NATIONAL WEATHER WRAP - TEMPERATURES REMAIN VOLATILE WITH RAINFALL SCATTERED OVER THE NATION

Spring time certainly showing itself early this year, despite being September, this weather we are seeing is typical of what you would see in early October with large temperature drops and rainfall scattered over the nation.


We have got another system coming through WA, which promised so much last week for SA, VIC and NSW, but it appears that it is just a standard front now with not much attached to it, however it could still surprise in some locations.


The tropics are waking up too, this is helping to produce more moisture. That moisture is likely to be transported further south and east, even starting from this week. We just need a trough or front to lift it into showers/storms and areas of rain.


Lets take a look at the latest details.

Rainfall for the next 10 days

Rainfall again lean for many areas, but there are signals of that seasonal shift across the nation. Note the connection back to the tropics, it is not as heavy as what was forecast last week as the guidance supports the cold front diving south and being decoupled from the moisture coming out of the northwest of the nation. Otherwise the bulk of the wet weather likely to be over Cape York and the SWLD of WA. Moderate shower coverage in the short term over the east coast of NSW will be welcome as many areas have missed out along the coast. But for Ag areas of SA and VIC, light falls for now.

Thunderstorm Forecast Monday

The storm focus should shift into NSW today, with the showers becoming lower topped through VIC as the air warms up. The storm focus over NSW is non severe and will be random and scattered this afternoon in line with the day time heating process. Some of these showers and storms could be gusty.

Hail Risk Forecast

Again this risk has largely eased from overnight through VIC with the main risk in NSW this afternoon and evening. Small hail is likely with any tall shower or low topped thunderstorm.

DATA - GFS used in the video - can compare with the Euro Below


Euro 12z - Surface Pressure Pattern - next 10 days

Upper trough and cold pool over the southeast lifts towards the NSW coast today and combines with onshore winds to lift rainfall chances over the coming 36hrs. Some reasonable totals are possible. There is also the chance of thunderstorms and hail.

Then note the next system coming through WA mid week, that moves southeast rather than east, being driven south by the strong upper high and northerly flow aloft. This is why less rainfall is being forecast across the nation. Moisture streaming through the nation is still there, but unable to be lifted into rainfall for SA. That seems to occur over southeast and eastern parts of the nation this weekend. Otherwise the tropics seeing a gradual increase in afternoon showers and storms and humidity before drying out this weekend again. Not much to come inland with a ridge suppressing rainfall at this time.

Euro 12z - Precipitable Water Values - next 10 days

Even though there is ample moisture, the systems coming through WA are out of phase with the moisture, being forced south. However there is a good supply of moisture being drawn in from the Indian Ocean, that is a good sign. It just struggles to link up with a trough and front hence why not much rainfall for SA. So we are back to the drawing board for Ag areas there I would think. For areas further east, heavier rainfall this weekend could see flooding renewed for southeast NSW and northeast VIC with topographic rainfall developing ahead of the front. Moisture retreats north of the nation over the tropics this weekend which is normal in the seasonal battle, bringing a brief reprieve to the build up conditions.

Euro 12z - Rainfall next 10 days

This is the driest out of all the models and you can compare to the GFS in my video with my analysis.

Simulated Satellite Picture - Saturday 18th September

Euro plants the cloud band today - note the decoupling of the moisture from the low diving southeast, while the trough and the moisture moves east through the eastern states, meaning less cloud, less rainfall, lighter falls.

Simulated Satellite Picture - Friday 17th September (this was the previous run from Saturday)

Euro on Saturday showing the moisture more in phase with the low passing through the Bight, and has a stronger system. This leads to more widespread rainfall and heavier rainfall thanks to better atmospheric dynamics.

A look at the medium term and searching for more of the wet stuff for areas screaming for some.