Victoria: Christmas Week Rain Event. December 23-25th 2009

[Karl Lijnders]

A fairly exciting period weather wise coming up next week and I have noticed in the thread operating currently that tongues are wagging so it is time to discuss it here. This has the potential to be rather large and useful for the whole state.

Expecting a good period of easterly/northeasterly winds and a trough digging it's heals into the state early next week with showers and storms becoming scattered by Tuesday over the north before spreading throughout by mid week. Due to the enormous amount of tropical moisture over the continent to our NW and N and humid NE winds from the Pacific, a lot of potential is being funnelled over the region.

By late week a long wave trough with the potential for cold air to follow, will see showers and storms increase to rain and plenty of it. There is the risk of seeing this system form a cut off low pressure system in the vicinity and this could see rain become locally heavy favouring the south and east. All pure speculation.

EC wants to drag the low still more east than south, but logic suggests it moving more south than east. NOGAPS supports this and does quite well in these instances from previous events featuring tropical lows and moisture.

How exciting that we could be looking at a fairly wet December.

[Jake Smethurst]

Definatley an exciting time Karl.

Models are a bit shifty with this (and it's a little while out), however I am fairly certain as well that we can dig ourselves a good rain event from all that tropical moisture just waiting to be used. And, I second you opinion Karl, I think there is the chance of a cut-off developing, and if so, it would remind me of the Feb 2005 event (it was then wasn't it??).

Still a while out, but positive signs approaching. General consensus at this stage is pointing towards showers and thunderstorms through the east/northeast on Tuesday spreading throughout Wednesday with a slow-moving trough, and then increasing to rain from the west overnight Wednesday as we get the system approaching or developing on our door step.

[Karl Lijnders]

From the SA BoM...

FORECAST EXPLANATION FOR SA:
A band of rain over agricultural areas with scattered showers and isolated
thunderstorms over pastoral areas all northeast of a line Coober Pedy to Gawler
to Mount Gambier at 11am will continue to ease to showers as a trough moves over
the Northeast Pastoral District today. Isolated light showers are still possible
elsewhere over agricultural areas throughout this afternoon, but is expected to
contract to southern coasts by this evening. Conditions will be hot to very hot
with fresh northerly winds in the northeast where thunderstorms and areas of
raised dust will persist throughout the day, grading to cool to mild about
southern coasts due to a moderate to fresh onshore southwest to southerly flow.

Scattered showers and isolated thunderstorms over the Northeast Pastoral
district will contract to the far northeast Friday morning and clear during the
evening. Isolated showers may persist about southern coasts in the onshore
airstream through to midday Saturday. The rest of the State will be fine with
moderate southwest to southeast winds. It will be cool to mild in the south,
grading to mild to warm in the north.

A high pressure ridge will produce fine conditions throughout the State on
Sunday and Monday with light to moderate southwest to southeast winds, grading
from mild to warm about southern parts up to hot to very hot in the north and
west.

Cumulative rainfall are forecast to be up to 10 mm over the eastern border
districts as the rain clears today and overnight tonight. Only a few mm is
expected about southern coasts through to midday Saturday. Local falls in excess
of 10 mm are possible with thunderstorms over the Northeast Pastoral district
today and on Friday. No rainfall is forecast on Sunday and Monday.

The outlook for Tuesday, Wednesday and Thursday is for fine conditions
initially. A cold front combined with moisture from Ex Tropical Cyclone Laurence
will cross South Australia on Wednesday and Thursday bringing showers and
isolated thunderstorms.

----------------
US has around 25-50mm again for the south and west. Looks like the moisture should store again for New Years and that could be quite the finale. At least one of these three systems will produce some hefty totals.

Nice to see the BoM going for a wet Xmas Eve. Showers and storms developing Wednesday afternoon.

[johnno]

Hes a optimist that Scott Williams got to give him points for putting it out there this far out good on him.

Be interesting what EC throws up tonight. Will comment later.

[Karl Lijnders]

Well I don't think he is optomistic in this occasion, more reading the play. EC has 40-60mm in the region a couple of days, albeit off and on in it's half runs.

Should be another 10-30mm event, this time maybe favouring C areas.

