NATIONAL WEATHER UPDATE - PM EDITION - A LOOK AT MOISTURE THROUGH THE INDIAN OCEAN

A quick update on the moisture that will be circulating through the Indian Ocean over the coming two weeks.


Lets look at some of the parameters over the coming 10 days to see why there is an inactive period when all the charts in the medium and longer term are screaming wet wet wet.


Euro 12z - Simulated WV and transportation of the moisture values - next 10 days.

This product shows the moisture values remaining fairly marginal over the coming week which is in line with an inactive phase of convection over Indonesia and south of the archipelago. The region south of Indonesia is the area that we also want to see cranking with convection over the coming months, for now that is not expected and that is why there is an absence of long fetch moisture. We have seen in previous months of that moisture being drawn southeast into the nation has had significant impact on inland rainfall being well above normal. That is likely to return as the Indian Ocean continues to warm. The fact there is uninterrupted sunshine over the ocean will assist in warm the region while the upwelling of warmer values continues. The higher the SST anomalies, the more moisture is available to be drawn into the atmosphere. And a reminder that the warmer the air temperature, the more water the atmosphere can hold, so the rainfall events will increase in scale during the spring and summer as the nation warms.

Euro 12z - PW Values - next 10 days.

I showed this yesterday and will continue to use this product from time to time to give a heads up to rainfall opportunities increasing from the northwest through the southeast. You can see through the outlook period that many ports of moisture is being drawn southeast into the westerly wind belt where larger cloud bands develop. But in the coming 10 days, the jets seem to diverge and there will be an absence of rain bands forming out in the Indian Ocean. The moisture will likely return as we go through August, and all those elevated 2-3 inch PW values will be sheared south and east as the upper pattern shifts. That is expected to place from the second week of August and then you usually tack on another week after that for the moisture to then spread southeast from a given point.

Euro 12z - Simulated Infrared Satellite - next 10 days.

You can see the copious moisture sitting of the northwest of Australia and this product also gives you scale of how vast the ocean mass is out to the northwest of the nation. Convection flaring with the monsoon offshore India will likely increase in the coming weeks as the MJO moves into phase once again, and this is where will see the moisture content increase further, leading to more moisture being drawn into Australia. So for now we are in an inactive phase, but still you can track the moisture being dragged through the nation to produce modest cloud bands and rainfall events. in the coming 10 days. Remember the majority of rainfall over the past week has been without the support of large moisture intrusions from the Indian Ocean.

Euro 12z - Precipitation Anomalies for the coming 10 days.

The Basin is in reset with the moisture pooling southwest of India which is inline with the current MJO phase. That moisture is expected to remain there for the first half of August (black circle). The area that needs to improve in convection is south of Indonesia, which is expected to ramp up into the middle of August (red circle). There is moisture expected to move into this region mid to late next week with that moisture still expected to become stuck. The westerly wind belt is still is quite active over the coming 10 days which is quite normal for the end of July into August. Some evidence that the moisture south of India can be drawn into the jet stream bringing rainfall chances up ahead of cold fronts moving through. These are the areas to watch in the coming months as the event peaks in the September to November.

Rainfall for the coming 2 weeks

Again limited influence from the Indian Ocean over the next week, but there will be enough moisture coming through during the coming 2 weeks to increase rainfall along frontal systems. You will see that with the front coming over WA and then into the southeast inland with light and patchy rainfall with a larger cloud band, but the moisture is not super deep and the lifting mechanism weakening on approach to the east. That will repeat again during Friday into the weekend and possibly again early next week. It is when we get moisture coming in from Indonesia through the northwest of the nation we will see rainfall increase.

Jetstream/Moisture now vs what the pattern flip will look like?

This is the current moisture track this week (white) with limited moisture surging into the long wave coming into WA, we have seen a portion of that upper level moisture shear off through QLD with weakening upper winds and suppressed under upper high pressure. It is when we see the moisture come in from the better angle (yellow) through from Java into Australia and picked up by troughs and low pressure building in response to the heating of the continent, that is where rainfall becomes more widespread. So it may be quiet now for a lot of inland Australia but the shift will come and the tap may not just be turned on gently, but possibly on full blast and not stop for a while. So just make preparations now for the possibility of widespread rainfall, possibly heavy and frequent, only a matter of weeks away.

More on this coming up in the Climate Outlook tomorrow.

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