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VIC - Major low and possible cold outbreak: May 7-14 2018

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VIC - Major low and possible cold outbreak: May 7-14 2018

Post by hillybilly » Sun May 06, 2018 7:51 am

Major low showing up across every model for the week ahead as a strengthing high to our west throws up a strong front which cuts off near Bass Strait. This then becomes slow moving eventually moving into the Tasman Sea, possibly further north near central NSW. Uppers are cold, with 850Ts dipping well into the negatives, so heavy snow in the alps and possibly into the subalpine (though backend may bring rain into the alpine areas). Looks like a couple of miserable days, to break up the monotony of the endless summer :D

Rain totals are mixed, but generally 20-60mm in the south and 10-40mm north. Heavy falls likely, but depends on the final placement of the low.

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Re: Major low and possible cold outbreak : May 7-14

Post by stevco123 » Sun May 06, 2018 9:33 am

Weather station now going for a max of 11 on Thursday and 13 on Friday. 18 hours ago it was saying 20 for both days :o :o :o
https://www.weatherlink.com/bulletin/53 ... 76dd68e8bc: for current weather updated every 2 minutes

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Re: Major low and possible cold outbreak : May 7-14

Post by JasmineStorm » Sun May 06, 2018 11:21 am

As with most sudden stratospheric warming events, it gets extreme and this one is a ripper. Polar jet completely displaced now by Friday. Rainfall is going to be impossible to predict until the surface low circulates IMO but the wind will be something else with around a 40 hPa pressure gradient within 900 km. I'm tipping that the BoM will be holding a press conference on Wednesday.
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Re: Major low and possible cold outbreak : May 7-14

Post by JasmineStorm » Sun May 06, 2018 3:37 pm

UKMet latest has a 984 hPa cyclonic cold core Bass strait gyre with a huge southern fetch and south westerly attack into central Vic on Friday. It then heads west towards central areas. Trampolines will be sailing across suburbs if that is right.

FYI - @120 hours the UK model is currently 87% accurate which is 2nd to EC near 90%. GFS 3rd at 84%, CMC 4th at 83% 4th, U.S Navy 5th at 79%. Personally I believe Access R (72 hour range) and Access C (36 hour range) are more accurate when it gets closer.
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Re: Major low and possible cold outbreak : May 7-14

Post by Gordon » Sun May 06, 2018 4:17 pm

Surprised to see 00Z GFS bring everything west; bucking a general trend for the system to be edging east as it was picked up by the models.

It is interesting that our latest BOM forecast is for a 'Shower or Two' Thursday and Friday. I would have thought a shower or twenty, but what would I know? :?

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Re: Major low and possible cold outbreak : May 7-14

Post by Wilko » Sun May 06, 2018 4:19 pm

Wow I love those systems that retrograde to the west
Bring it on 😮

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Re: Major low and possible cold outbreak : May 7-14

Post by Gordon » Sun May 06, 2018 6:46 pm

EC & GFS both have us down for about 60mm now.

Meanwhile the silence from BOM is deafening for what seems very likely to be a major weather event. Not even a murmur on Twitter, or in the forecast 'language'. I hear those who say it's too far out to lock in, and the models are still moving the 'bullseye' around, but underestimating forecast rainfall, wind, temps etc. is just as inaccurate as overestimating.

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Re: Major low and possible cold outbreak : May 7-14

Post by JasmineStorm » Sun May 06, 2018 8:05 pm

Yes Gordon, interesting topic with the BoM. The 4.20pm forecast is already old news as most of the analysis is done off the 12z runs. I think they need a severe weather outlook tab on the website to show upcoming possibilities over the next 5 days and is updated after the afternoon 00z runs.

Trying to look over the course history for compariable systems in May. Year 2000 looks similar but these sea surface temperatures I think might be a couple of degrees warmer. It could be an unprecedented set up IMO.

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Re: Major low and possible cold outbreak : May 7-14

Post by Skywalker » Sun May 06, 2018 8:13 pm

I don't have any issues with the BOM being rather conservative at this stage. I've lost count of the amount of downgrades & fizzers we have experienced during the past year. Quite happy to sit back & wait until we are 24 hours out before making any crazy predictions on what may or may not happen.
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Re: Major low and possible cold outbreak : May 7-14

Post by Onetahuti » Sun May 06, 2018 8:24 pm

Skywalker wrote:
Sun May 06, 2018 8:13 pm
I don't have any issues with the BOM being rather conservative at this stage. I've lost count of the amount of downgrades & fizzers we have experienced during the past year. Quite happy to sit back & wait until we are 24 hours out before making any crazy predictions on what may or may not happen.

The BOM is letting the media amble along in it's usual blissful ignorance instead of proclaiming the end of civilization as we know it, though I tend to going by past experience wager more on downgrades than what the worst of any of the models are suggesting at this point in time.

