MEDIUM TERM FORECAST - SPRING SEASON TRENDING WARMER NOW.

A shift over the coming week will shift the weather pattern after what has been a cool start to the season for much of the south and west of the nation. An upper ridge about to set up camp over SA and into western NSW to bring a period of drier weather with light winds and clear skies, temperatures allowed to move above the average in many locations away from the coastal areas.


The wet weather is biased over the eastern seaboard as discussed for the past 10 days, the seasonal easterly winds starting to return and we are seeing that impact the rainfall chances over the coming two weeks.


Over the north, the tropical easterly winds/trade winds are expected to deepen and shift further south during this window, allowing the wet weather, early onset rainfall to begin to shift south as well. This will eventually play out for widespread above average rainfall for much of the south and east of the nation into November.


Out in WA, an anomalous cold front with a broad reach throughout the state with widespread rainfall, that signifies the influence of the Indian Ocean for that part of the world. The IOD is in the process of peaking during the coming 2 weeks, so that will also play out into the coming 2-6 weeks across the nation as it wanes.


It may be dry in the coming period over inland areas of SA and through to western NSW and northern VIC under the upper ridge. This is very normal - and it is a chance to get stuff done before the next period of wet weather which will come. IF the temperatures go above average for a number of days during this outlook period, then there is a reasonable threat of even heavier rainfall to follow. The warmer the air, the more moisture the atmosphere can hold. This is something to watch moving forward.


Lets take a look.

Moisture Watch This Week - October 18-25 2021

Moisture is certainly caked in along coastal areas of the east, north and throughout the west with a major system coming in from the west. The values over the central inland of the nation and across portions of the eastern inland west of the divide, back to seasonal or below seasonal values under ridging holding back the rainfall chances for this period. The air will begin to turn more humid as we go through the outlook period into next week.

Moisture Watch Next Week - October 26-November 2 2021

Moisture is expected to sweep across the tropics and move south and west during this period. There is some chance that the moisture will be captured by the upper level westerly winds and also be lifted along a surface trough over WA and see showers and thunderstorms increase. If a heat low forms out of the trough and digs into the moisture then rainfall chances will come up for SA and the southeast states for the end of the month into early November. The east coast under onshore winds for a fair chunk of this time and a semi permeant trough over inland areas will see showers and storms form on and north/east of this feature as it oscillates around the region

Rainfall This Week - October 18-25 2021

Lean rainfall for inland areas of SA, western NSW and western QLD with the ridge. Rainfall is most widespread over WA and through the tropics as well as scattered pockets along the east coast with onshore winds and a series of short wave troughs passing through.

Rainfall Next Week - October 26-November 2 2021

The blocking pattern from the Tasman Sea should be resolved and the door will be opened for moisture to surge south and east from WA and NT with rainfall developing over the southern and eastern inland for the end of the month and into early November. Some of this could be rather heavy. Remember, we don't have rainfall every day to record average to above average rainfall. As we have seen in the past few months, one system can bring you all of your monthly rainfall in a sitting and that is the climate system we are currently working with.

Rainfall Anomalies - October 18-November 2 2021

Pockets of above average rainfall, especially for the west of the nation with this incoming system. The weather over the nation's north also supporting above average rainfall and with thunderstorms, the heavier storms will bring about heavy falls from time to time, with some locations doing very well and others sitting waiting for a decent drop. Storms lotto is in full swing.

Temperature Anomalies This Week - October 18-25 2021

The temperatures near seasonal for most of the nation, though pockets of the southwest and southeast could be cooler than normal with persistent cloud and rainfall opportunities. The onshore flow over the east leading to seasonal values with higher humidity. Over the north, heat levels are running very high this week with an upper high about.

Temperature Anomalies Next Week - October 26-November 2 2021

The nation should warm up over the end of the month, I think some areas through SA and VIC with western NSW could see the warmest weather so far this Spring. The east coast should remain seasonal for now. Over the north, with increased rainfall chances, the heat levels may come down and the cooler bias may persist for the west.

DATA - Refer to the video for more details at the top of the page.


18Z GFS Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

18z GFS Precipitable Water Anomalies - Next 16 Days

18z GFS Rainfall Accumulation - Next 16 days

12z CMC Rainfall Accumulation - Next 15 days

More details tonight in your state based forecasts. Maybe a little bit of a reprieve for some in the next week to dry out and get things ready for the busy run into Christmas.