NATIONAL WEATHER PICTURE - EVENING EDITION - MONDAY MAY 17TH 2021.

Headlines


  • Storms on the approach to southwest WA including Perth, this evening.

  • Severe frosts possible for southeast Australia Tuesday morning.

  • Warmer in the west and north, colder for the east and south.

  • Dry weather for most of inland Australia.

It has been a day of very little weather across the continent of Australia, with the only active weather on the approach to southwest WA near a trough and the potential for the below average daytime temperatures setting up an increased risk of severe frosts.


Nationally, the satellite shows the impact of that large high over parts of southern Australia. Most of northern and eastern Australia, sitting under that subsidence, experiencing sunny skies and light winds. The dry season also kicking into gear nicely over the Top End with Darwin having 18C overnight with inland areas getting down to 14C. That is cold and dry for May.


In the southeast, onshore winds rotating around the high and producing widespread low cloud, scattered light showers on and south of the divide in Victoria and western Tasmania this evening, they should clear out of SA overnight.


Inland areas are dry and clear with warmer than average weather out west and cooler than average weather out east.


National Satellite Picture - Valid Monday May 17th 2021.


The high pressure system no doubt is the dominating force as we track through this week. It is responsible for the well above average temperatures over the western and northern parts of the nation and colder weather over the southern and eastern sides of the nation. That leads us to then follow the warmth through the southern parts of the nation gradually moving east over the coming week, so a slow clearance and warming trend will continue.


But with the below average temperatures, we have frosts. Overnight we saw Glen Innes report -8C and many areas down to -4C with significant frost coverage. That will once again be in place with severe frosts, most likely over the southern end of the GDR but northern areas may even get some severe frost with the chance of temperatures well below -5C.


Frost Forecast for Tuesday morning - Valid May 17th 2021.



Finally some warmer weather on the horizon for the east - but it is a week away.... Euro 12z valid Monday May 17th 2021.

The flow pattern is expected to become more zonal as we track through the remainder of this month, meaning that the flat ridge of high pressure will propel easterly winds over the northern half of the country with a westerly wind regime to the south of the high. This current high is further north than the last meaning it will be rotated through via the winter westerly belt to the south, stopping a blocking pattern establishing. That also opens the door for more rainfall to develop for southern portions of the nation, in SA where they have missed out, it is good news.


GFS flow pattern for the coming 2 weeks, note the flow pattern becoming more wavy in the southern ocean, with frontal weather moving through at speed, with high pressure also running through that flow at a reasonable speed. This may open the door to better rainfall prospects from the end of the month into June. (Check out the latest climate post for further details). GFS 00z run for 500mb flow pattern (18000ft). Valid Monday May 17th 2021.


As a consequence of the slack weather pattern over southern Australia at the moment, rainfall will be coastal for the coming week with light falls expected for many areas. The wettest areas could be SWLD of WA and Western Tasmania in the prevailing westerly wind regime, given the northward track of the frontal belt over the coming period. Those falls then extending to mainland southern Australia later next week at the earliest.


Rainfall for the coming 2 weeks - GFS. The signals are there for rainfall to move northwards, but again these maps will change rapidly from run to run, make sure to look at these maps as a signal and not a foregone conclusion. Valid Monday May 17th 2021.

I am keeping rainfall strictly coastal for the next 7-10 days but the map will start to look different as we track into the weekend as we get better guidance on rainfall that will start to show up in short term guidance. So once again, we will see a shift towards that wetter signal later this week.


No change to the evening update on the national rainfall map for the coming 10 days, the persistence forecast remains in place with slow moving high pressure dominating. Rainfall for the next 10 days - Weather Matters.

So once again it is a bit of a persistence forecast this week, not much happening which is typical for this time of year. However things will start to become more dynamic at the end of the month into June with a negative SAM likely to bring up some windy showery and colder weather.


Need more tailored weather information? Email me at karllijnders@weathermatters.org to find out how I might be able to assist you.

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