Climate Model Summary

Climate Model Summary Archive: September 2014

El Niño remains on hold

Despite significant warming in the tropical Pacific Ocean in the first half of 2014, the ocean and atmosphere largely failed to reinforce each other during the winter months. Subsequently, the chance of an El Niño developing in 2014 has been reduced, however a late forming El Niño still cannot be ruled out. Six out of eight international climate models indicate temperatures in the equatorial Pacific Ocean will be close to or exceed El Niño thresholds by December. There is a reduction in the number of models forecasting El Niño thresholds to be exceeded by the end of 2014.

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) has returned to the neutral range over the previous month after being negative since mid-June. Model outlooks suggest the IOD will remain in the neutral range for the remainder of 2014 and nto the first quarter of 2015.

NINO3.4 outlook

The latest NINO3.4 forecasts (initialised in September) indicate the tropical Pacific Ocean is likely to be warmer than average, but may remain in the neutral range for the remainder of 2014. Most models have a reduced sea surface temperature forecast from last month. Three of the eight models are indicating El Niño thresholds are likely to be reached by December, with a further three models are forecasting temperatures close to El Niño thresholds.

The most recent NINO3.4 value is +0.5 °C for the week ending 14 September 2014. Sustained NINO3.4 values above +0.8 °C indicate El Niño conditions.

Indian Ocean Dipole (IOD) outlook

The Indian Ocean Dipole (IOD) has returned to neutral values over the last month, having been below −0.4 °C (the negative IOD threshold) since mid-June. As negative IOD values persisted for three months, 2014 is considered a negative IOD year. The latest weekly index value (to 14 September 2014) is –0.3 °C, with model outlooks indicating that the tropical Indian Ocean will remain in the neutral range for the remainder of 2014. A negative IOD pattern typically brings wetter conditions to inland and southern Australia during winter and spring.

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 August) 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 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