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#1479762 - 13/12/2018 07:11 SA Cut off low, windy showers/rain poss small hail Dec 13th-15th
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14984
Loc: Seaford Meadows, SA
This really needs a thread and will be one of the more significant weather events of the year, possibly second or third behind the nasty wind we had in late November.

A strong upper trough has moved up from the SW and is in the process of interacting with a broad trough further east where warmer, moist air is flowing S/SE'ward. A baroclinic leaf is already forming beneath the axis of the upper trough where cyclogenesis of a deep surface low is beginning. Further west a strong high is trying to move in but the deepening of the sfc low will really crank up a strong LLJ (low level jet) on the western flank of the low creating very windy conditions across SA, especially southern coastlines, the gulf waters/coastlines and the Lower SE coastline as well as elevated terrains chiefly with a southern exposure.

The worst wind will be later tonight right through till at least late morning tomorrow as the low slowly tracks north across western VIC into SW NSW.

Now as the upper low intensifies across N VIC the sfc low will retrograde and then eventually become vertically stacked as one whole powerful system, wrapping humid tropical air in from the N and even warm, moist Tasman Sea air from the east. Areas of rain and isolated thunderstorms over VIC especially, heavy at times, then wrapping back up and around the base of the low and into the LSE of SA, extending north and NNW later today and overnight into tomorrow. The main focus for SA rain will be over the Murraylands, Upper SE, Lower SE and also the southern and SE exposed faces of the Mt.Lofty Ranges/Fleurieu Peninsula where fairly rare reverse orographics will be at play giving areas that are normally strongly rain shadowed a good drop in a strong S/SSE flow. Places such as Strathalbyn, Murray Bridge, Callington, Mt. Barker, Finniss etc etc should do fairly well, and right out across past Tailem Bend, Karoonda and Bordertown will see decent falls.

Adelaide itself will see very windy conditions but will be rain shadowed to a degree from the best rainfall potential...however eventually the main wrap around should move in overnight tonight with showers increasing possibly to rain more likely about the ranges, far southern suburbs and eastern slopes where the best falls will be. Good falls are also likely up into the Mid North about Melrose etc.

Overall, a very dynamic and powerful cut off low for December wrapping a deeper flow of moisture around it than usual, certainly excellent falls over VIC and parts of NSW and in eastern SA where places usually miss out.

Rainfalls generally 25-40mm across the Murraylands and USE, LSE, 10-20mm across Adelaide, isol 25mm in far south decreasing to 5-10mm further north and about the coast...8-15mm over the Mid North with isolated 20-40mm falls. The back of the Mt.Lofty Ranges and parts of the elevated Fleurieu Peninsula has potential to see 50-75mm falls.

So batten down the hatches, this wind will be relentless and catch a few people by surprise I think.

TS cool


Edited by Thunderstruck (13/12/2018 07:14)

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#1479776 - 13/12/2018 08:29 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Werner K Offline
Weather Freak

Registered: 28/11/2011
Posts: 534
Loc: Flinders Park, SA
Thanks for the detailed write up, Lennie.

Hoping my property at Ponde finally gets a decent drink as a lot of my plants are screaming for water after a very dry winter with only about 70mm between April & October. Had a reasonable October/November though with ca 30mm.

Had 2.3mm at home until 715am to start proceedings off.


Edited by Werner K (13/12/2018 08:31)
Edit Reason: spelling, extra info

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#1479781 - 13/12/2018 08:42 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
willitrainagain Offline
Weather Freak

Registered: 13/12/2011
Posts: 591
Loc: Mt Barker S.A.
Thanks T.S, very comprehensive

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#1479801 - 13/12/2018 10:04 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
*jr* Offline
Weather Freak

Registered: 06/01/2011
Posts: 104
Fairly dramatic seas down Victor harbor way peaking around midday Friday. Metropolitan waters less so with the southerly direction of the event.

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#1479974 - 13/12/2018 18:25 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Markus Offline
Weatherzone Moderator

Registered: 02/12/2010
Posts: 2239
Loc: Clare, SA
7.5mm so far, most of that in a quick, very heavy shower around midday with a fair amount of small hail too.
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#1479990 - 13/12/2018 18:42 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
betsuin Offline
Weather Freak

Registered: 07/04/2010
Posts: 759
Loc: Magill, Adelaide
As above great write up TS! Thanks!
5mm here so far.

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#1480142 - 13/12/2018 23:11 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
StormCapture Offline
Weatherzone Addict

Registered: 19/12/2013
Posts: 1703
Loc: Uleybury
15.8mm so far at home, quite surprised but did get a few heavy showers.

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#1480154 - 14/12/2018 00:19 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Eevo Offline
Weatherzone Addict

Registered: 02/11/2013
Posts: 1681
Loc: Bridgewater
10mm since midnight.

