VIC - Low pressure sequence. 24–31 May 2019

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JasmineStorm
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VIC - Low pressure sequence. 24–31 May 2019

Post by JasmineStorm » Tue May 21, 2019 11:47 am

Time to pull the trigger as May might go out with a bang. A sudden stratospheric warming event over the South Pole between 10 to 12 May, has propagated into the troposphere, sending the polar jet stream northward. This is setting up a sequence of upper polar lows that will become stronger in the sequence with a penetrating Rossby wave, pushing fronts, troughs and potentially creating a surface cut off low in a week from now.

Some of the projections from main EC and the new GFS version in the last 2 runs for next week are totally wild, which generally means downgrades are to come…..but if they verify, this would see a May cold snap around the 28th to 30th into SE Australia not experienced since the turn of the century, May 2000.

Let the ride begin :)
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GEFS EC ensemble.jpg
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SSW May 2019.jpg
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Re: Low pressure sequence. 24–31 May

Post by JasmineStorm » Tue May 21, 2019 5:37 pm

Latest runs across the board still showing a strong sequence, New GFS has a brutal polar cold shot at the end with -5c @850 hPa across Vic. Rainfall wise, 20 to 100mm across a wide area (especially southern) for the last week of May. EC control dropping the cut off low scenario but keeping a big SW flow next week. Latest BoM MSLP showing the frontal boundaries below Africa at the moment.
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hillybilly
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Re: Low pressure sequence. 24–31 May

Post by hillybilly » Tue May 21, 2019 6:27 pm

Am liking the latest set of progs :D I was fearing another below average month, but if EC verifies we may well get above average. Wild, windy and wet. Just like it should be as we approach winter :D

Couple of mild partly cloudy days before it starts to impact us.

Bit nervous about the potential for a significant storm surge and recession event. Vic's beaches have been hammered as the sea level trend pushes those beaches back with "each storm" :?

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Re: Low pressure sequence. 24–31 May

Post by Didjman » Tue May 21, 2019 8:09 pm

JasmineStorm wrote:
Tue May 21, 2019 11:47 am
Time to pull the trigger as May might go out with a bang. A sudden stratospheric warming event over the South Pole between 10 to 12 May, has propagated into the troposphere, sending the polar jet stream northward.

Let the ride begin :)
What causes this sudden warming in the stratosphere? Coronal Mass Ejections or more local influences?

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hillybilly
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Re: Low pressure sequence. 24–31 May

Post by hillybilly » Wed May 22, 2019 6:33 am

Didjman wrote:
Tue May 21, 2019 8:09 pm
JasmineStorm wrote:
Tue May 21, 2019 11:47 am
Time to pull the trigger as May might go out with a bang. A sudden stratospheric warming event over the South Pole between 10 to 12 May, has propagated into the troposphere, sending the polar jet stream northward.

Let the ride begin :)
What causes this sudden warming in the stratosphere? Coronal Mass Ejections or more local influences?
All internal to the atmosphere. They are triggered/associated with the polar front/jet waving which throws polar air north and warm air south. Basically the weather goes from being zonal where things are zipping around the pole like a donut to high amplitude waves. You can see this in the Southern Annular Mode (SAM) which is about to go negative for the first time in months (see seven day forecast at https://www.cpc.ncep.noaa.gov/products/ ... _mrf.shtml).

The SAM positive values explain the terribly dry conditions across southern Australia.

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Re: Low pressure sequence. 24–31 May

Post by hillybilly » Wed May 22, 2019 6:36 am

Progs look to be holding. Widespread 20-100mm fall in southern and mountain areas. Big falls about South Gippsland, Otways, Yarra Ranges. Will be wild on the coast with gales for a week. Big surge and wave event.

Potential for a significant snow event. 850Ts drop below -4C around Wednesday next week with snow levels down below 800m. Currently EC suggests potential flurries about the tops of the Dandenongs :D

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Re: Low pressure sequence. 24–31 May

Post by JasmineStorm » Wed May 22, 2019 6:39 am

just adding the HB's comments...

The sudden warming is caused by upward propagating tropospheric zonal winds becoming weak, allowing the stratosphere to warm. Once the zonal winds pick up again, the Stratosphere and Troposphere start to couple, which has a weakening effect on the tropospheric polar vortex, in turn sending the polar jet stream north into the mid latitudes. An event like this also occurred last May (2018) which dropped snow to around 500m near Ballarat.

Yes, latest EC run looks cold and wet. A top of 4c next Wednesday for here and Melbourne not above 12c for 3 days :)

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Re: Low pressure sequence. 24–31 May

Post by stevco123 » Wed May 22, 2019 8:54 am

Ah yes... May 2000. That was a great event. 2 days of almost non stop rain/ drizzle (including long lasting graupel showers), and snow on mount Dandenong.

