NATIONAL WEATHER PICTURE - MORNING EDITION TUESDAY MAY 18TH 2021

Headlines


  • Cold and frosty start to Tuesday over the east and south.

  • Heavy showers and thunderstorms over the far southwest of WA.

  • The clouds and gloom hang on in the southern states

  • Pattern flip is on the horizon.

It has been a very cold night once again over large parts of eastern and southern Australia with temperatures well below average once again overnight with some centres getting down to -6C in southeast NSW. Canberra and the ACT generally recording minima as low as -5C.


Frost forecast Tuesday morning - verified very well across the east.



Things have warmed up steadily this morning where the fog hasn't formed, with a westerly wind regime continuing.


In WA, some locations recorded another 20-30mm overnight with slow moving showers and thunderstorms, this occurring south of Perth overnight. Isolated falls were close to 50mm in the region between Margaret River and Bunbury. Further showers and thunderstorms are possible today as the trough moves through.


The clouds and gloom continues to move through the southeast, with onshore southwest to southerly winds, bringing in low level moisture, to produce low stratus and drizzle patches to southern and mountain VIC and western TAS. With the air becoming more stable, the cloud cover will begin to thin out over the next 24hrs.


It has been a cold week for the east, while in the west, it has been well above average temperature wise, with that pattern continuing today and for the remainder of the week. The weather will flip over the weekend and early next week.


Satellite picture this morning shows once again a very clear satellite for the nation. A quiet morning nationally with no severe weather events unfolding, that is thanks to this stonking high pressure system that is continuing to meander through the southern states today.


Out west, a weakening pressure trough continues to kick of showers and thunderstorms along the west coast, with the falls, random, scattered and moderate. No severe weather is expected out across WA today with these thunderstorms.


National Satellite Picture - Tuesday 18th May 2021.

Over the southeast, after a cold start, as things began to warm up this morning, some localised areas of low cloud and fog has formed over the Snowy Mountains and adjacent regions, into the northern ACT as well, which has capped temperatures rising this morning.


Visible satellite showing the patches of fog over southeast Australia on Tuesday morning. Dry air keeping the remainder of NSW and QLD clear and sunny.

Overall the pattern is expected to remain slow moving with this high controlling the weather for next 4-5 days over much of the continent. So if you are living out west, despite the presence of more clouds than sun today, a warm airmass is in place and will stay there until the weekend.


In the east, cold and cloudy today and tomorrow over southern Australia, but clouds should begin to break up as the high moves eastwards during Thursday and Friday, with the clouds increasing along the east coast with showers developing, relocating the miserable gloomy weather away from, SA, VIC and TAS by the weekend.


Rainfall along the east coast north of Newcastle, mainly between 10-20mm with the wetter places through northern NSW maybe touching 30-35mm for the showery event. No severe weather is anticipated at this stage. Lighter falls of 5-10mm entering southeast QLD.


Upper Air Pattern at 18000ft showing the fast flow pattern developing towards the end of the period, with the warmer weather moving to the east and a cooler shift coming to the west. Rainfall chances do increase over southern Australia towards the end of the month. Euro 12z run valid Tuesday 18th May 2021.

The pattern begins to flip over the weekend, with a windy showery change developing for WA on Sunday, dropping temperatures by as much as 10 degrees and bringing 10-20mm of rainfall to the region. Follow up fronts will continue to bring periods of rain and gusty winds over the west coast.


During this time, the east will warm up with a northwest flow aloft bringing that warmer airmass from northwest Australia. Coupled with clear skies, it will be a good looking weekend for outdoor activities, not so great if you are a farmer and looking for some rainfall. Temperatures could reach 5-7 degrees above average by the end of the weekend into early next week through inland SA, western NSW and northwest VIC. Gusty winds may also bring areas of raised dust into the region.


Pattern Flip developing later in the weekend into early next week, with a high amplitude pattern establishing with a deep trough over the west and a strong upper high over the Tasman Sea. A warmer northwest flow aloft bringing temperatures up over the south and east. Euro 12z Valid Tuesday 18th 2021.


The east coast should also general clearance later in the weekend into early next week with a drier northwest to westerly flow developing as the high breaks down and then re-centres southeast of VIC.


By around the 25-26th of May, showers should redevelop for SA, VIC, NSW and TAS with a colder westerly shift. That frontal activity would have peaked already over the Great Australian Bight, but follow up systems do show more promise of bringing wetter weather and extending it further north over mainland Australia towards the end of the month.


Euro Rainfall next 10 days - Valid Tuesday 18th May 2021.

Further into the end of May and into early June, you can see evidence of that rainfall signal increasing for the southern half of the nation, with a series of cold fronts making impact for all southern states. This is in line with the SAM trending negative later this month into June. If this continues to extend into June, then it will be a wet start for southern parts of the nation, especially those areas exposed to a westerly wind regime.


Graziers should be advised that this could be a prolonged period of windy, cold and showery weather.


GFS Rainfall for the coming 2 weeks - Valid May 18th 2021.

There is a lack of moisture over vast parts of the nation at the moment, but this will be an area to watch as we end the month and move into June. There is evidence of moisture building up over inland WA and in the right area to be transported south and east via the jet stream into cold fronts, so more cloudiness is likely across the nation, but can it rain? We will wait and see.


Rainfall forecast - Next 10 days - Valid May 18th 2021.



Precipitable Water Values for the next 2 weeks - note the moisture values increasing over WA and northwest parts of the nation. Can it be picked up in phase with a cold front over southern Australia to bring widespread rainfall? GFS 18z Run - Valid Tuesday May 18th 2021.


Want more weather information for your part of the world? Email me at karllijnders@weathermatters.org to find out what I may be able to offer you.




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