Victoria - Becoming hot with a thunder change: Dec 16-19

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Victoria - Becoming hot with a thunder change: Dec 16-19

Post by hillybilly » Fri Dec 15, 2017 7:24 am

Thread for the approaching event. Becoming warmer through the weekend (mid 20s south, mid 30s north) and hot generally for Monday and Tuesday. The uppers are extreme for this event (850Ts above 20C), with mid 40s forecast for parts of SA and NSW. Mildura forecast to hit 43C (which is a once every 5 years temperature for December there).

Further south cloud and some rain will cap things a bit. There is a big infeed of tropical moisture with precipitable water values around 50mm near the wind change. The dynamics aren't great, but current guidance suggests a fair bit of virga initially, then likely some showers and storms on Tuesday. Big split on the models with some giving dribbles and others locally heavy falls.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by StratoBendigo » Fri Dec 15, 2017 9:09 am

EC reckons 17mm here with the change on Tuesday night. Other forecast models aren't that interested.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by JasmineStorm » Fri Dec 15, 2017 11:08 am

Both EC and GFS keep locking in a late Tuesday afternoon squall line across central Victoria. I hope not but IMO, if this set up is correct, it looks like a classic late spring / early summer thunderstorm asthma scenario with the pollen propelled down into a cold outflow.
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Re: Becoming hot with a thunder change: Dec 16-19

Post by hillybilly » Sat Dec 16, 2017 7:41 am

Beaut day yesterday up here with a max of 23C. Looks similar here today.

Monday and Tuesday both stinkers, particularly in the north where places like Mildura will get well into the 40s.

Easterlies on Monday and then cloud on Tuesday should stop it getting too hot in Melbourne, but could still crack the old 100F mark.

Weak rain band entering western Vic early Tuesday and building to peak mid arvo on the trough. The trough sits just east of Melbourne when it goes bang. Typical scenario which could see us get between 2 and 32mm across the metro area. I'd be pretty hopeful of 20mm here, but these can really involve a bit of luck. There's a big tropical infeed, so this is a quite extraordinary airmass being very hot but also humid.

Thinking this one could well set records for high overnight minima. Monday night just looks crazy warm. Progs have into into the 30s and 1am in northern Vic, and in the mids 20s through the night. As for Max's, SA and NSW will see the peak, and definitely couldn't rule out some record highs in spots :?

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Re: Becoming hot with a thunder change: Dec 16-19

Post by hillybilly » Sun Dec 17, 2017 7:01 am

Progs wiggling on the front for Tuesday. They downgraded to almost zilch in the 12Z runs and now have mostly come back (except EC) on the 12Z.

Warm today, hot tomorrow. Easterlies and a bit of cloud will prevent it getting to hot in central areas tomorrow, but the west and northwest will bake. Stinker of a night Monday night.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by Tassiedave » Sun Dec 17, 2017 9:58 pm

Not much rain on the GFS raincast...

30 degrees forecast for Launceston and 31 for Hobart tomorrow.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by hillybilly » Mon Dec 18, 2017 6:53 am

First hot one across most of Vic, but cloud and sea breezes will take the edge off things in the south and east. Low 40s in the far northwest, and mid 40s across the borders in SA and NSW. Plenty of high level cloud and could well be the odd spit later as strong warm air advection kicks in aloft (this is the classic elevated summer warm front).

Double trough tomorrow. First (looks pre-frontal) comes through fairly early and looks mostly fine. Second comes through later associated with the the main front moving through central Vic mid arvo. Gusty winds and hot temperatures, but humidity stays ok.

Decent moisture infeed, which models are struggling with... jumping between moderate and minimal falls. Latest CMC and EC have near 20mm here, which ACCESS and GFS have about 5mm which highlights the range. Hopefully this one gives things a drink as it has dried off remarkably quickly (been quite a few small fires over the weekend around Vic which is remarkable after the month or two worth of rain we got at the start of the month for almost all of Vic).

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Re: Becoming hot with a thunder change: Dec 16-19

Post by stevco123 » Mon Dec 18, 2017 8:40 am

Ain't gonna be no 33 degree day. More like 26-27 I bet, maybe 30.

(Unless cloud clears)
Last edited by stevco123 on Mon Dec 18, 2017 2:24 pm, edited 2 times in total.
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Re: Becoming hot with a thunder change: Dec 16-19

Post by JasmineStorm » Mon Dec 18, 2017 10:46 am

High cloud, 28c here.

A very tough weather set up to read tomorrow. HB has done a very good job picking it apart.

