MEDIUM TERM UPDATE - CAN WE GET BETTER CLARITY?

The frustration continues for many who want rain, for those that don't want any rainfall, for those that want heat, for those that don't want the cold. It is spring and it will irritate! This year is no different!


The weather modelling is volatile as promised back in August, the clarity in the longer term is just not quite there to forecast specifics with any form of confidence. This can be very frustrating, but on the other side of this frustration, we are not looking at any long drawn out blocking pattern.


That opens the door for more dynamic weather events, but the ingredients need to come together. We saw that a couple of weeks ago.


Lets see whether I can answer some questions.

FORECAST - Refer to the video for more details

Moisture Watch Week 1 - September 15-22nd 2021

Main moisture to traverse the country is over the NT right now and another impulse arrives from the northwest, via the jet stream and starts to have impact over SA and the southeast states in the form of more widespread rainfall.

Moisture Watch Week 2 - September 22-29th 2021

Moisture pools over the western inland in the latest modelling, but there is so much divergence in modelling that it is confusing to follow all the arrows, so I have just highlighted the models area of interest.

Rainfall This Week - September 15-22 2021

Moisture over the north becomes absorbed into the jet stream and moved southeast through the nation with patchy rainfall developing later this week. Showers may return to the QLD coast north of Townsville. Much of the inland is dry under sinking air and a dry airmass.

Rainfall Following Week - September 22-29th 2021

Onshore winds along the east coast may bring showers later in the period. Moisture over the western inland of the nation could produce inland showers and storms. As always a low confidence forecast strap is applied through this time as per Spring modelling and lack of real time data really hurting the forecasts at the moment.

Rainfall Anomalies Next 2 Weeks - September 14-29th 2021

Drier than normal weather for the remainder of the month is a higher chance for much of QLD and along the southern coastline, that is measured against what is expected during a fortnight of rainfall at this time of year. The patchy rainfall over the interior will likely bring above average rainfall, but 5-8mm is all it takes in the green zones. The north continuing to get early season showers and storms through the period and then the white shading indicates low confidence for the remainder of the west where modelling supports moisture pooling and being lifted into showers and storms. But we will see.

Temperature Anomalies This Week - September 15-22nd 2021.

Temperature Anomalies Next Week - September 22-29th 2021

DATA

Southern Annular Mode -Next 2 weeks.

Again for those needing to see the SAM again, the weather modelling is highly reactive at the moment and this is the driver which is causing that issue. The SAM trending neutral and then positive and then highly positive on some of the members is creating this divergence in modelling. This driver should remain neutral for the most part, with a positive phase more likely over a negative phase during this period until the end of the month. But as always will keep watching. The neutral phase has little impact on inland rainfall chances increasing, but does keep frontal weather close enough to bring light falls to southern Australia.

Drivers for the next 2 Weeks

18Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 weeks

Watch that system coming out of WA in the second week - perhaps seeing a trend across modelling on moisture increasing over the inland.

18Z GFS - Precipitable Water Values - Next 2 weeks

Moisture is more copious in the modelling this morning as opposed to last night, hence why there is a better coverage in inland rainfall over WA through SA into the southeast, but it is not a trend until I see it on the modelling for 4-6 runs in a row.

18Z GFS - Rainfall - Next 2 Weeks

Refer to the blog video for notes.

More to come in your state based updates this evening with your regional rainfall charts.