month+5

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.

IOD bar graph month+1 IOD bar graph month+3 IOD bar graph month+5

Past climate model summaries