Victoria: Low pressure System and Rain event. August 9th-15th 2009

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Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Karl Lijnders on Fri Aug 07, 2009 5:37 am

Well a crucial rain event is likely to develop over SE Australia in the coming week in the form of low pressure system.

What makes this system so critical is that much of the south has had frequent rainfall the past month and things are getting wet so the catchments could score big time!! This could me worth watching.

It needs another day or two but it has the potential to produce some very good falls. Possibly monthly values in some spots.
BTW with the easterly developing on the east coast, there appears to be a block developing also so this will keep the system slow.
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Johnno on Fri Aug 07, 2009 10:05 am

Heres what the Queensland BOM think of it updated half hour ago...

QUEENSLAND WEATHER FORECAST
Issued at 11:35am EST on Friday the 7th of August 2009


IDQ1070002
EXTENDED OUTLOOK

On Sunday the next continental high will move over northern New South Wales. The
surge in S/SE winds, expected to move rapidly up the southern Queensland coast
on Saturday, will reach the Northern Tropical Coast and enhance showers. As the
high drifts eastwards winds over southern Queensland winds over these waters
will ease considerably. Dry SE winds over the interior will maintain fine
conditions.

On Monday morning the combination of dry light winds and clear skies over
southern districts will again produce widespread frost and a few places will
record negative overnight minimum temperatures. The weak high that moved over
New South Wales on Sunday continues to move into the Pacific.

Another burst of
cold air over Victoria
will push another slower moving S'ly change into the
Channel Country. Ahead of this change winds over the interior will turn NW/NW
again and produce warm days with temperatures about 3 to 5 degrees above
average. The cold air mass over Victoria becomes stationary and a low forms over
central Victoria.
This slowing of the weather systems is why the S'ly change in
confined to the Channel Country and eventually weakens out.

On Tuesday the global computer models indicate the formation of a blocking
pattern over SE Australia. That means the low over Victoria becomes stationary
and the high over New Zealand also become stationary.
So the warm NW/NE winds
that became established over the interior on Monday persist during Tuesday and
Wednesday. A short wave upper system may bring some cloud into southern
districts however little or no rain is expected.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Johnno on Fri Aug 07, 2009 10:10 am

And the Tasmanian BOM updated roughly half hr ago...

Australian Government Bureau of Meteorology
Tasmania

Overview of the Weather
Issued at 11:30am on Friday the 7th of August 2009

A high over Victoria with a low to the south of Tasmania on Saturday, direct a northwest flow over the state. The systems move slowly east on Sunday as another high strengthens over the Southern Ocean and Bight and a low develops over South Australia with the flow tending easterly. On Monday and Tuesday, the low over southeast Australia deepens as the high moves to the south maintaining an easterly flow over Tasmania.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Mantis on Fri Aug 07, 2009 11:18 am

Yes, this one looks promising eh.
Send her down huey

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Johnno on Fri Aug 07, 2009 1:34 pm

Not a done deal with this one yet.. GFS has the jitters now that we are nearing the end of it keeping the main rain SW of us and UK has backed off abit as well keeping the low in the Upslide northerly well west of us Monday morning and main rain south of us.. Don't know what to believe still looks to be shuffling around fair bit even though were on the eve preety much of this event.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Karl Lijnders on Fri Aug 07, 2009 3:09 pm

I don't think it's looking good and I think now the block will occur too far west for us to get significant rainfall - sigh. We live in VIC. I forgot Wink
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  DC449 on Fri Aug 07, 2009 4:02 pm

Your kidding me.... Rolling Eyes
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  norfolk on Fri Aug 07, 2009 5:52 pm

seen it happen before, good rain to the north and south but central areas miss out. Someone explain to me why this is any different?

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Power Storm on Fri Aug 07, 2009 7:36 pm

It was looking good Tony, but as usual the models chop and change, so a bit of a downgrade now, still time for things to improve, so not all hope lost, but at this stage, the south and east look like they will benefit again.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  droughtbreaker on Fri Aug 07, 2009 7:50 pm

It was only one run of GFS that downgraded. The latest run of GFS for the coming week now has 25-50mm back again for ranges and western VIC and 10-25mm elsewhere. EC still looks better IMO.

