MEDIUM TERM FORECAST - MULTIPLE WEATHER EVENTS ON THE BOARD OVER THE COMING 2 WEEKS.

As we have a large scale multi day severe weather event unfolding across the south and east, we have further severe weather that needs to be discussed, especially over in the west in the short term. There will be a lot of focus on what happens out east today with good reason, but our friends in the west, you need to prepare for a severe weather event from Monday.


A strong surface low and associated cold front and trough is expected to ram through the SWLD with significant wind and heavy rainfall and thunderstorms from Monday into Tuesday. Locally heavy falls and damaging winds could cause some issue for crops in the SWLD, given how wet it has been and this could be 1-2 months rainfall for some locations.


The front and trough will then move across the southern coastline of Australia with a deep moisture plume being dragged southeast through to SA, VIC and southern NSW. That will introduce a warmer airmass initially after this colder week, which will be nice, but the air will turn unstable with showers and storms developing from this time next week. No real guide as to whether this is a severe storm outbreak at this time.


In the east, onshore winds rotating around a large high over the southeast is expected to bring showery humid air into the region. This will promote moderate falls for coastal QLD and NSW with thunderstorms developing on and east of the divide from Monday through mid week. Some of those storms could be heavy with flash flooding.


The tropics, hello to you - weather remaining soupy and foul with scattered showers and thunderstorms.


Lets take a look

FORECAST CHARTS

Moisture Watch This Week

No change in the guidance as per the video - we have good agreement in the modelling in terms of moisture placement. The issue is where the systems peak, whether the blocking pattern in the east forces the moisture south through the Bight or is weak enough to bring the moisture through this time next week with rainfall increasing. The tropics getting active again this weekend and again mid to late next week.

Moisture Watch Next Week

No change in the pattern in the medium term with the moisture continuing to stream in from the Indian Ocean with troughs over the inland allowing for showers and storms to increase once again. A positive SAM phase also keeping the east wet at this time. A stalled trough over the inland of QLD through to VIC could bring further rainfall and keep the moisture in place, trapped by the block over the Tasman.

Rainfall This Week - October 14-21 2021

A lot of rain ongoing today through Saturday over the southeast, another burst of rainfall as mentioned over the southwest will prove to be tricky for farmers out west with the risk of heavy falls and the tropics and through the east of QLD and into NSW humid with onshore easterly winds promoting more showers and storms. A trough over the east may form into another low pressure system just offshore with widespread showers and thunderstorms.

Rainfall Next Week - October 22-29 2021

A trough over inland QLD through to VIC may keep the showers and thunderstorm chances going during this period with a humid easterly dip scenario. The moisture may help to prop up a trough coming into SA with showers and thunderstorms about as well. Moisture still expected to sweep down the Stuart Highway from the NT into the eastern states lifting rainfall chances. The west cool and dry under stable ridging.

Rainfall Anomalies

This is now reflecting the negative IOD phase with above average rainfall not only ongoing for some parts today but likely to expand again over western areas of the nation with an anomalous weather even causing severe weather issues there and above average rainfall. Then we focus on the east coast simultaneously with an east coast trough and heavy showers and thunderstorms about for the first half of next week. The medium term offers an active tropical setup, that moisture then streaming southeast into the eastern Australia, especially QLD, NSW and VIC. A trough stalling out could produce showers and thunderstorms for a number of days through this period and I have not drawn in the rainfall potential in terms of low pressure systems but this chart could turn heavily green over the east in coming days. SA should see some on and off rainfall but the bias is still north and east.

Temperature Anomalies This Week

Colder over the southeast today and through the weekend, with the rainfall it has been cold through much of VIC and NSW. The weather starting to warm up from the weekend as the air modifies and the skies clear. The west is warm for the coming days but early next week, the weather is expected to turn colder and blustery. The north may see a reduction in heat levels but still above average for this period.

Temperature Anomalies Next Week

The heat that was being progged to come southeast looks likely to be held back over the central and northern interior as the pattern shifts into an easterly flow. That is thanks to a positive SAM. The east may see seasonal to below seasonal values and the southwest is colder than normal under persistent ridging.

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


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

18z GFS Precipitable Water Anomalies - Next 16 Days

18z GFS Ensemble Rainfall Accumulation - Next 16 days

12z CMC Rainfall Accumulation - Next 15 days

More details coming up in the medium term in the state based forecasts tonight. Again I will be looking closely at severe weather trends this afternoon. Stay weather aware in the east and southeast. Over in the west, enjoy the sunshine for now!!




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