NATIONAL WEATHER PICTURE - PM EDITION - TUESDAY 20TH OF JULY 2021

Headlines


  • An active day of weather on both sides of the nation with the north and eastern inland remaining largely fine and unchanged from recent weeks of dry weather.

  • Showers with local hail and thunder continues for parts of the southeast with moderate falls over Central VIC and West Gippsland tonight.

  • Areas of light to moderate rainfall continues for areas along the GDR and points west in NSW with the rainfall easing overnight.

  • Snowfalls continue tonight and will ease before more heavy snowfalls develop this week.

  • Areas of moderate rainfall expected to sweep SA during Thursday before that sweeps into NSW and northern VIC on Thursday afternoon into Friday.

  • A wild weekend of windy wintry cold weather is expected for southeastern and southern Australia.

National Satellite Picture - Tuesday 20th of July 2021

An active satellite picture with large scale systems on both sides of the nation. Widespread rainfall is occurring in multiple states tonight and that should continue off and on over the coming week. The weather is essentially dry and fine over the northern two thirds with only high level clouds moving through the eastern inland with a ridge stifling rainfall.

Temperatures -Tuesday 20th of July 2021

You can cut the nation in 2, with the warm air being dammed over the northern and central inland areas thanks to the jet stream and fast flow pattern to the south being held in the same region by an upper high sinking south from the tropics into the central areas of the nation. This pattern is set to continue for the coming week at least.

A closer looks of numbers for the southern third of the nation, conditions have recovered nicely through parts of western NSW in clearer air between the systems.

Radar - Tuesday 20th of July 2021

Widespread rainfall across southern parts of the nation could bring moderate falls tonight to those areas west of the divide in NSW and about the southeast and central parts of VIC. Moderate rainfall moving much more efficiently from WA into western SA so rainfall could kick off earlier in the west of SA tomorrow and more rainfall for the west coast becoming heavier and more extensive with the low and front approaching.

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

Rainfall largely unchanged for most of the nation, with only the west seeing a slight drop in the rainfall expected considering some of it is falling right now. I have increased falls in western TAS and across the divide. But really the north dry and no change there in proceedings for the coming 10 days. The rainfall may build again into early August with the moisture increasing over the Indian Ocean and that will sit there waiting for the westerly wind belt to take a break.

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

Rainfall for the coming 2 weeks paints the picture that I explained in the climate update this afternoon with the north staying dry, most of the central inland dry and the southern third wet with the westerly winds increasing at times. Frontal weather to continue through to early August in line with the CURRENT guidance. Again notice the moisture sitting offshore the northwest coast of the nation ready to come in once the flow begins to behave and support inland rainfall. That is still possible through the outlook even though GFS is not showing it.

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

Rainfall is a little lighter tonight in the runs than what it had this morning, but GFS and Euro have swapped from this mornings run so the forecasts for mind are largely unchanged, with southern third wet, the northern two thirds of the inland largely fine, dry and warm to hot. Things may start to shift towards the end of the first week of August.

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

Rainfall looks to be winding down on the charts as we lose the systems from today but there is still follow up falls expected this week and into next week with a cold and blustery weekend for the southeast could produce more widespread wet weather than what is being advertised. There is some high amplitude weather to look at this week.


Model discussion and analysis


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

A wavy flow continues with more rainfall events to get through over the coming 10 days for southern Australia. For the north upper ridging and a high over the north to remain dominant so Groundhog day continues for the north. That is normal. The wintry flow will persist into the end of the month and likely to kick off August in line with climate drivers and model guidance. There are some absolute whopper frontal systems possible through southern Australia during the latter part of this month and to kick off August.

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

You can see the rainfall events over the coming 24hrs beginning to move east, the one out west to bring moderate rainfall to SA with that focus spreading further east into NSW Thursday and Friday. Then note the frontal weather this weekend with gales and showers and pretty cold air whipping through. A brief reprieve then more frontal weather and a big blast of cold air possible to end the month and kick off August. The north stays dry and warm with no rainfall expected.

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

The Euro is a little less robust compared to the GFS tonight but the models have basically swapped their positions from this morning, so the forecasts remain largely unchanged. Dry for the northern two thirds and wet and windy for the southern third of the nation. Next week, watch the large long wave trough that is building over WA, that does tap into moisture from the Indian Ocean again. See below on those details.

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

Moist airmass drifting through the nation is triggering light rainfall over multiple states tonight with frontal weather lifting that moisture. The moisture does get kicked out by a gusty southwest to southerly wind shift on Wednesday with a cold pool moving through the eastern inland into the Tasman. But it quickly returns from the west with a weakening low pressure system bringing more cloud and rainfall. The weekend cold and showery with the PW values again drying out. But watch next week, the next wave sitting off WA does get fed into the jet stream and the frontal weather will lift this into rainfall, despite modelling a bit slow on the uptake of that idea.

So there is more active weather to come in the next 10-20 days for southern Australia with the start of August also starting out wet and windy. The east and north dry and warmer under a ridge. Things will flip into August.

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