Climate Model Summary
IOD and ENSO likely to be neutral for first quarter of 2020
The strong positive Indian Ocean Dipole (IOD) event of 2019 has ended. This positive IOD event resulted in widespread drier and warmer than average conditions across much of Australia and nearby regions such as Indonesia, with its decay occurring about a month later than usual. The IOD typically has little impact on Australian climate during summer and early autumn.
The El Niño–Southern Oscillation (ENSO) is also neutral, however warmer than average sea surface temperatures in the western tropical Pacific may be contributing to some changes in weather patterns over the region. The latest outlooks from the surveyed models suggest that an ENSO-neutral state is the most likely scenario through autumn 2020.
The latest weekly NINO3.4 value to 19 January is +0.4 °C, continuing within ENSO-neutral bounds. All but one of the surveyed models suggest the central tropical Pacific (NINO3.4) will remain neutral through to at least May 2020. One model suggests La Niña thresholds may be met from April.
An ENSO-neutral state means that the El Niño–Southern Oscillation has little influence on Australian or global climate.
Indian Ocean Dipole (IOD) outlook
The positive IOD event has ended. This is much later than usual for a typical IOD event. The 2019 positive IOD was the strongest such event since 1997 and heavily influenced the widespread warm and dry conditions across Australia in the latter half of 2019.
The Indian Ocean showed patterns consistent with a positive IOD event from the end of May, peaking in mid-October, before returning to neutral values in the last week of December. The latest value (for the week ending 19 January) is +0.1 °C, below the +0.4 °C threshold for a positive IOD event.
IOD events are typically unable to form during the southern summer and early autumn. This is because the monsoon trough shifts south over the tropical Indian Ocean, changing the wind patterns which prevents the IOD pattern from being able to form. The IOD therefore has little effect on Australian climate at this time of year.
Australian Community Climate Earth-System Simulator–Seasonal (ACCESS–S)
The Bureau of Meteorology's climate model generates a six-month forecast for the NINO and IOD indices each fortnight.
The most recent model run (generated 18 January) suggests sea surface temperatures in the central tropical Pacific (NINO3.4) will remain warmer than average but generally neutral until the southern winter. While temperatures briefly touch on El Niño thresholds in early autumn, they aren't likely to persist, with near-average values again forecast by May. For the Indian Ocean Dipole (IOD), the Bureau's model indicates the IOD index values will remain neutral throughout the remainder of summer and autumn.
The forecast values, shown below in bold, are for the model's ensemble mean.
Product code: IDCKGL0000
Average of international model outlooks for NINO3.4
Average of international model outlooks for the Indian Ocean Dipole (IOD)
The arrows on the dials indicate the combined average of monthly outlooks from a survey of international global climate models. Note that the individual model runs vary around the average.
NINO3.4 covers the central Pacific region.
The graphs are based on the ensemble mean for the most recent model run.
These graphs show 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.
The graphs are based on the ensemble mean for the most recent model run.
Thse graphs show 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.
Sea surface temperature graphs
NINO34 predictions for the next 5 months.
About these sea surface temperature outlooks
About the graphs
The plume graphs show outlook scenarios for sea surface temperatures (SSTs) averaged over particular regions of the Pacific and Indian oceans. The SSTs in these regions are related to different phases of the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD); climate drivers that can influence Australian rainfall and temperature patterns.
The graphs show 99 possible scenarios (grey lines), that are produced by the Bureau's climate outlook model, which represent the range of outcomes that may occur over the forecast period. For example, they may show the SSTs in the NINO3.4 region to be warming, cooling, or remaining mostly steady. At times the outlook might suggest a shift towards (or away from) values typically associated with El Niño or La Niña events. Each of the 99 scenarios is based on current conditions in the global oceans/atmosphere and how the model anticipates their likely development over the outlook period, with each given slightly different treatment to provide a range of likely possibilities. This technique allows us to see the range of what is possible, with a small spread in the range of scenarios meaning more confidence in the likely path, and a larger spread meaning less confidence.
The green line is the average of all these 99 scenarios, often known as the ensemble mean. The solid black line shows the observations (based on the Bureau's SST observation analysis for each region) for the previous months.
The graphs are updated fortnightly. As a result, the value given for the 'current month' can vary depending on at what point in the month the forecast is being issued. Forecasts made on the 1st to the 11th of the month show a forecast value for the current month. For forecasts made after the 11th of the month, a month-to-date observation (shown by an open circle and dashed line), based on weekly observational data, will be used for the current month as a preliminary value until the final monthly data is available.
About the maps
While the climate model runs a set of 99 possible scenarios, it can be useful to look at the ensemble mean (the average of these forecasts) to see the most likely scenario. The global SST maps show the most likely SST anomaly for the months and seasons ahead. This can be useful to see how ENSO and IOD look spatially. The SST anomalies show the difference from the 1990-2012 average (often referred to as the base period).
About the outlook model
The long-range SST outlooks are generated by the Bureau's climate model, ACCESS–S (Australian Community Climate Earth-System Simulator–Seasonal). ACCESS–S is the Bureau of Meteorology's dynamical (physics-based) weather and climate model used for monthly, seasonal and longer-lead climate outlooks. Prior to August 2018, climate outlooks (including these graphs) were produced by the Bureau's earlier model, POAMA.
Product code: IDCK000073
The models used within our survey are listed below with links to their agency homepages, model output and technical information about the model.
Model data are provided for Bureau of Meteorology use by the agencies detailed in the Models section. Respective agency copyright applies to these data.