Looking towards substantial rainfall for SE Australia

[stratospear]

Forecast models are now toying with a burst of rain in 8 days time (Dec 10 onwards) with an associated cold front. Maybe not the big one though...

[johnno]

We should get low level moisture slowly building from the NE all of next week and at the same time we should see mid level moisture build from the Indian ocean as a Cyclone or tropical low SW of Java both of these sources of moisture should interact with a trough or front between Friday and Sunday next week.. I think models are having trouble in how the rainfall will be distributed but knowing we have good moisture from both these points I would expect good rainfall and good thunderstorm activity

[Anthony Violi]

Its on again, models have shifted this morning into a good ssytem now developing through WA and instead of heading SW, will move SE over our latitudes and drag in enormous amounts of moisture due to the NE flow as Johnno says, and the burst of MJO as well. At this stage its unclear as to rainfall because it will depend on the cradle set up of the high, no model has it yet and it may not occur, saving us from another large scale flood event. So a few more days and then it becomes clearer, but good rain and thunderstorm activity will develop late week.

[Lily]

Uh-oh, there goes cricket again...

[droughtbreaker]

I can see some decent storms this time around as the air mass dries out a little after a bit of a cold burst tomorrow and then moisture builds up over the week in the NE's but remains at moderate levels for most of that time. Once we get the mid level moisture in from the NW and a slow moving trough approaches, we could start of with a storm outbreak out of clear air before more general rain arrives. The embedded stuff that we have been seeing recently (and also last summer) is a result of very high moisture levels prevailing well before a trough or front actually approaches.

[Anthony Violi]

Dec 1 i posted to be aware...well the time is now. Within a fortnight, due to the passage of the MJO, most of Australia will be suffering from serious flooding. Going to be a re run of last year it seems. This one looks to be it in a weeks time, i like this set up because the low that is about to form in the Tasman will be the catalyst in the form of the block. As long as the block stays intact, massive rainfall can be expected across all of Eastern Australia.

[Meso]

Yeah, next weekend through to the middle of the following week look very wet.

[Ken]

The EC ensemble has been painting some modest probabilities of a wet signal around SE Australia mid to late this month.

Meanwhile both the North American Ensemble Forecast System and the EC ensemble are suggesting moderate to strong probabilities of a cool signal to spread again across a fair bit of Australia (including eastern parts of SE Oz) between around mid Dec and early Jan, but particularly pronounced over NSW. One of the reasons for this is evident on EC's forecast MSLP anomaly probability maps - it's currently suggesting moderate probabilities of lower than normal pressures around the Tasman Sea mid/late this month and therefore dragging up cool air up over SE Oz.

[HarleyB]

Anthony, do you think the approaching system in 7 days' time is "the big one" or do you think there is a bigger one further out that the models cannot see yet?

[Anthony Violi]

I think it largely depends on the block maintaining the cradled cut off that all models are going for tonight. If tonights set up was to occur we could be seeing 150mm through half of Australia as minimum, and at least that through Victoria. Upslide from the NE for two days would deliver so much rain with that moisture profile it would put us under water.

Given SST are above average surrounding us for the next few months, DPs of 20+ are likely down here again, meaning every systems rainfall will be top end. ACCESS has Dps of 22-24, maybe a tad high but reflective of how much moisture there will be available once it cuts off. This is the first system this Spring/Summer that has this much moisture available thanks to the MJO passing through, so it will be a good guide as to what the next few months has in store for us. I think we can wait a couple of days and see if the block takes place, but with all models going for it looks the goods at this stage.

[eegs]

Wow. The national loop already shows much of the east getting a flogging. Anywhere from Emerald in central Qld to Melbourne looks fully primed for next weekend.

[Lily]

http://www.heraldsun.com.au/news/more-n ... 6219417342" onclick="window.open(this.href);return false;

Sun lovers hold off, there's more rain to come

by: Staff Writer From: Herald Sun December 11, 2011 9:28PM




SUMMER is off to a soggy start with predictions of consecutive weekend washouts.

Wet and muggy conditions are forecast to return by the end of this week, bringing more rain to our soaked state.

But the jury is still out on whether we will have a repeat of last year's widespread summer rain.

Another weaker La Nina system is expected to have an impact but hotter-than-average daily temperatures could make all the difference.

Melbourne copped the biggest drenching at the weekend with between 25 and 40mm recorded across the metropolitan area.

Bureau of Meteorology forecaster Peter Newham said conditions would improve through the week before northerly winds would bring moist conditions late on Friday.

"It should be fine between now and Thursday but then we will see a return of the instability and the possibility of storms redeveloping over the weekend," he said.

The broader outlook for the next three months included a 40-50 per cent chance of above-average rainfall, he said.

Long-range weather forecaster Dennis Luke said wet and humid conditions would continue through January.

He said Christmas Day was likely to be wet and humid while New Year's Eve should be dry and warm.

[Rivergirl]

Just came across this article from The Age as well

Brace for a topsy-turvy summer

It's a summer weather forecast to make holidaymakers break into a cold sweat.

Victorians can expect increased thunderstorm activity and higher-than-average rainfalls this summer.

Read more: http://www.theage.com.au/environment/we ... z1ggmnDMgL" onclick="window.open(this.href);return false;

Parts of Australia's east coast, particularly New South Wales and Queensland, are expected to be drenched in higher-than-average rainfall this summer due to the strengthening of La Nina weather conditions.

