MONDAY MORNING WEATHER - HEAVY RAINFALL CONTINUES OUT WEST, WARM OUT EAST, BUT WET ALONG THE COAST.

Updated: May 23

The weather is certainly quite volatile over the southwest of the nation, after severe storms last night, the weather quite nasty still for some areas today with squalls moving throughout the SWLD. A low-pressure system is expected to pass through quite close to the coast with that system once east, bringing much cooler air into the region.


Ahead of this front it is dry, breezy and mild to warm through eastern WA into much of SA with cloud increasing over much of these areas today, with a cloud band moving through the interior reaching the central parts of the nation. No rainfall is forecast at this time, with the bulk of the rain staying back in WA for now, that is thanks to the stable air with ridge in region.


A high in the east still slinging showers on the NSW and parts of the QLD coast bringing moderate falls, will persist until about mid-week, this is when the high begins to move away.


With the high moving east mid-week, it opens the door and allows the movement of frontal weather entering the Bight and into the southeast mid to late week with moderate rainfall possible along fronts and scattered light falls in between frontal boundaries, meaning that a few days of rainfall can expected for southern Ag areas of SA, through VIC and into southern NSW.


Temperatures are expected to be well above average for many areas ahead of this frontal boundary moving through mid-week, so that is still on the cards. The cooler than average weather will be moving into WA from today and that will spread to the remainder of southern and eastern Australia by the weekend and open the door for potentially quite cool weather to follow into early Winter.


As we move into the medium term, there may be further moisture infeed into the northwest and west of the nation, and it will be down to cold fronts timing themselves well with the fronts to see further rainfall spread across the nation. That remains to be seen though I am still leaning with more rainfall spreading across the country.


Let’s take a look

FORECAST

Rainfall Next 10 Days

Rainfall is forecast to continue over the southwest today, after some moderate to heavy falls overnight, that moderate rainfall will continue today with some heavy falls reserved for the western interior north of the Ag Areas. In the east, showers continue today in the onshore flow, most of the wet weather impacting NSW with moderate falls possible. Most of the rest of the nation is forecast to be dry with a high in full control. As we move into the middle of the week, this is where we see the rainfall spread across the nation, primarily for southern areas of SA, into the southeast inland with a low chance of a cloud band staying intact over the interior from WA, through the NT and into western QLD with light rainfall possible with the jet stream cloud. The bulk of the wet weather later next week will be found over the southeast inland and the southwest should turn dry for now, but I am still strapping a low confidence forecast on this, with further rainfall chances still likely as high moisture values run across northern and northwest Australia.

THUNDERSTORM FORECAST

Thunderstorm Forecast Monday

Thunderstorms from Sunday will continue into Monday over the eastern parts of WA before weakening and heading into the Bight during the afternoon and clearing. A low-pressure system passing close to the SWLD could bring damaging winds and gusty storms if it is close enough to the region. Some thunderstorms may reach the far west of SA during the evening. A few claps of thunder possible amongst the showers over the western interior of NSW and along the Central NSW Coast up to the Hunter.

Thunderstorm Forecast Tuesday

Thunderstorms are forecast to appear along a weakening trough and front moving through the Bight with potential for a strong wind gust and moderate rainfall. Thunderstorms could bring moderate rainfall to pockets of the Eyre Peninsula and thundery showers may reach the Adelaide region at night.

Thunderstorm Forecast Wednesday

Thunderstorms are forecast to develop once again over the eastern inland in advance of a trough that too, will bring scattered thunderstorms over SA with the chance of moderate rainfall. No severe weather is expected at this time.

Thunderstorm Forecast Thursday

A few isolated thunderstorms are possible about the southeast with a weak front pushing through. Possible thunderstorms over the northwest of WA with another surge of moisture moving through the jet stream.

Thunderstorm Forecast Friday

Cool stable air spreading through the nation leading to a very low risk of thunderstorms over all areas.

Damaging Winds Risk - Monday.

With a front rolling through during the end of the weekend, a period of strong to gale force winds is possible along the west and south coasts with some damaging wind gusts moving inland with the front rolling through. A small chance we could see storm force winds developing about the Capes with a low-pressure system rotating through closer to the coast during Monday before moving away.

Frost Risk Forecast - Monday to Tuesday

Light frost possible over a large area of southeast inland Australia with a large high keeping skies clear and winds light with that allowing temperatures to freely fall overnight. Frost mostly contained along the range in Victoria and possibly into the southeast of SA and over southern NSW.

MEDIUM TERM

May 29th-June 5th 2022

Rainfall Anomalies

We are seeing the bulk of the rainfall in the short term now coming through in the next week and then another event via a burst of moisture in the northwest flow running through the Indian Ocean, coming through with a large cloud band. The east coast, finally with a shift into a more westerly pattern, may see below average rainfall for this period which will be welcome for many. Near seasonal weather expectations most elsewhere, but watching that moisture over the northwest to see if that gets absorbed into the frontal weather passing through from west to east.

Temperature Anomalies

Not much change from yesterday for the medium-term outlook. The cooler signal will move through the south and to the east through the end of next week into the weekend with a cooler shift moving north through the eastern inland with a cooler southerly flow. The warmer weather is forecast to remain above normal over the tropics, but a gusty southeaster will arrive in the first week of June.

DRIVERS

SOUTHERN ANNULAR MODE - MAYBE A NEGATIVE PHASE DEVELOPING.

Could we be seeing the first prolonged negative phase in the SAM since last Winter? It is looking more likely which is a bit of a surprise to me given that the ENSO is still La Nina, but perhaps a sign that things are shifting in the Pacific which is bringing back the frontal weather via westerly winds. The east coast, may just be drying out.


DATA - Refer to video for more information and the model comparison and context about all the forecast products you see from me.


12Z Euro Surface Pressure Pattern and Rainfall Distribution - Next 10 Days

The weather is forecast to be fairly active in the west as mentioned throughout the weekend, the focus of the severe weather is there today and tomorrow while the east is beginning to wind down with showers about today with moderate falls expected. A few showers are forecast to remain over the east coast until mid week before conditions clear as the flow turns northerly. Now out west, the remains of a trough will move through SA as mentioned mid week with scattered showers and storms then the system will decay further over the southeast inland. Warm day will give way to a cooler westerly with showery weather increasing throughout the outlook period for the southern and southeast states. Drier weather spreading through the eastern inland for now but moisture running across the interior via the jet stream could spread rainfall from west to east, but that remains to be seen, however signals are increasing for that to take place during the weekend coming and into next week. Whether that moisture can be drawn into the frontal waves to the south remains to be seen as well. So, lots of interesting features to watch and the rainfall is coming back to areas that have missed out, and ceasing in areas that need a break.

12z Euro Precipitable Water Anomalies - Next 10 Days

Moisture is expected to linger from the east to northeasterly flow over the eastern and southeast. Out west, you can see a moisture bulldozer being drawn in via the jet stream and this is forecast to spread east along a series of cold fronts and this graphic below shows the shift from the easterly wind regime to the more traditional westerly wind regime with frontal weather becoming more dominant. The shift to Winter is near on schedule this year.


12z Euro Rainfall Accumulation - Next 10 days

Refer to video for more information

12z GFS Rainfall Accumulation - Next 10 days

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12z CMC Rainfall Accumulation - Next 10 days

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12z Euro Rainfall Accumulation - Next 15 days

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12z GFS Rainfall Accumulation - Next 16 days

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More coming up throughout the day including a look at the medium-term weather and state-based forecasts tonight.