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Re: Major low and possible cold outbreak : May 7-14

Post by Sean » Sun May 06, 2018 8:49 pm

Onetahuti wrote:
Sun May 06, 2018 8:24 pm
Skywalker wrote:
Sun May 06, 2018 8:13 pm
I don't have any issues with the BOM being rather conservative at this stage. I've lost count of the amount of downgrades & fizzers we have experienced during the past year. Quite happy to sit back & wait until we are 24 hours out before making any crazy predictions on what may or may not happen.

The BOM is letting the media amble along in it's usual blissful ignorance instead of proclaiming the end of civilization as we know it, though I tend to going by past experience wager more on downgrades than what the worst of any of the models are suggesting at this point in time.
We see it time and time again... This upcoming event will probably bring some blustery wind and showers, nothing more unless you're in the alps. I hate to be a cynic but Melbourne's boring weather and history of fizzers made me this way.

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Re: Major low and possible cold outbreak : May 7-14

Post by StratoBendigo » Sun May 06, 2018 9:54 pm

These complex Low systems can be hit or miss as far as where the rain falls. Wrap-arounds can be notorious for dumping massive amounts of rain in a narrow band with little falling either side.

We got very lucky in April last year when a wrap-around from the SW absolutely drenched us with 36mm in a few hours. Unusually heavy rain North of the Divide for such a system.

Who knows where the wrap-around from this storm might strike?

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Re: Major low and possible cold outbreak : May 7-14

Post by JasmineStorm » Mon May 07, 2018 6:34 am

Latest runs have EC and CMC now initially having multiple cores and then consolidating around Bass strait with a full blown 'fujiwhara effect' :) UKMet going the more traditional bombing single low down to 981 hPa and possible sting jet.

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Re: Major low and possible cold outbreak : May 7-14

Post by Gordon » Mon May 07, 2018 9:05 am

As we're now only a couple of days out from the beginning of the system proper, it's worth uploading Water & Land's take on it (an average of several models). Three big centres (50mm cumulative rainfall plus): East Gippsland, central Vic, and south-east Tas:
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Re: Major low and possible cold outbreak : May 7-14

Post by Tassiedave » Mon May 07, 2018 9:22 am

Getting excited about this event in Tassie, like Gippsland and many other areas of Victoria the East Coast of Tassie desperately needs rain. I'm worried that the margins are fine and hoping the LOW/s don't form too far east.

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Re: Major low and possible cold outbreak : May 7-14

Post by Gordon » Mon May 07, 2018 9:33 am

Yes that's always the concern with ECL-type systems, although encouragingly, this system has shown a tendency to drift west since it was first picked up by the models. (I wish I'd kept a pic of WATL from about 3 days ago - it showed a classic ECL dumping a ton of rain in far East Gippsland and little rain elsewhere.)

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Re: Major low and possible cold outbreak : May 7-14

Post by JasmineStorm » Mon May 07, 2018 9:48 am

No matter which model you look at, its extreme. I thought I'd give the latest GFS a good look....goodness me

GFS 18Z is now favouring the UKMet scenario. The polar jet is displaced and interacts with the sub tropical jet into the cut off. This looks like a nasty sting jet to me. The wrap around south westerly cyclonic attack into central Victoria would be a major wind hit. Moisture advection significant as well for rain. Boats around the bays will want to have good moorings. The Melbourne wind record of a 121 km/h gust would probably be passed on that GFS run.
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Re: Major low and possible cold outbreak : May 7-14

Post by JasmineStorm » Mon May 07, 2018 11:41 am

I've looked into the famous May events since 1999 on the BoM MSLP's archive and not one is comparable to the models projections at the moment. Past May events have had the surface low more south. There are some slight comparable set up's in June and July events but they didn't have the balmy sea surface temperatures that currently exist. On Friday morning, there is a 50c temp difference between Bass strait surface temperature and 500 hPa. As mentioned by others, the surface low position will be crucial on where the wind and rain extremes occur. That is the great unknown until it happens really.

I'm looking forward to the BoM's 4 day map today :)

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Re: Major low and possible cold outbreak : May 7-14

Post by Wilko » Mon May 07, 2018 12:07 pm

Awesome
Love your input Jasmine
Please keep the updates coming

Ps anything can unfold at the 24th hour “that’s weather”
The real value the lead up to these events that gets us all excited

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Re: Major low and possible cold outbreak : May 7-14

Post by Gordon » Mon May 07, 2018 12:30 pm

I genuinely would love to be a fly on the wall at BOM right now. It would be fascinating to hear the conversations leading up to the point when they decide to acknowledge the potential for severe weather (or possibly not if an unlikely downgrade occurs.)

It's undoubtedly a tough call - advance warning for people like me who have very weather-dependant businesses - or individuals/ agencies who are likely to be affected by severe weather; vs the risk of being accused of 'crying wolf' if it doesn't happen. Personally I'd favour the former approach, properly framed with a risk rating, as per the NZ MetService - like this http://www.metservice.com/warnings/seve ... er-outlook.
Last edited by Gordon on Mon May 07, 2018 1:28 pm, edited 1 time in total.

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