I’ve had a good look on the latest EC run and I’m seeing humidity at the surface around 30% in central Victoria during tomorrow afternoon. This dry surface air looks like it’s going to be ingested into the atmosphere creating high based thunderstorms. Probably won’t see a lot of rain on the ground but its nasty for dry microbursts, dry lightning and trying to fly a plane. Thunderstorm asthma forecast has now been upgraded from low to Moderate for tomorrow, I’d be upgrading to high looking at the current models indicating a squall line. I’m thinking a nice shelfie should appear on the bay mid tomorrow afternoon as well :)

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Re: Becoming hot with a thunder change: Dec 16-19

Post by JasmineStorm » Mon Dec 18, 2017 1:26 pm

BoM now on board for tomorrow :lighting:
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Re: Becoming hot with a thunder change: Dec 16-19

Post by stevco123 » Mon Dec 18, 2017 2:24 pm

stevco123 wrote:
Mon Dec 18, 2017 8:40 am
Ain't gonna be no 33 degree day. More like 26-27 I bet, maybe 30.

(Unless cloud clears)


Fail for the above. I was wrong.

What time is the front due tomorrow?
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Re: Becoming hot with a thunder change: Dec 16-19

Post by Gordon » Mon Dec 18, 2017 2:42 pm

JasmineStorm wrote:
Mon Dec 18, 2017 1:26 pm
BoM now on board for tomorrow :lighting:
Impressive! Where can you access that chart JS?

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Re: Becoming hot with a thunder change: Dec 16-19

Post by JasmineStorm » Mon Dec 18, 2017 2:56 pm

Gordon wrote:
Mon Dec 18, 2017 2:42 pm
JasmineStorm wrote:
Mon Dec 18, 2017 1:26 pm
BoM now on board for tomorrow :lighting:
Impressive! Where can you access that chart JS?
It is an internal BoM chart they generate daily and recently they have started tweeting it publicly. It's not on the website to my knowledge. Here is today's tweet. https://twitter.com/BOM_Vic/status/942575221772619776

@Stevco - The first trough is a mid to late afternoon Melbourne special tomorrow... if it stays on track.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by Gordon » Mon Dec 18, 2017 3:33 pm

Thanks JS - fingers crossed for a direct hit!

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Re: Becoming hot with a thunder change: Dec 16-19

Post by Onetahuti » Mon Dec 18, 2017 4:23 pm

stevco123 wrote:
Mon Dec 18, 2017 2:24 pm
stevco123 wrote:
Mon Dec 18, 2017 8:40 am
Ain't gonna be no 33 degree day. More like 26-27 I bet, maybe 30.

(Unless cloud clears)


Fail for the above. I was wrong.

What time is the front due tomorrow?
You win some, you lose some. :-)

Max of 34.4°C according to my new Davis @ 3:00PM in your old stamping ground.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by hillybilly » Mon Dec 18, 2017 6:01 pm

Fail for the above. I was wrong.
I generally don't bet against the models when they are so consistent. ACCESS-R basically nailed it - 32-34C through most the metro area. The battle between the synoptic northeasterly, the hot uppers, and the sea breeze.

Northerlies will win out tonight, ahead of a two part change. Pre-frontal trough which dies, then proper wind change mid/late arvo. Progs pretty consistent now in showing 5-15mm with the change. Should be thundery so potential for some bigger falls (and also some lesser ones).

I would like 20mm please (to fill the tanks and water the garden :) ).

BTW some nasty heat back in SA. Multiple 47C in the north, and 46C at Port August. Plenty of spots getting within a degree or two of their December records. This will move into NSW tomorrow. Thankfull, staying north of Vic.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by JasmineStorm » Mon Dec 18, 2017 6:46 pm

1,500 km Australian bight squall line has generated around 10,000 CG's in the last hour.
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Re: Becoming hot with a thunder change: Dec 16-19

Post by typhoon29 » Mon Dec 18, 2017 8:08 pm

Looks like a classic stormy change for tomorrow, then again the whole thing could get blown to bits by the wind all just collapse as the last few have.
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Re: Becoming hot with a thunder change: Dec 16-19

Post by hillybilly » Mon Dec 18, 2017 9:04 pm

28C here in the end. Calm almost the whole day sandwiched between the northeasterly synoptic flow and the southeasterly sea breeze. Our DP briefly touched 17C which is getting high for here (and Moorabbin hit 19C). Definitely feeling the local really warm SSTs.

Btw that's an elevated warm front coming across Vic currently marking the onset of strong warm air advection. These often preceded our very hottest days (we had one on Ash Wednesday, Black Saturday and plenty of other nasty hot days). Thankfully, this surge of heat comes through overnight and gets pinched off by the approaching cold front and temperatures capped by the humdity and cloud. Further north it will be nasty heat, with 45C into southern NSW.

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Re: Becoming hot with a thunder change: Dec 16-19

Post by Australis(Shell3155) » Tue Dec 19, 2017 6:09 am

Can only see 0.2 @ Portland,
Is none of what is shown in radar touching the ground ?

Edit, tiny dots of moisture touching ground @ 6.30

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