Melbourne had a maximum if 10 or 11 for about 3 or 4 days straight then. I'm prompted to go back to my newspaper clippings (those were the days before mainstream internet believe it or not)
https://www.weatherlink.com/bulletin/53 ... 76dd68e8bc: for current weather updated every 2 minutes

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Re: Low pressure sequence. 24–31 May

Post by StratoBendigo » Wed May 22, 2019 10:12 am

stevco123 wrote:
Wed May 22, 2019 8:54 am
Ah yes... May 2000. That was a great event. 2 days of almost non stop rain/ drizzle (including long lasting graupel showers), and snow on mount Dandenong.

Melbourne had a maximum if 10 or 11 for about 3 or 4 days straight then. I'm prompted to go back to my newspaper clippings (those were the days before mainstream internet believe it or not)
There was so much that was epic about that event. 1 metre of snow falling on Lake Mountain in the last week of May. Settled snow in the Dandenongs and Central Highlands. Snow reported falling as low as 200m above sea level in the Western District....

The other epic May cold outbreak was 1970.

This coming event won't quite be as dramatic as those, but there's a good chance it may kick-start the snow season for 2019.

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Re: Low pressure sequence. 24–31 May

Post by Sean » Wed May 22, 2019 12:24 pm

Hoping that May finishes with a bang.. I'm ready for a proper cold outbreak.

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Re: Low pressure sequence. 24–31 May

Post by hillybilly » Wed May 22, 2019 5:42 pm

Latest EC is a ripper. Lots of rain. Then a huge cold outbreak that would give snow showers from Ballarat to the Queensland border ranges. Be interesting to see if it holds. Cracking frost following it :o

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Re: Low pressure sequence. 24–31 May

Post by Didjman » Wed May 22, 2019 6:01 pm

Signs are there for maybe another smaller cold outbreak around June 5 - 9

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Re: Low pressure sequence. 24–31 May

Post by flyfisher » Thu May 23, 2019 10:05 am

The IOD looks shockingly bad. These SAM events are great, imagine what they could do with a proper tropical infeed.

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Re: Low pressure sequence. 24–31 May

Post by StratoBendigo » Thu May 23, 2019 2:28 pm

A bit of a heatwave today, especially in NW Vic. Walpeup on 26.9c so far. (It did get to 27.4c at Ouyen on May 26, 2014).

23.3c at Yarram is notable too.

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Re: Low pressure sequence. 24–31 May

Post by Sean » Thu May 23, 2019 3:22 pm

I spot a 13c in the forecast :D

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Re: Low pressure sequence. 24–31 May

Post by Skywalker » Thu May 23, 2019 4:43 pm

Sean wrote:
Thu May 23, 2019 3:22 pm
I spot a 13c in the forecast :D
That's still crap, I want single digit maximum's! :bringiton: ;)
Caroline Springs, Melbourne's meteorological boredom zone.

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Re: Low pressure sequence. 24–31 May

Post by hillybilly » Thu May 23, 2019 8:09 pm

StratoBendigo wrote:
Thu May 23, 2019 2:28 pm
A bit of a heatwave today, especially in NW Vic. Walpeup on 26.9c so far. (It did get to 27.4c at Ouyen on May 26, 2014).

23.3c at Yarram is notable too.
Definitely not normal late May weather :( Just missed the Vic late season record of 27.5 at Mildura on 24/5/1994.

Few showers in bound, so odd sprinkle overnight. First proper rain still not due til late Saturday.

Next week looks wild. EC got about 60mm here which will get us past average for the first time this year, and over 100mm at the house in Walkerville. Not quite as cold, so snow mainly in the alps.

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Re: Low pressure sequence. 24–31 May

Post by Gordon » Thu May 23, 2019 9:49 pm

First sprinkles here; looking forward to a week of rain days (can we crack 200mm for May?) but not so much the cold and wind.
Last edited by Gordon on Thu May 30, 2019 7:44 am, edited 2 times in total.

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Re: Low pressure sequence. 24–31 May

Post by JasmineStorm » Fri May 24, 2019 8:41 am

Nice and dark to my west.

The Adelaide and Melbourne airport's weather balloons recorded 'total totals' of 51 and 50 this morning. It's quite unstable aloft, so any mid level moisture near the incoming trough might produce a rumble or 2 today and this evening.

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Re: Low pressure sequence. 24–31 May

Post by Macedonian » Fri May 24, 2019 9:20 am

I cant imagine that we will ever return to normal winter weather.
Raining here this morning. Just started about 20minutes ago.

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