Cooler temperatures are expected to accompany the downpours, with the mercury forecast to dip slightly below the summer average in those states. Northern Australia is also at increased risk of tropical cyclones during La Nina.

Story continues below Weatherzone senior meteorologist Josh Fisher said this year's La Nina event was not predicted to be as severe as the conditions in the 2010-11 summer, which saw Queensland and Victoria lashed by devastating rain and floods, but it would still have a noticeable impact through the next three months.

In Victoria, long-term-average temperatures and rainfall are expected to remain about average across the three months of summer.

But Victoria's topsy-turvy start to the season - with hot days interspersed with thunderstorms and chillier conditions - is set to continue throughout the next three months. It will be accompanied by higher humidity levels, Mr Fisher said.

"Rainfalls are expected to stay close to average or slightly above in Victoria, which will also keep temperatures close to average, but this doesn't rule out those extreme heat events where we see those temperatures climb up to around 40 degrees. Like we've already seen during these first two weeks of summer, there's going to be a large variation," Mr Fisher said.

Mr Fisher said increased thunderstorm activity was also expected to strike right across Australia's east coast due to La Nina.

"This is a feature that we're likely to see right throughout the summer, including anywhere from South Australia to Victoria, News South Wales and Queensland," Mr Fisher said.

During the first four days of December daytime temperatures in Melbourne remained below 21 degrees, the coolest start to summer in 24 years.

The temperature rebounded during the second week of summer, with the mercury climbing as high as 32 degrees on December 8, followed by rain and thunderstorms. The city received 34 millimetres of rain in just 12 hours from 5pm on December 10, more than half of the December rainfall average.

Mr Fisher said during a La Nina event, sea surface temperatures near South America cooled below average while sea surface temperatures close to Australia warmed up.

That affected atmospheric circulation, leading to a strengthening of easterly trade winds over the tropical Pacific.

The winds gained large amounts of water over the Coral Sea, which were then pushed over eastern parts of Australia.

Meantime after a wet start to December, Western Australia is forecast to receive average rainfall and temperatures for the remainder of the summer.

Severe storms have dumped 76 millimetres on Perth already this month, well above the long-term average of just six millimetres - making it the wettest December in 50 years, Mr Fisher said.

He said that above average-rainfall was not linked to La Nina, but a warming of sea temperatures off Western Australia. Rainfall was expected to be around the long-term average of 10 millimetres a month or slightly more for the rest of summer, Mr Fisher said.

"Western Australia has seen a lot of rain so far this month but that's really been heavy rain over a day or two. Summer is usually their drier months," he said.



Read more: http://www.theage.com.au/environment/we ... z1ggm1CVYr" onclick="window.open(this.href);return false;

[Anthony Violi]

Going to be a very wet period coming up..the signal Ken was alluding too, GFS is all over it and has the potential to tap into the heat next week. Also progging a cyclone over Darwin Xmas Eve....1974 all over again and could get dragged south or East.

I think that flooding across much of Australia will become a big problem this summer. We havent even got anywhere near the Dps we will see in 4 weeks time onwards. Last summer was all tropical systems moving south, this year we have cooler mids down south thanks to mid level troughs lingering through the south of the country, if they connect at the right time will be even worse.

[stratospear]

If 14 day GFS outlook comes to pass.... we could be in big trouble!
http://www.wxmaps.org/pix/prec7.html" onclick="window.open(this.href);return false;

[Geoff]

Seems to be some agreement between quite a few of the major models this evening for something substantial coming along around Sunday 8th January. It seems they have a large tropical depression over WA moving south and then coming east as it gets caught up in the general westerly flow as a cold front sweeps in behind it. It would continue the run we've had of late of stormy Sundays through the last couple of months. Something to chew on as we wait for the upcoming rather boring spell to move on.

[Anthony Violi]

Check this out.



We are getting into a very interesting period now. SSTs around OZ are warmer than normal, especially the Indian Ocean side. We could be setting up for some amazing rainfall in the next few months. All summer the Indian hasnt been favourable at all, if the IOD goes negative we could see huge falls through the interior, and the southern states.

Notice most of the oceans are cooler as one would expect during the NH winter. But one thing to notice is the hot spots in the SH are caused by the highs not moving. Very interesting that the blocking pattern has lasted a couple of weeks as the have only just started to get really warm in the last week or so.

I think we are primed for a big few months, even though the 12 month outlook gives central a decile 1 for February.

[Ken]

Although this may or may not reach as far south as Vic, both the EC ensemble and NAEFS are suggesting a wet signal for parts of NSW or southern QLD around the 2nd week of Jan. Also noteworthy is the cool signal that the EC ensemble spreads across much of the southern half of Oz during this time.

[droughtbreaker]

There does appear to be a very broad area of milder moisture laden air set to flood in over the continent after we get through a couple of cycles of highs/troughs passing through. I guess this is where the cool signal is coming from. It could potentially be a wet period as well. It would be nice if it came off as there is quite a bank of summer heat build up affecting the continent atm which needs a good flush out or it could potentially turn nasty later into the month.

[johnno]

Yep the 1st of the broad upper highs over the mainland which is the main reason why most of us are getting this heat or will be.. Haven't really had any upper highs up til this point but does happen fairly regularly this pattern in January, I guess it had to happen sooner or later.. Hopefully it will be flushed out in 7-10 days time