COULD THE INDIAN OCEAN BE WAKING UP AS WE HEAD INTO JULY?

Updated: 11 hours ago

Better signals in the latest update from the Climate Modelling, with strong signals for rainfall developing over northwest parts of the nation and extending southeast through southeast areas of the nation, with that signal increasing in July.


That is in line with the latest data and forecast from the POAMA/BOM model bringing a negative phase in the IOD.


Indian Ocean Dipole Forecast for the remainder of 2021 - BoM/POAMA model. Valid June 8th 2021.

With the trend in the modelling to increase a negative IOD through July onwards into the spring, this bodes well for rainfall chances to increase over parts of southern and eastern Australia, with extensive cloud bands anticipated to develop along the jet stream.


Global Modelling Summary - Indian Ocean Dipole September 2021 - Valid June 8th 2021

The mean may be just below the thresholds for a negative dipole to be declared, however these values are increasing negative each update.

Image - Bureau of Meteorology.

Global Modelling Summary - Indian Ocean Dipole October 2021 - Valid June 8th 2021

The signal continues into October and this being at place during mid spring, would see a higher chance of major rainfall events over inland areas of Australia including southern and eastern Australia.

Image -Bureau of Meteorology.

The SSTs forecast is remaining warm for the Indian Ocean, with the chance of these values increasing as we go through spring, increasing the chance of rainfall numbers picking up over much of Australia for the back half of 2021. This is not factoring a chance that La Nina could redevelop over the Pacific, with signals increasing on that front too, but not enough for me to get too excited just yet.


SSTs anomalies forecast for July-September 2021. Positive signs around Australia. Note the Pacific is remaining neutral so the risk of an El Nino this year are near 0% and the risk of neutral remains the most likely outcome, though the La Nina phase chances are increasing.

Image - Bureau of Meteorology.

So when do we start to see the impacts of the IOD?


Well how long is a piece of string as I get told often. In my opinion, you feel the impacts of the IOD as you track through July and more often through August into October as the event peaks, so rainfall would increase from July, and peak through October, and begin to wane from November as the event becomes neutralised in the Austral Summer. But not one event is always the same and so you have to take it month to month.


The medium term signals are seeing the Indian Ocean waking up into the negative phase and now drawing in some larger rainfall events spreading in from the northwest into July. So will watch these trends.


Euro medium term rainfall spread - Valid Friday June 11th 2021.


So if you are looking for more rainfall, the signals are good, especially for areas that have been on the lean side so far this winter. Where you live is important to how much rainfall you will see above normal - obviously the outback does not see much rainfall through winter but when an IOD is in phase to bring rainfall, these areas can see excessive rainfall against the average, which would be quite normal in coastal areas.


Remember, if you like in Broken Hill or Moomba or parts of the Riverlands in SA, you are not living in QLD where you are going to see 1000mm of rainfall. It does not work like that, so manage the expectations about what one would expect in a situation like this. Rainfall chances are improving, but it could be more rainfall days that brings you average rainfall for 6 months, it could be less rainfall days that brings you above average falls. No one knows the speicifics.


The overall trend for rainfall to increase is positive and leaving it that for now is fair.

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