LWT = Long wave trough

It's a little hard to explain and I'm certainly no expert, but basically you will notice that within the westerly wind belt (to the south of Aus in the Southern Ocean) there is a general wave pattern that tends to circulate around the hemisphere, the westerlies are never uniform or straight lines the whole way around the globe.

Where these waves are broad and have high amplitude it is known as a LWT and usually carries cooler upper air towards Southern Aus from deep in the Southern Ocean. Where you have a LWT over your part of the globe it tends to amplify cold front/trough systems or low pressure systems. Currently we have been under the influence of an upper high pressure ridge to the west which has effectively 'taken over' systems coming through from the west causing them to weaken right out whilst the LWT has been stalling between WA and SA. The general expectation is that this LWT will now peak over our part of the country seeing a return to decent fronts/troughs and low pressure systems.

I have explained this terribly I know but I don't really understand it all that well either it seems very complex to me. I'll have to read up on it more.

Andrew has done OK with his explanation.
A lot of people are left floundering with that one!
WZ's explanation of a long wave trough can be found in the "glossary" link on the WZ home page along with a lot of other brief but descriptive outlines of weather and climate phenomena.
Here it is;
Longwave trough
A trough in the prevailing westerly flow aloft which is characterized by large length and (usually) long duration. Generally, there are no more than about five longwave troughs around the Southern Hemisphere at any given time. Their position and intensity govern general weather patterns (e.g., hot/cold, wet/dry) over periods of days, weeks, or months.

Smaller disturbances (e.g., shortwave troughs) typically move more rapidly through the broader flow of a longwave trough, producing weather changes over shorter time periods (a day or less).

For an actual analysis of the current southern hemisphere long wave patterns as they move around Antarctica, go to the BOM's numerical prediction division and have a look at the products such as this one which gives the current long wave pattern.
Information such as this will give you a much better idea on the immense amount of data that the meteorologists have to deal with when they are drawing up forecasts, particularly for international aviation and maritime use.
Not only international aircraft use this data for flight safety reasons but also to pick winds that will favour fuel and time savings.
Ships use this info to avoid bad weather and to cut sailing times between ports by choosing sea and wind favourable routes.

Thanks folks, very interesting stuff..

I cant see anything substantial for Victoria in the next two weeks. Just mainly dry weather apart from possibly a thundery event (not a rain event) mid to late next week. Worth to watch anyway.

Jake

That low in NQ really ramping up with convection now and could be a source of some useful falls across the inland, particularly the darling catchment over the next few days. not much of a model fan anymore but how good would it be if this pulled off

This is certainly an interesting system. But maybe not so good for the farmers, they'd all become sailors.

looks like some good rain on the way for sydney and brisbane but unfortunately nothing too spectacular for the southern states.... maybe in winter it will be good??

GFS, EC and NOGAPS indicate general inland troughy conditions for parts of next week with a few even going for a renewed infeed coming down from the NW and the coral sea which could bring some good follow up to inland QLD/NSW. i usually dont look beyond 5 days in any basic forecast or model but just glad to see theyre guiding toward a wet spell rather than a dry one. hopefully theyre correct, but hey u gotta try even if theyre not especially when ur in such a dreaded dry spell
:cheers:

Nice one ER - you're onto this already :cheers:

GFS, GASP and NOGAPS looking for some more action coming into inland SE Aus come Friday through Sunday. All showing some decent uppers mixing with some humid air running down from up north. This time they seem to swing the event NE through SE Aus and looking already like there could be some good falls in the Murray / Darling and across into E and NE NSW

Few days away yet but nice to have a heads up on some possible model convergence on another decent rain event

Given the current La Nina and an apparent reversion to the patterns of the 1950s-1970s, plus a forecast upper trough or two, I think we are in for some more heavy rain especially eastern NSW, in the next week to 10 days.

I sure hope so. That last system was a bit disappointing here, although the lingering cooler weather is lovely. Heading back up into the 30s by the weekend though, yuck.

Looks like the NSW BoM are onto it. The wording they use on the State Forecast indicates the lack of concensus on exactly where and when the best rain will be happening...

"There are early signs of a general increase in rainfall potential towards the weekend as moisture levels increase and an upper level trough crosses the state."

Interesting. Might be the Model Guys vs the Models Don't Work Guys.

Our forecast (ACT region/southern tablelands) has weekend days being 31, with what looks like t-storms at the end of both days, your classic hot weather forecast. Hopefully it'll change.

im still sticking to my prediction since late last month of a late jan/early feb rain/storm/flood event for E NSW/SE QLD especially now that we're in a deep la nina and also because that period is active almost every year. by the sounds of the previous few posts that pattern will possibly be repeated

The long time locals are still saying that there is much, much more rain to come. Mr Storm Bird reckons Feb for the big one here on the NSW East coast.

The last decent flood here was in 1994 and both the river mouths have silted up since then. Given that this time of the year we are subjected to King Tides on the coast it leaves the river with little option but to rise and flow over the banks. "Interesting times that we live in!"

Definitely something spooky going on in the Tasman right now...Ever get the feeling that it's screaming at you

And is that a Koala Bears face I see over Northern WA ......

GFS throwing more rain into the picture for Southern Inland Queensland. For us in NSW its looking slightly unstable but nothing major for a short while.

Yeah I think an upper trough and easterly winds will combine to bring rain areas and thunderstorms to E queensland and as winds turn NE next week, that rain focus will penetrate further inland.

I can see it becoming more of a NSW event then into VIC in terms of more convective thunderstorms.

Don't worry about inland QLD, diurnal showers and storms with all that water laying around will continue for the next month on clearer days.

The BOM has removed its 'early signs' prognosis (on the 1630 watch)..probably a good sign that it will be back on again nearer the time.

i was hoping they'd keep it in their forecast and not remove it, doh! but seeing that more than half of QLD has turned into a sea, we should have more moisture to play with. :doh: