NATIONAL WEATHER PICUTRE - EVENING EDITION TUESDAY MAY 11TH 2021.

HEADLINES


  • Heavy rainfall with ongoing flash flood risk for SE NSW and East Gippsland

  • Severe thunderstorms possible over the coming 24 hours for eastern QLD and NSW

  • Dry and warm in the west and north.

  • Showers to increase later this week over SE SA, VIC and TAS.


An active day of weather over the east with an upper low and trough combining with moisture and the cold unstable air to produce scattered showers and thunderstorms over eastern NSW and QLD. Heavy rainfall has developed over parts of Gippsland and South Coastal areas of NSW. Falls over 50mm have been received so far with more heavy rainfall ongoing.


Severe weather warnings are in force and for official warnings please visit the www.bom.gov.au for more details.


Satellite imagery - SE Australia showing the broad rotation with the upper low causing the unstable weather to it's south and east.


There is a significant thunderstorm risk still in place for tonight for large parts of eastern NSW and QLD with multiple rounds of severe thunderstorms possible as the low becomes near stationary over the Riverina. Wind fields and colder unstable air aloft will allow thunderstorms to develop as they did last night and continue into the morning hours.


Severe thunderstorms brought damaging winds and large hail to parts of the southern inland of QLD early this morning in the pre dawn hours.


Thunderstorm coverage on Tuesday afternoon in the random scattered pockets (yellow), near a trough (red) that is moving east through the Downs. A weak area of convergence inland over the Wide Bay are mainly showers. Valid 5pm EST

Conditions will remain unstable overnight and into Wednesday. The forecast for storms runs through until midnight Tuesday.


Thunderstorm Forecast for the rest of Tuesday May 11th 2021.

Thunderstorm Forecast for the rest of Tuesday May 11th 2021.

The unstable air remains in place during Wednesday with another round of strong to severe storms likely to redevelop, with the synoptic scale largely unchanged with the atmosphere able to produce robust convection. Severe thunderstorms are possible overnight.


Convective Available Potential Energy values for Wednesday 12th of May 2021.

The atmosphere is broadly unstable for the coming 24 hours over these regions, and multiple rounds of thunderstorms and showers are likely, until the trough moves offshore later Wednesday. An organised batch of thunderstorms could accompany this during Wednesday.


Thunderstorm Forecast for Wednesday - Valid May 12th 2021.

Thunderstorm Forecast for Wednesday - Valid Wednesday May 12th 2021.

Further details can be found on the severe weather event in Severe Weather Analysis.


The trough and upper low likely to lift out during Wednesday afternoon and evening, then offshore during Thursday morning, with conditions easing dramatically over the period. A front moving in from the west will also help to bump out the moist and warmer air, replacing it with cold drier air and week of below average temperatures for many locations.


Before then, we have got a risk of flash flooding and heavy rainfall leading to riverine flooding over the southeast of NSW and Gippsland overnight Tuesday through Wednesday, before conditions start to ease tomorrow night. Localised additional falls of 100-200mm possible in that region. Widespread 20-50mm surrounding this region from West Gippsland in Victoria to about Narooma in NSW.


Satellite over SE Australia showing the near stationary upper low and a trough throughout the southeast of NSW and eastern VIC bringing widespread rainfall. Valid 5pm EST May 11th 2021.


Flash flood forecast for Tuesday until midnight tonight - Valid 11th May 2021.


For now the remainder of the nation is relatively stable with high pressure anchored in over the west. The drier air is trapped over the west of the nation for now. The approaching cold front will have little impact on the region, with mostly high cloud and slight drop in temperatures. Perhaps a few showers for the SWLD, mainly south of Perth.


National Satellite imagery for Tuesday evening - 11th May 2021.


The pattern is expected to turn zonal this week, with that cold front over Perth, picking up steam and heading east into the southeast mainland, with the help of the consolidating high pressure, guiding it in in a westerly flow aloft. A band of rain and strong winds is likely to cross coastal areas of SA with light falls, more moderate falls into VIC and heavy falls of western Tasmania Thursday afternoon and evening.


Euro 00z run at 18000ft showing the flow pattern becoming zonal, absorbing the upper low in the east and conditions then being controlled by high pressure that takes over much of the mainland, keeping us all dry through the inland with rainfall extremely coastal beyond Sunday. Valid May 11th 2021.



A follow up front will come through on Saturday with much colder air, with showers increasing to rain again, mainly over southern VIC and western Tasmania with moderate falls. Following the rain, showers may turn wintry with local hail and thunder with strong wind squalls. Snow will develop down to 900m during Saturday.


The cold air will be drying out as it runs over terrain, so a bitterly cold but mostly dry day is expected for southern NSW with a brisk westerly flow. The dry cold airmass with winds going calm and the clear skies, the perfect recipe for severe frosts returning this weekend, with some areas seeing temperatures as low as -3C to -4C throughout elevated NSW.


The dry cold air will mean that the east coast will dry out for a good period after another wet and stormy start to the week, but also keep a large portion of inland Australia dry for the coming 10-14 days, with no large rainfall trigger in sight.


Euro 00z rainfall data - Next 10 days - Valid May 11th 2021.


GFS wants to kick off QLD rainfall again later in the month, but I do not buy that. I do think rainfall totals over WA will increase after this period, with a dry and warm spell coming to an end in around 9-10 days.


Weather Matters - Rainfall for the next 10 days. Valid May 11th 2021.


The temperatures will continue to be the big story with well below temperatures to continue for a good part of the next week, with overnights mainly to blame for that. The day times will be below average, but will gradually warm in the clear sunny skies, especially over the inland. Low cloud and drizzly skies will continue for the early part of next week over southern coast lines and won't clear until the high moves over the region later next week.


Warm weather to continue out west for the next week or so - with a warm and dry easterly winds to return later this week.


Colder weather to persist over the east with onshore southwest winds with that same slow moving high, controlling the nations weather beyond the upper low and cold fronts this weekend over the southeast.


Euro Temperature anomalies for the period until the 20th of May 2021.



A drier trend will develop from later this weekend, nationwide.


Want more weather details? Need more tailored information - then email me at karllijnders@weathermatters.org

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