For those tracking the medium term forecasting, there are signs that the wet signal and colder weather for southern Australia will remain in place for large parts of Australia.
The jet stream now starting to respond to a warmer than normal jet stream bringing large cloud bands with rainfall potential over the nation. That will mean that parts of the interior could see well below average temperatures and more rainfall than usual.
GFS Precipitable Water Values - Next 2 weeks - Valid Friday June 18th 2021.
The moisture within the jet stream remains active for the coming 2 weeks, one impulse comes down the pipe this week and may be fully realised in it's potential if it can connect/be in phase with the front rolling through the southwest of the nation. This will be a great signal for how the coming season may behave as the negative IOD becomes established and matures.
So as a consequence the short term rainfall is looking quite wet over large areas thanks to the negative Indian Ocean Dipole. And with how it works in theory, you can see it play out in real time.
Negative Indian Ocean Dipole Influence on moisture/rainfall through the country. This is a guide and not an absolute rule, however this is where you expect to see the impacts.
Rainfall Outlook - Seasonal - July through September 2021
The consequence on rainfall outlooks are usually to increase the chances of above median rainfall through the season when the negative IOD is in place. We are seeing that in the climate models and the forecasts for the coming months. However it should be noted that the rainfall chances being quite elevated over inland parts of Australia is quite easily achieved and so though impressive, in context, it is the dry season. The higher chances that sit over areas that should be wet, is a more impressive signal.
Temperature Outlook - Seasonal - July through September 2021
Increased cloudiness over the southern two thirds of the nation can bring a period of below average temperatures in association with higher rainfall chances. The negative IOD though has the influence of bringing up the day time temperatures over northern Australia, as higher humidity values appear and interrupt the dry season weather.
In the short term we are seeing the cloud bands develop in association with the moisture coming out of the Indian Ocean. Once a strong cold front approaches WA later Saturday into Sunday, this moisture will be drawn south and increase in volume. Widespread rain is likely to break out from this high and middle level cloud during Monday and Tuesday before moving to the east, taking rain with it to inland areas.
National Satellite Picture - Valid Friday 18th of June 2021.
Note the cloud band coming out of the Indonesia region through the Indian Ocean and into the northwest of the nation as the jet stream becomes moisture laden.
Note the rain band rolling through the nation in response to the front coming over WA and then a low forming off WA with strong gusty winds and rainfall spreading from west to east next week.
So rainfall charts will become more colourful at times over the coming weeks, but the totals will likely become heavier as we go through spring and the nation warms up with the seasonal shift, especially if the negative IOD is in place and maturing during this time, so we may have to start thinking about flood risks, especially if rainfall is in the upper % range of what we expect during this time. In 2016, a negative IOD brought flooding through large parts of inland Australia.
Rainfall for the next 10 days - Valid Friday 18th of June 2021