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#1480178 - 14/12/2018 06:16 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
roves Offline
Weatherzone Addict

Registered: 02/02/2005
Posts: 1636
Loc: Paringa-Riverland
OMG woke up to find 30mm in gauge this morning on top of 12mm yesterday, its a bit wet here.
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#1480226 - 14/12/2018 09:03 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Werner K Offline
Weather Freak

Registered: 28/11/2011
Posts: 534
Loc: Flinders Park, SA
Received 5.4mm until 730am.

Have seen that Murray Bridge (Pallamanna) has had ca 19mm, hopefully similar in Mannum region.

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#1480283 - 14/12/2018 11:43 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
betsuin Offline
Weather Freak

Registered: 07/04/2010
Posts: 759
Loc: Magill, Adelaide
Very impressive:



9mm in my rain gauge now.

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#1480400 - 14/12/2018 15:25 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Markus Offline
Weatherzone Moderator

Registered: 02/12/2010
Posts: 2239
Loc: Clare, SA
Warm front overnight eventually occluding with a cold front overtaking this morning over centralish areas. Very rare

Orographics were absolutely pumping here last night, some places to 9am within 20km of here had 3.5mm to 9am, Booborowie just up the road 0.8mm.

Not as heavy as initially expected for the eastern Adelaide Hills but still some nice falls. More to come in the next couple of days. Will tick over nicely.

Here it rained/drizzled most of the night and morning. 41.5mm in the gauge, 43.5mm at Spring Gully (this is the event total including today's after 9am rain and the before 9am rain yesty) I've heard an unconfirmed report of 50mm near Sevenhill.

Some CAPE and very moist air overhead atm, hoping we might see some heavy showers later today, then more rain tomorrow. December's nearly becoming more reliable than winter months here lol
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#1480409 - 14/12/2018 15:41 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: roves]
Markus Offline
Weatherzone Moderator

Registered: 02/12/2010
Posts: 2239
Loc: Clare, SA
Originally Posted By: roves
OMG woke up to find 30mm in gauge this morning on top of 12mm yesterday, its a bit wet here.


Well overdue for you! Great to hear
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#1480479 - 14/12/2018 17:58 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
willitrainagain Offline
Weather Freak

Registered: 13/12/2011
Posts: 591
Loc: Mt Barker S.A.
25mm so far and starting to rain again

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#1480492 - 14/12/2018 18:24 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Markus Offline
Weatherzone Moderator

Registered: 02/12/2010
Posts: 2239
Loc: Clare, SA
surely flash flooding potential through the mid north at the moment with this convergent arm off the low. very slow moving lines of heavy showers
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#1480508 - 14/12/2018 18:55 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14984
Loc: Seaford Meadows, SA
I'd say you are getting trained by that line of showers Helen, looked fairly substantial and heavy.

TS cool


Edited by Thunderstruck (14/12/2018 18:55)

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#1480517 - 14/12/2018 19:16 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
Helen Offline
Moderator

Registered: 07/11/2001
Posts: 9669
Loc: Mid North, SA
Originally Posted By: Thunderstruck
I'd say you are getting trained by that line of showers Helen, looked fairly substantial and heavy.

TS cool

Left for Port Pirie at 4pm and it was as dry as chips here... just got back home and the front yard is underwater, the culvert out the front has decent running water and I'm soaked through from pulling the deck blinds down... and it's still coming down. grin

You sure called this one well, Lennie!!! Cheers, sweetie. smile
_________________________
2017 YTD - 67.8mm Yearly Average - 403mm
Jan - 32.8mm (10mm) / Feb - 35.0mm (10mm) / Mar - - (15mm) / Apr - - (31mm)
May - - (46mm) / June - - (51mm) / July - - (59mm) / Aug - - (54mm)
Sept - - (48mm) / Oct - - (38mm) / Nov - - (23mm) / Dec - - (18mm)
Total 2016 - 637.2mm



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#1480535 - 14/12/2018 19:53 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
betsuin Offline
Weather Freak

Registered: 07/04/2010
Posts: 759
Loc: Magill, Adelaide
Oh - big dust storms:


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#1480950 - 15/12/2018 19:20 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
betsuin Offline
Weather Freak

Registered: 07/04/2010
Posts: 759
Loc: Magill, Adelaide
And more dust storms evident on satellite image:


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#1481176 - 16/12/2018 11:57 Re: SA Cut off low, windy showers/rain poss small hail Dec 13th-15th [Re: Thunderstruck]
betsuin Offline
Weather Freak

Registered: 07/04/2010
Posts: 759
Loc: Magill, Adelaide
Another 6mm of rain over night.

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