MOISTURE AND THE INDIAN OCEAN.

A quick note that for those thirsty areas of the nation that has missed out on rainfall opportunities in recent months, more chances are likely to develop into July. Refer to the climate section for more details here


Lets take a look at the current trends over the Indian Ocean as we head into July. This is where the rainfall opportunities are anticipated to increase from. The main ingredient you will hear about during the coming months.


There are many ways to look at the Indian Ocean and the state of play through the region as we track through the coming weeks.


Indian Ocean Basin - Precipitation Anomaly for the coming 2 weeks. GFS 18z Valid Tuesday 29th of June 2021.

High levels of rainfall anomalies by as much as 400-500mm during this period is a signal of what is to come over the course of the latter stages of winter into spring. In the short term the frontal weather is out of phase on current guidance, but it takes one of the fast flow waves to tap into the moisture and drag rainfall back through Australia.

Let's take a look at the various parameters that can see whether the frontal weather can meet the moisture and bring rainfall through the south and west of Australia.


Water Vapour Satellite - Next 10 days - Euro 12z run - Valid Tuesday 29th of June 2021.

This is a great way to identify the amount of fronts rolling through the southern ocean and to also follow the moisture plumes through the mid latitudes, to see whether there will be connection between the frontal boundaries and moisture plumes. You can see multiple bursts of moisture coming through the Indian Ocean, but not quite connecting with the fronts, however this can change run to run! But another useful product to look at in terms of scale and depth of moisture heading into frontal weather or streaming through the jet stream to feed inland troughs, especially over the spring and summer months.

Water Vapour Transport and Direction through the upper levels with surface pressure pattern. GFS next 2 weeks - Valid Tuesday 29th of June 2021.

This product generally shows the movement of moisture from one location to another. We want to see the moisture of those yellow and red tones heading towards Australia and feeding further south and east towards the continent. Not quite seeing that in the current guidance. But this product will be useful in the coming months as the IOD strengthens.

Precipitable Water Anomalies % above normal- Next 10 days - Euro 12z run - Valid Tuesday 29th of June 2021.

Significant PW anomalies can be seen off the NW of Australia, but there is little trigger for this moisture to be utilised and develop rain areas. But the basin does have more moisture than dry air through the period, and with increasing warmer water values over the northern basin, this will only add to the increased PW anomalies in the coming months. Another useful product that I will be using.

Rainfall for the coming 2 weeks - GFS 18z run - Valid Tuesday 29th of June 2021.

Not so much rainfall coming through the jet stream and moisture source during the coming 2 weeks but we have seen multiple looks at this with the model pinging widespread rainfall over WA in recent runs. Just not this run this morning. So we wait over the coming days to see how the model settles closer to the weekend, I firmly believe there will be an increase of cloud and rainfall from northwest to southeast through the nation in the later stages of the first week of July.

KMA Rainfall for the coming 12 days - 12z run - Valid Tuesday 29th of June 2021

More aggressive in utilising the moisture from the northwest in the coming 9-12 day window with a large cloud band being picked up by this model.

So for now it feels quiet but these things can rapidly change and I do firmly believe the rainfall signals will increase again with climatic drivers lifting the westerly wind belt further north next week and the moisture increasing to very high levels just off Australia's northwest.


Need more weather information? Email me at karllijnders@weathermatters.org for more details.


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