What we are seeing in the progs is a complex situation with cut off lows coming in over the top of highs and quite messy so expect models to chop around a lot right up to the event. Rainfall progs will go up and down and up and down again.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  hillybilly on Fri Aug 07, 2009 8:07 pm

Well I reckon it still looks very promising. I wouldn't read too much into the rainfall details - these are critical dependent on the fine detail of where the warm air advection sits and where the low tracks which won't be clear until just before it starts to rain - but with the low likely to develop over western Victoria with a sharp upper trough we will see some very healthy totals. The low then slowly gets dragged into the westerlies allowing a sequence of fronts to move up later next week.

EC has widespread rain right through from Sunday onwards - perhaps not all falling in Melbourne - but again don't read too much into the fine detail. UK has a similar scenario (this model almost always under does shower rain so the total are usually too low), and GFS has widespread 20-50mm.

Will now wait on the 12Z and then 0Z Saturday to get a better idea.

At this stage would be very disappointed not to see 20mm in Ferny Creek by next friday, and would not be surprised to see 40mm. This will not break our drought (that'll take years of good rainfall) but any rain is good rain.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Karl Lijnders on Fri Aug 07, 2009 9:57 pm

Yeah I'm still not convinced until I see it developing on satellite. At this point it needs to fall across central VIC and our catchments to really help our defecits here.

It will rain in the west and north regardless.
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  hillybilly on Sat Aug 08, 2009 5:30 am

The 12Z updates are in and look very promising GFS, EC and UK follow a very similar script with a low deepening rapidly over eastern SA/western Vic on Sun/Monday. There is a very healthy infeed of tropical moisture coming in off the Indian Ocean near 30S which provides the source of moisture while the low develops on frontal boundary you can see moving up from south of Perth ATM.

The low then tracks slowly southeast across the state eventually be absorbed back into the westerlies.

Both EC and GFS have widespread 20mm+ falls - best of it will be to the northeast and southeast of the parent low. Also wouldn't be suprised to see some storms mid week with moist low levels and a deep upper low parked right over Vic. Westerlies then establish late in the week with a sequence of strong fronts.

BTW it looks too warm for snow except really high with 850Ts of 2-5C across the alps (Jake - take your rain coat!).

We are only 48 hours out to the event starting, so with all major models on board it looks good.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Karl Lijnders on Sat Aug 08, 2009 6:06 am

in a scenario such as this one, which is indicative of spring, we cab get upwards of 30-50mm across wide areas. All if a sudden EC places Melbourne in the sweet spot with upslide NE/SE flow and rain wrapping over us

Still a waiting game but things look much better.
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  droughtbreaker on Sat Aug 08, 2009 10:02 am

Certainly looks good, in fact easily the best outlook of the year to date given it is right on our doorstep so has a very low chance of failing IMO. Hopefully this is an indication of what to expect this coming spring. We are coming into the wettest time of the year for central VIC (although in recent years practically the driest No ) and it is very encouraging to see so much moisture available and still coming down from the NW Indian Ocean despite the general El Nino pattern. If we can somehow get through September and October with decent rainfall then the summer mightn't necessarily be that bad. I know I'm looking way too far ahead with that assessment but at least the short term looks really promising.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Karl Lijnders on Sat Aug 08, 2009 4:36 pm

Andrew I think that is a fair assessment. Looking reasonable if we could score some better low pressure systems into early spring and some strong cold fronts like the past weeks.

I think the frequency of rainfall is key to seeing the deficiancies ease somewhat in Central VIC.

OK so this system looks to be shaping up nicely. Plenty of moisture and a slowing down in the isobaric flow will mean that this low will produce moderate falls across much of the state with heavy falls about the dividing range and south as we get into a more crosshore/onshore flow.

Tomorrow looks like the buildup day with cloud thickening and rain developing from the west and southwest later. Could be up to 5mm in this initial band across the south maybe 10mm in the SW and Wimmera by Monday 9am.

Monday the rain will increase across the south and west and develop over the northern and far east later but lighter falls. Moderate falls developing about the dividing range and local thunderstorms over the NW later extending eastwards later.

Tuesday rain and thunderstorms over southern and eastern VIC tending to scattered showers over the northern plains. Moderate to heavy falls in south central and eastern W district.

Wednesday will see rain and drizzle over the south and east, tending to showers from the west. Isolated thunderstorms inland during the afternoon. Moderate to heavy falls contracting further east and south later.

