QLD - UNSEASONAL RAINFALL WITH THE CHANCE OF FLOODING DEVELOPING FOR SOME AREAS IN THE DAYS AHEAD.

OVERVIEW

The rain event has commenced today, and the coverage of rainfall is forecast to increase overnight and into Friday with moderate to heavy falls likely to emerge by dawn. The rainfall is expected to extend to the coast and southeast during Friday and slowly contract out of the northwest in the coming 2 days.


Then the rain and storms look to stick around through the weekend and into early next week with the severe weather potential ongoing for parts of the coast as the upper trough deepens once again.


The far west should be dry by early next week.


SHORT TERM

So it is all about this large scale rain event with the flooding potential and severe weather issues throughout coastal areas down to the Sunshine Coast and extending back inland towards Mount Isa. The rainfall is expected to increase further across the east during Sunday and early next week with severe weather issues continuing with the passage of the trough before conditions ease Wednesday.


From that point on, the weather should return to dry, settled and sunny conditions with high pressure ridging through and the flow pattern tending westerly again.


LONG TERM

The east coast block is expected to move out by later next week and frontal weather which should be glancing through the southwest of the nation. That frontal weather will begin to track eastwards through the end of next week with stronger systems launching through WA then these look more likely to come across Southern Australia with more intensity as we track into the second week of July.


So once we lose the extensive rainfall over the north and east of the country, the weather is expected to return to more traditional conditions. Whether it can overcome the rainfall deficits over southern and Western Australia will be the question but right now it is unlikely.


AREAS TO WATCH

The SAM phase is important to watch over the coming week, if we see it head back into a negative phase then the frontal weather coming through in the second week of July could be very productive given the location of the wave action over the Southern Ocean.


The Indian Ocean is forecast to remain warmer than normal and this will feed moisture into the jet stream, whether it does it with the next wave of active frontal periods in the first part of July will be the issue, but most climate models support above average rainfall for July.


WEATHER VIDEO PM - THURSDAY 30TH JUNE 2022

FORECAST

Rainfall Next 10 Days

Widespread rainfall is expected to continue over the interior from Mount Isa through to the SE QLD Coast with the bulk of the heavy rainfall forecast to be near and north of trough over the interior Friday and along the coast Saturday through Monday but possibly into Tuesday before easing and clearing mid next week. Some areas could see 200-300mm of rainfall from this event but possibly more about the exposed coast between Mackay and Hervey Bay. Up to 100mm for a few centres over the interior as well. Flooding is of concern in these areas, both riverine and flash flooding. The showers decrease mid next week with high pressure coming in.

Rainfall through the interior is of significance for this time of year but more importantly along the coast, rainfall of that nature in the dry season and the cooler season is about a 1/50-year episode, we have to go back to 1973 to see something similar to this occurring. So very anomalous weather, do not expect the modelling to handle it well as the interval of this type of weather occurring is quite rare.

Rainfall back over the northern parts of QLD and into the NT is about a 1/25 year event, Darwin seeing it's coolest and wettest dry season spell in about 15 years so far and not getting above 30C for a while gives you a sense of the scale of influence the warmer waters north of Australia will have on the weather for the state moving into late Winter and into Spring and Severe Weather Season.

SEVERE WEATHER WATCH - QLD

The risk zone for severe weather is unchanged from overnight with the trough over the interior driving up the chance of moderate to heavy rainfall and the coverage of that heavy rainfall could see riverine flooding develop. Also with the high rainfall rates, flash flooding is also a risk. The risk of riverine flooding is highest along the QLD coast from the Mackay region southwards to about the Sunshine Coast at this time. The focus of the riverine flooding builds later in the weekend into early next week along the coast.

RIVERINE FLOOD RISK - QLD

A low risk of riverine flooding for the inland and a moderate to high chance along some of the coastal catchments in response to heavy rainfall developing near a stationary trough from the weekend and into next week.

FLASH FLOOD RISK - QLD

Pockets of heavy rainfall is expected to feature along a sharp surface trough combining with deep moisture and this is leading to widespread rain but embedded in that will be some heavier convection leading to those locally intense rainfall rates. A moderate to high risk of this unfolding throughout the interior during Friday through Saturday and along the coast from Saturday through Tuesday. Clearance of the severe weather risk dependent on the movement of the trough to the east which remains up for debate looking at modelling this morning.

MEDIUM TERM

July 8th - July 15th, 2022

Rainfall Anomalies

Relatively seasonal conditions forecast across most of the nation, though there are some increasing signals on the modelling, some quite aggressive, for rainfall being above average over the southeast and south of the country and possibly about the southwest. I would like to see more modelling on board for the higher rainfall chances to be extended into SA and NSW but right now I am not convinced of it.

Temperature Anomalies

There has been a shift towards a cooler bias across the nation in recent days and while I am seeing that colder bias, I am not confident on it being as cold as models suggest so keeping things milder over the east and southeast, cooler over the north and northwest and across western parts of the nation.

DATA - Refer to the video for further information.


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

As mentioned, there is so much going on in this active pattern and to cut down reading time, refer to the video at the top of the page.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture levels remain excessive along the east coast with some very heavy rainfall totals to develop for this time of year in response to that. The deeper moisture moving out of the NT, through QLD and into NSW and then remaining along the east coast, which is representative of the positive SAM phase. Overall, the pattern will breakdown mid next week, meaning that conditions along the west coast and through southern Australia will remain dry and settled under high pressure. Moisture will overcome the drier airmass over in the west by the end of next week, that moisture then spreading along the southern coastal areas bringing up the chances of rainfall for southern Australia once again and drier air moving back over the eastern and northern parts of the nation.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - a 1/50-year event is likely to unfold in the coming days over northern and eastern QLD with some locations seeing significant risks of flash flooding and riverine flooding. The upper low responsible won't move away until about this time next week which will lead to rain sticking around for a decent chunk of the week. Drier weather resumes once we see westerly winds return.

More coming up from 8pm EST with a look at the models and rainfall.

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