Climate Model Summary

Climate Model Summary Archive: November 2014

Models near El Niño thresholds

Recent warming in the tropical Pacific Ocean has pushed model forecasts closer to El Niño thresholds. Most of the models surveyed forecast tropical Pacific Ocean sea surface temperatures to be close to, or exceeding, El Niño thresholds in December, with the average December outlook just over the +0.8 °C threshold.

The chances of 2014 being considered an El Niño year have increased over recent weeks due to atmospheric and oceanic observations in the tropical Pacific. By February 2015, two out of eight international climate models indicate temperatures in the equatorial Pacific Ocean will exceed El Niño thresholds, with four additional models suggesting values close to El Niño thresholds. By April, these same two models persist at El Niño levels, with most other models remaining warm, but easing further into neutral territory.

Warmer central tropical Pacific waters late in the year typically result in warmer and drier weather for parts of eastern Australia, an increase in bushfire risk in the south, and average to below-average numbers of tropical cyclones in the Australian region.

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 November) indicate the tropical Pacific Ocean is likely to be warmer than average over the coming months, with most models suggesting sea surface temperatures (SSTs) will be close to the threshold between neutral and El Niño for the remainder of 2014 and into early 2015. However, a transition to El Niño this late in the year would be considered unusual.

The most recent NINO3.4 value is +0.93 °C for the week ending 16 November 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 16 November 2014) is +0.23 °C, with model outlooks indicating that the tropical Indian Ocean will remain in the neutral range for the remainder of 2014 and into 2015. 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 November) predicts NINO3.4 is likely to remain near El Niño thresholds 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