I think there will be more detail as we get into this weekend. I hope we can score this rain event after copious rainfall in the past month in the south. Time to play catch up in the northern half of the state and this is the best chance the state has seen since before Christmas last year.
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  floydlove on Sat Aug 08, 2009 5:11 pm

Hi guys,

Been a long time now, not sure if anyone remembers me. Was in hospital all this time but have managed to stumble across this forum as the last I remember it a lot of people were banned from the other one. Again, not the best year for weather but back in April I did experience some of the loudest thunder and closest CG lightning for some time. I'm sure it was talked about a lot in here or on the other forum. Wink

Looking like a good event to get back into it, will be hoping for at least 20mm for the week now.

Seems this forum is going along nicely with, from a quick glance, a good bunch of knowledgeable and not-so-knowledgeable people along with the regulars and gurus. Smile

Anywho hoping for some decent falls for most.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  SC on Sat Aug 08, 2009 5:40 pm

Welcome Floyd,
Sorry to hear of your hospital stint. Hope your better now. There is plenty of weather obs going on on this site. You'll love it.
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  hillybilly on Sat Aug 08, 2009 5:42 pm

Welcome Floyd (and spread the word) - hope you are better now.

Not much to add. This system is shaping up nicely - though it is hard to pin down the details which are critically important for rainfall totals. Will be interesting to see how far east the rain gets tomorrow.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Karl Lijnders on Sat Aug 08, 2009 5:46 pm

I think it should make it by about 9pm tomorrow night with the trajectory moving east rather than south.

Floyd I am glad that you are back and looking forward to chatting weather with you again, and I trust the rest of the year is with you out of hospital!!!!
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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Johnno on Sun Aug 09, 2009 5:17 am

Good to see you back Floyd hope your better now mate was wondering where you had been


Not sure what to make about this system is it my imagination or has EC weakened it this morning? Or still looks the same to others? I expect 20mm here between tomorrow until Wednesday night would be dissapointed with any less given the set up/airstream is NE then SE for a while but would easily have to be the best prospect for this side of town for a while probably since the December event of last year. Pity this event couldn't happen between October to April the rainfall could be doubled cos of storms & pity the bay is at its coldest at the moment for the year but beggers can't be choosers.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  hillybilly on Sun Aug 09, 2009 7:04 am

Agree Johnno. EC has definitely downgraded - for southern Vic. The system has a slightly more northerly track which reduces the rainfall totals. GFS and UK look pretty similar.

Would expect the best rain today to be limited to the far southeast of Vic slowly spreading east.

With a small slow moving system (with tightly focussed upslide) I anticipate this could be quite a frustrating system with heavy showers training over areas and big variations in rainfall totals over small distances. Will be a case of watching the radar.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  I_Love_Storms on Sun Aug 09, 2009 11:16 am

I'm more confident for some higher rainfall totals. The low pressure system looks to have formed a considerable cloud mass that will move into Victoria today and linger for an extended period. I expect widespread rainfall across Western and Central Victoria over the 36-48 hours from 6pm Sunday evening, moderating somewhat after this period. I am still unsure whether Eastern Victoria will receive the same levels of rainfall as the cloud mass is still a fair distance away.

The current National Loop shows widespread rainfall over southern areas of SA and this should push across into Western Victoria tonight. As long as the westerlies persist, rainfall over central to southern Vic will be limited, and higher totals will be realised as the airflow tends Easterly later Monday and into Tuesday.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  Twister on Sun Aug 09, 2009 2:34 pm

Yeah not getting two pumped about this low, while it looks nice and will bring lots of showers there is no major moisture source, so large falls i struggle to see. Will all be very light so will need it to rain many hours to get decent amounts still its looking ok and Much better than a big high over us expecting.
12-15mm here for the week hills and Sw should do better.
The forecast for Melb been patchy rain is a more accurate forecast, down grade yes, but is right in my eyes.
Wont be periods of rain just patchs of rain about.

Just dont expect 20-30mm falls maybe in hills and Sw but thats it,

If we had a Moist Ne or Nw flow then i would be quite exticed, while we are getting some moisture from the jet steam and the sourthen ocean its not great but it will do.

Watch for a cloudly and a little rain, few days ahead

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

Post  I_Love_Storms on Sun Aug 09, 2009 2:40 pm

Quite disappointed at the latest forecast. Downgrade to 'a little rain' for the next couple of days. It is a shame that there is not much moisture in the air, I guess that is what you get when we are in this weather pattern.

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Re: Victoria: Low pressure System and Rain event. August 9th-15th 2009

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