We have spoken about the influence of the Indian Ocean this morning in the medium term forecast, but I just wanted to quickly focus on the latest data coming off the global models, that are coming through to my server this morning.
What does it mean for you? How much of a role will it play and when?
12Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks.
There are two systems on the board that are of interest for Australia, which emanate out of the Indian Ocean, bringing a deeper burst of moisture through the jet stream over WA and then feeding troughs over the Central and Eastern parts of Australia with rainfall chances picking up. We can see one system on the approach later this weekend into the SWLD, there will be moisture that comes in on the northern and eastern flank of that low with areas of rain and storms on approach. That then will be pulled through parts of southern Australia into next week, ending September. While that system moves off, another tropical low will be absorbed on this current guide, into the jet stream and weaken due to harsh upper level winds, but the moisture will be drawn throughout the nation once again, reinforcing rainfall chances for much of the nation into early October. While this is ongoing, moisture will be dragged through the eastern inland of Australia via easterly winds.
12Z GFS - Precipitable Water Values - Next 2 Weeks.
The values are increasing throughout the Indian Ocean, we are seeing values of 25-50mm available over a wide area through the area from south of Indonesia and out to the Central Basin. This moisture you can see is then propelled through the jet stream across the nation, and it will come down to the timing of troughs and fronts/low pressure systems as to where this moisture is then lifted into areas of rainfall. Refer to the medium term forecast for more.
12Z GFS - Precipitable Water Anomalies - Next 2 Weeks.
We want to see more green and blue shadings on this chart, rushing in ahead of frontal weather, into the jet stream and converging into troughs, to see rainfall chances pick up from the west over WA but more importantly for states down the line that have missed out. If this moisture can continue to build up further and we lose the cold fronts for a few weeks, then a wet phase for large areas of the nation is quite possible due to a lack of dry air being forced north and sweeping out the rainfall potential. That is what we have been seeing these past few months, finally we have a chance of seeing the pattern finally shift and the Indian Ocean Dipole looks to play its part now with higher moisture values being drawn south and east into the nation for the end of September into October as expected. Fingers crossed.
12Z GFS - Precipitation Anomalies - Next 2 Weeks.
Note that higher precipitation values being drawn southeast just offshore WA, that is what we want to see to see rainfall chances increase for the remainder of spring. This is very important and must verify in real time, not just on the charts.
12Z GFS - Precipitation for Australia - Next 2 Weeks.
As mentioned above refer to the Medium Term Forecast for more on these charts, but essentially, there is that dry slot over the inland of WA, but this could easily change in the coming days as we get closer to the pattern shifting. But the east and southeast wet, is in line with the IOD influence, coupled with the persistent easterly winds thanks to the SAM turning positive.
12Z GFS - Precipitation for Australia - Next 4 Weeks.
Wetter signal grows and starts to fill in that drier area over central and western interior parts, as the moisture content from the Indian Ocean increases, while further rainfall is ongoing for the east and southeast.
12Z Euro - Precipitation for Australia - Next 6 Weeks.
Euro, which is more conservative shows the peak of the IOD and the impacts through October making it quite a concern if you are looking to harvest, it may be a soggy affair and may become an issue to find dry weather IF this verifies, but it is something to watch, consider but not get too concerned about just yet.
I will have more on the next 6 weeks tomorrow as I am looking through data sets this afternoon and the early indication is, if you are looking for dry weather, it may be harder to find, some of the models now increasing the risk of flooding for parts of NSW and VIC.