NATIONAL WEATHER PICTURE - AM EDITION - TUESDAY 20TH OF JULY 2021.

Headlines


  • Significant shower and storm activity through the southeast state bringing some moderate to heavy rainfall.

  • A colder surge is expected to move north through the southeast inland today with showers developing for inland NSW.

  • Rain developing over WA this morning and increasing throughout the SWLD today before spreading further east.

  • Fine warm and sunny for QLD, but hot over the northern tropics with above average temperatures.


National Satellite Picture - Tuesday 20th of July 2021

The pair of cold fronts can be seen moving through the southeast this morning, and we can track that rain event moving through the southwest this morning with the main band of rainfall offshore with the front. Fine weather elsewhere, though cloud increasing over southern NSW is ahead of that front with conditions turning wet west of the divide today. Fine and clear over the north.

Temperatures -Tuesday 20th of July 2021

A seasonal morning for the nation, with temperatures near average in most places, a little warmer through SA with the cloud and showery burst and warmer over WA with that cloud and areas of rainfall. Clear and crisp over the eastern inland under a high pressure system. Fine weather over the north this morning with typical dry season conditions way from the extreme northern coastal areas where humidity is hanging on.

Radar - Tuesday 20th of July 2021

Front rolling into the southeast this morning brings widespread rain and shower along the axis this morning as it rolls northeast through the southeast states. Heavy falls near 80mm have been recorded in parts of SA with scattered falls up to 20mm. Windy and showery weather building through VIC and light rainfall over inland NSW will continue to increase today ahead of the front.

Rainfall has increased overnight over parts of the west coast and adjacent northern SWLD through the southern Gascoyne. 10-20mm has been observed so far with mainly dry conditions for Perth southwards so far, but the main rainfall is sitting offshore which will bring widespread falls to the entire SWLD this afternoon and this evening.

Rainfall for the next 10 days - Tuesday 20th of July 2021

I was hoping to change the chart more today with stronger data on the low pressure system and the weekend cold fronts for southeast Australia, but there has been little change in the synoptic so will wait to see what is happening after another 2 runs of the data before the evening updates. I have lifted to rainfall for parts of WA marginally, and obviously with the current pattern, no rainfall for northern Australia, maybe a few showers for the QLD coast, but few and far between.

00z GFS Rainfall for the next 10 days - Tuesday 20th of July 2021

Rainfall still largely unchanged from overnight data which again makes my life easier coming to forecast. Widespread showers over the southeast today with scattered moderate falls for SA and VIC, lighter falls into NSW. Good rainfall through the SWLD of WA today and into Wednesday will spread east into SA on Thursday before reaching the east on Friday. Frontal weather which follows the low over WA will bring windy and showery weather to the west and spread rapidly eastwards as we get to the weekend. More frontal weather developing next week for WA. The dry continues over the inland north of Coober Pedy to Giles.

00z Euro Rainfall for the next 10 days - Tuesday 20th of July 2021

Good agreement in the rainfall spread this morning throughout Australia, the wet weather continues for southern third of Australia with the westerly winds, dry over the northern half with changeable weather in the battle zone between the cold air and the hot air over the inland NSW through SA and into WA. The weather will remain largely unchanged through next week.

00z CMC Rainfall for the next 10 days - Tuesday 20th of July 2021

CMC is quite similar as per the other models this morning, with rainfall spread connected to the westerly wind regime and the north remaining dry for the coming 10 days. There may be some changes to the synoptic pattern as we get into August with inland rainfall developing.

Model discussion and analysis


00z GFS Upper Air Pattern and about 18000ft - Tuesday 20th of July 2021

The fast moving zonal flow is here to stay for the remainder of July and to kick off August so that means more of the same as to what we have seen across the nation during the past 10 days. The frontal weather passing through at times are strong with very cold airmasses involved with a few of these waves. The north remains dry under a ridge and upper ridging over the north of the nation will also bring up day time temperatures as the heat levels fluctuate with periods of more humid weather developing at times later in the period.

00z GFS Surface Pressure Pattern and Rainfall - Tuesday 20th of July 2021

A strong front moving through the southeast has offered an insight into those surprise rainfall totals with the high levels of PW in the air. The front moves northeast today, can see the rainfall already falling over WA today but the main rainfall is still sitting offshore, some areas have already recorded 20mm which again is much more than what the models were advertising. Further along, frontal weather races through the southern ocean, again the system on Friday into the weekend offers some chance of severe weather with damaging winds and heavy snowfalls for the southeast of the nation. More frontal weather next week may link up with some moisture over the inland of WA and rain fall could once again develop on the northern periphery of the long waves passing through southern Australia. Fine and dry for QLD and over the NT into northern WA.

00z Euro Surface Pressure Pattern and Rainfall - Tuesday 20th of July 2021

The Euro is very similar in it's spread this morning, with a significant front for the southeast and rainfall over the west. The low coming into SA this Thursday and Friday may bring moderate falls to parts of the EP, YP and through to the NSW/VIC border before weakening Friday and being absorbed into the northwest flow. Stronger fronts racing through WA bringing more rainfall will quickly pass to be in SA by late Friday and through the weekend with cold and showery weather developing over the southeast. Some chance of heavy snow and damaging winds once again. More fronts next week, a lot quicker to move east that the Euro so a windy, wet end to the month for southern Australia is a safe bet.

00z Euro Precipitable Water Values - Tuesday 20th of July 2021

PW Values are nearly 300% above normal through parts of WA hence the widespread rainfall, which could become heavy as the low rolls into the west this afternoon and tonight. Heavy falls are possible. Modest moisture values over the southeast has also lead to productive shower activity this morning along the cold front. The dry air continues for the north and east with the synoptic pattern keeping that dry air over the region under high pressure. Next week, note the moisture building once again over parts of WA, with the chance of rainfall redeveloping over inland areas, but the models will struggle to paint that with so much going on before then.

More weather updates to come today, with my Climate Outlook for August due by lunchtime.


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