Climate Model Summary

Climate Model Summary Archive: January 2015

Models suggesting neutral for now, but remaining warm

The tropical Pacific Ocean has cooled rapidly in recent weeks, since peaking in mid-December with surface temperatures briefly reaching values typical of El Niño. Current values of the NINO3.4 index in the central tropical Pacific are now well within the neutral range.

Most of the surveyed models forecast tropical Pacific Ocean sea surface temperatures to remain above average, but within the neutral range, until at least April. Three models suggest renewed warming in June, with the value of NINO3.4 forecast to reach El Niño thresholds by this time, while the other five models remain neutral. 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 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 January) indicate the tropical Pacific Ocean is likely to be warmer than average over the coming months, but remaining within the neutral range until at least April. Three models suggest the central tropical Pacific is likely to experience warming during autumn-winter, with two forecasting NINO3.4 values to exceed El Niño thresholds by June. The third model only briefly reaches threshold values before dropping back to neutral. Neutral conditions are forecast throughout the period by the remaining five models.

Model forecasts spanning the autumn months tend to have reduced accuracy than at other times of the year. This period is known as the "autumn predictability barrier" as the temperature gradients across the tropical Pacific Ocean naturally weaken at this time of year. Model outlooks for predictions through autumn and beyond should therefore be treated with caution.

The most recent NINO3.4 value is +0.4 °C for the week ending 11 January 2015. NINO3.4 values between –0.8 °C and +0.8 °C typically indicate neutral ENSO conditions.

Indian Ocean Dipole (IOD) outlook

The Indian Ocean Dipole (IOD) is neutral. 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.

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 4 January) predicts NINO3.4 is likely to warm gradually, although remain neutral, throughout the autumn and winter months. 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.

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