Australian Bureau of Meteorology Spring Outlook Released

La Niña and Negative Indian Ocean Dipole Feature in the report.
The Bureau of Meteorology has reported cooling of the surface of the Pacific Ocean and activity involving tropical weather patterns. This report suggests that La Niña could be a feature of spring 2020.

This means that there is likely to be a higher than average level of rainfall for the time of year. This is especially likely on the east coast and in the north, Daytime Temperatures are also likely to be cooler with warmer night temperatures. In addition, there are high chances of more tropical cyclones in the area.

Key points
  • La Nina is predicted to develop over spring months
  • The Indian Ocean Dipole (IOD) index is likely to be negative in spring
  • Increased rain predicted across much of eastern Australia
How likely is the development of La Niña?

The current ENSO Outlook from the Bureau of Meteorology suggests that the likelihood of La Niña forming is around seventy percent. This is treble the average. . 

Although most indications are ENSO-neutral right now, signs are definitely starting to indicate La Niña development. These indicators include the cooling of the central tropical Pacific Ocean. 

The Southern Oscillation Index (SOI) is also above normal La Niña thresholds recently. In addition, the Bureau of Meteorology has surveyed several international climate models. 

They all suggest the development of La Niña with five suggesting that thresholds will be exceeded in October. Six models predict that La Niña will still be around into December. 

Negative Indian Ocean Dipole (IOD) also suggests high rainfall 

All models also suggest that the Indian Ocean Dipole (IOD) index is likely to be negative in spring. However, only half of the models are more definite in predicting a negative IOD. Other models predict a broad range of scenarios, covering equal chances of a neutral to negative IOD. 

If a negative IOD does happen, it will indicate an increased chance of higher than average rainfall across the country. This happens because warm waters off the north-west coast of the country provide more moisture for weather systems. 

In summary 

The release of the Australian Bureau of Meteorology report is important for anyone who is  interested in weather systems across the country. This includes farmers who rely on advantageous weather conditions. The report provides an indication of what temperatures to expect and whether the climate will be wetter or drier overall. It’s worth stating that the predictions in the outlook are not an absolute certainty. 

La Niña – Finance/Economy. Folder on desk with label beside diagrams. Business/statistics. 3d rendering

Therefore, it remains to be seen whether the development of La Niña happens. However, the sea surface temperatures in the tropical Pacific Ocean have dropped by approximately half a degree recently. 

The sub-surface temperatures are also decreasing. This makes it more likely that the surface will continue to cool over the coming weeks. In these conditions, La Niña is likely to develop. This will be an important climate driver. For instance, if this happens at the same time as a negative IOD, spring in Australia could be wetter than average. 

Only time will tell if the Bureau of Meteorology Spring Outlook is an accurate prediction of climate influences. This accuracy will become clearer over the next few weeks as the spring develops from September to November. 

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