NATIONAL WEATHER UPDATE - MORNING EDITION - FRIDAY 7TH MAY 2021

HEADLINES


  • Showers easing for the NSW coast today with the low weakening

  • Warm sunshine to continue for southeast Australia as high pressure rolls through

  • Rain breaking out over western SA with an upper trough

  • The dry season rolls on over the tropics.


Finally, the low pressure system over the Tasman Sea is beginning to wash out and weaken today, you may note the flow of showers over the NSW coast has begun to shift more into the south and the pace of the shower activity has begun to slow down. That indicates the system is on the way out and weakening with high pressure moving in.


Satellite imagery as of 10am EST Valid May 7th 2021.

Rainfall overnight has been extensive once again along the east coast, especially south of Sydney to about Merimbula and the adjacent inland with rainfall totals of 100-200mm once again observed in pockets along the coast.


Rainfall observed for the past 24hrs to 07 May 2021.



Minor flooding is occurring on the east coast along the Nepean and Shoalhaven Rivers, with peaks expected today, but the flooding should ease by Sunday.


GFS 500mb flow pattern showing the trough over the Great Australian Bight and the low in the east, in between, that weak ridge keeping things stable and dry for Friday.


We have high pressure beginning to move east through Victoria, it is a narrow ridge, however sufficient to keep conditions warm and dry with a northerly flow developing. A weakening trough is expected to bring high cloud through parts of the south and east this afternoon with little rainfall.


Next 2 weeks 500mb (18000ft) flow pattern showing once again the likelihood of cut off low pressure systems being the catalyst for rainfall over the east and south.


A weak cold front on the back side of this trough may bring a burst of showers through coastal areas on Saturday. Recent guidance has 1-5mm for much of SE SA extending through southern and mountain Victoria and perhaps 10mm for the west coast of Tasmania during Saturday.


A stronger system is expected to move through the southeast during Monday with a band of showers and strong winds, coming again for coastal areas of SA, perhaps extending some isolated falls into the Agricultural areas with light falls expected. The better rainfall will be through southern and mountain Victoria and western Tasmania. Isolated showers will penetrate north of the divide into Victoria but fall short of reaching southern NSW.


GFS and EC show a decent system towards the weekend, with a broad southwest flow aloft. This may open the door for a pool of cold air to be propelled through the south and east of the nation, with the potential for showers and thunderstorms to increase over inland NSW and QLD as we get to the end of the period. However confidence in this idea is not especially high.


Given that this system is still 10 days out, it is as signal at this time and nothing to get too excited about or pin any major decisions on.


Euro 12z rainfall accumulation for the next 10 days - Valid 07th May 2021 This particular run picks up on an upper trough linking into modest moisture over QLD producing rain and storms in about a week's time. That remains to be seen and will be monitored over coming days in future data sets.


For SA, we have inland rainfall developing today with an upper trough moving into the west of the state, linking into modest moisture that has been drawn southeast via the jet stream from the Indian Ocean.


Areas of rain, with one or two thunderstorms have been observed in parts of WA over the last 24 hours with some moderate falls. That rainfall is heading east and southeast today.


Satellite imagery for SA - Valid at 10am CST May 7th 2021


The rainfall is expected to be patchy with some areas receiving 10-20mm while the majority will struggle to get towards 5mm. The air is not especially unstable and with a lack of dynamic forcing, rainfall will not be widespread and or heavy.


Relative humidity as of Friday afternoon with modest values coming into the west of South Australia, so with the upper trough, rain will break out through the region and spread east through central areas overnight and into Saturday morning.

Rainfall for the next couple of days over eastern SA as forecast on May 6th 2021. The forecast is largely unchanged on current guidance.

The rain will clear east over the weekend and dry warm weather is set to develop next week over WA and SA with a large high moving in and strengthening further as we get into the next week, so temperatures are expected to move well above the average over WA and western SA in response to this high pressure system.


Euro 500mb chart showing the upper high moving into the SWLD pushing the long wave trough and wet weather to the southeast of the nation bringing the colder weather out east and warmer weather back to the west for next week.

Temperature anomalies for next week into the weekend, showing that colder surge over the southeast eventually being spread through to central and northern Australia via southeast winds as the high ridges into the Great Australian Bight.

That will lead to a good shot of dry air and cooler weather developing once again in about a week's time over the northern parts of Australia. Darwin and surrounding communities and indeed communities down the Stuart Highway will have much cooler nights, tending colder south of Tennant Creek with frost possible about the outback.


Daytime temperatures will also see a reduction in temperatures and stronger east to southeast flow pushing out the seabreeze over northern coastal areas, leading to cooler nights, especially away from the coast. Some inland areas of Darwin, in the rural area, could see overnights drop to 15C from next weekend.


Overnight minimums next weekend - starting to feel the impacts of the colder bursts working through the southeastern parts of the country, rotating up on the periphery of high pressure. Euro 12z Model run on Temperatures next Saturday night 15th May.

Daytime temperatures Euro 12z run for May 16th 2021 showing the flush of milder weather coming up from the southeast pushing the heat to the extreme far northern coastline. Drier air at the surface will make the day time temperatures feel less than 27C for most of the region.


Conditions looking fairly benign and seasonal through the nation over the coming week or so. With a lack of major severe weather evets in the outlook. many areas will get a chance to dry out, and many farmers can prepare for the next lot of rainfall coming up in late May, in line with the overall medium term trends.


Another update coming up this evening.


If you want more tailored weather forecasts - email me at karllijnders@weathermatters.org to discuss your options.


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