Climate Model Summary

Climate Model Summary Archive: April 2014

Models suggest El Niño likely by mid-winter

All climate models used in this survey suggest that an El Niño will develop by the southern hemisphere spring, with six of the seven models indicating El Niño thresholds are likely to be exceeded as early as July. Currently, the El Niño-Southern Oscillation (ENSO) is neutral, however, patterns in the tropical Pacific Ocean and atmosphere are consistent with the early stages of a developing El Niño.

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 also neutral. Current model outlooks suggest the IOD will remain neutral throughout the forecast period, however, the chance of a positive IOD event is elevated during El Niño events.

NINO3.4 Outlook

The latest NINO3.4 forecasts (initialised in April) indicate the tropical Pacific is likely to warm over the coming months. Most models indicate El Niño thresholds will be exceeded by July, with two models forecasting a more rapid warming trend, with the ensemble mean reaching +1.2 °C by July, while the UKMO model is predicting a more conservative value of +0.5 °C.

The range in forecast values of NINO3.4 is also evident in individual ensemble members (forecast scenarios) from each model with values ranging between +0.2 °C and +3.0 °C by September. (See the 'Models' tab for links to individual model output for NINO3.4).

The most recent NINO3.4 value is +0.3 °C for the week ending 13 April 2014. Sustained NINO3.4 values above +0.8 °C indicate El Niño.

Indian Ocean Dipole (IOD)

The IOD index remains neutral with a latest weekly value of –0.3 °C for the week ending 13 April 2014. The IOD typically has little effect on Australian climate during the months from December to April. This is due to the IOD pattern being unable to form once the monsoon trough moves south over the eastern tropical Indian Ocean. Beyond this time outlooks show a neutral IOD. However, the chance of a positive IOD event is elevated during El Niño.

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 April) predicts NINO3.4 is most likely to remain within neutral values through until June, however, over 90% of the POAMA outlook scenarios (ensemble members) exceed El Niño thresholds in September, indicating a high likelihood of El Niño development. 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