The daily AAO [ Antarctic Oscillation Index ]
has gone negative again during the last week or so and is now heading up towards neutral again.
Having watched this index for a year or more and having read a research paper or two on it, it is quite striking how the winter rain events or lack thereof across Victoria seem to closely follow the changes in the AAO index but about a week or so after the AAO Index readings change.
I have also observed over the last year or so that there seems to be a loose correlation between the length of time that the AAO index spends in negative territory and the length of the period where we can expected rain and showers across Victoria particularly southern Victoria.
And the intensity and amount of that rainfall also seems to have a very loose correlation with the range of the negative readings of the index.
The opposite situation also seems to apply when the AAO index goes positive in that we can expect dry weather in Victoria again in a loose correlation with the range of the positive measurements and the length of those positive periods of the Index.
The research papers on the AAO index also suggest that there is an opposite correlation between the northern tropical summer rainfall and the AAO index.
When the Index goes negative during the summer then there is an increased likelihood of some rainfall across our tropical regions.
Conversely with a positive AAO reading the reduced likelihood of rain across our tropical areas during summer.
From what I observed during the summer this does seem to be the case in both cases although the link is not appear to be very strong and is open to question .