[Rhino]

EC must be having a sleep in tonights run, has absolutly nothing for the next week for here. Will give it the night off but better have something more pleasing in the mornings run.

Rhino.

[Anthony Violi]

This thread is for the first system, the front with the infeed of moisture from Laurence. Interesting the Bom are going for rain areas, i dont see it personally but i will have a look shortly. I think they will change that tomorrow, but, then again, this is the Bom we are talking about. Infeed is a given, mechanism is what im looking for.

[Karl Lijnders]

Yeah the underlying components are not quite there yet. But things could change as they did with this system. The presence of colder is needed on the western side of the trough or front to really support a thicker and higher rain producing system. Then we also need the front to slow down over the region or cut off into a low with moisture spinning around the region.

At this time, with tonights run, I cannot see it being so dry. But I think we can potentially be looking at more showers and thunderstorms ahead of a change with 10-15mm of rainfall likely. Again things may change...

[Anthony Violi]

None of the models give me any reason to think we will get more than patchy activity at best...early days though and hopefully next 2 or so days and the models will start to give the change some oomph. Which would be a shame as there will be stacks of moisture about and one thing we havent had for a while is deep surface convection.

[Rhino]

Have to say I'm with you Anthony, will be a little rain about but at this stage can't see much in it. BOM still going for rain areas on Thursday but we are, in all honesty, around a week from this event occuring so things will change in that time. Would'nt be surprised at all if everything slips into place and we end up with a good drop before xmas. EC giving at least something for here for the next week, not like last nights run.

Rhino.

[I_Love_Storms]

I can't really see it as boring as the forecasts have it at this point...although if it is, I predict, as you have just mentioned, we will get another very hot, dry, windy day around the 28th-29th, often happens when we have moisture up north on both sides.

[droughtbreaker]

Models are all over the place. GFS has next to no rain for the entire period. EC holds with the Christmas eve rain band. GFS sends the cyclone remnants right down here sometime towards the new year and a massive cut off heading in to the SE. EC doesn't want a bar of that and is probably hinting more towards intense heat but also with some storms possible. I really don't know though it is a mess atm. Day by day prospect at this stage

[Anthony Violi]

Yes models showing great divergence atm...great example of what cyclones do to models given there is much less info in the memory bank on cyclones.

Front looks a little better today but the infeed is only just ok, repeat of yesterday of 10mm at best unless things go our way which they may well yet. GFS doesnt even have a change really so that shows you what they are trying to deal with. Might well be one of those ones that the models dont pick well until 48 hours out.

[Petros]

I can't really see it as boring as the forecasts have it at this point...although if it is, I predict, as you have just mentioned, we will get another very hot, dry, windy day around the 28th-29th, often happens when we have moisture up north on both sides.

Yep ILS - theres too much in the brew to convice me that its going to be boring from mid next week and the 7 days after as well.

Model consensus shows a change rolling through Christmas Eve/Christmas Day, some models capture WA moisture providing plenty of rain, others, just a std cool change.

It wont be a scorching Christmas, and possibly a period to test those in tents out our way (Lakes Entrance etc.).

[Pengaz]

Bring on a humid wet stormy christmas i say. Last time we had a stormy christmas day out this way was back in 1998, which coincided with the intense low pressure system that smashed into the Sydney to Hobart yacht race.

Couldnt agree more-despite the models being a complete schmozzle at the moment, the presence of the cyclone lingering all week and an intercepting trough is enough to get me hooked. Will be watching this one closely, for christmas' sake.

Another 10-15mm fall like yesterday and we'll be laughing Petros. Throw in a few rumbles and than we'll definitely have to have an extra beer (to ackowledge appreciation)....

[Jake Smethurst]

Not sure how to take this one really. Models all over the place because of the cyclone, but something has to happen with all the moisture floating around the continent at the moment. It's a day by day thing really at the moment.

[Dc449]

Will this weather?? effect the Boxing day test in anyway?

[Anthony Violi]

I still dont see anything i like with this system....yet. Could change as EC have the front a fair bit stronger the last 2 runs so the promise is there. Infeed will not be a problem at all, i just hope its not wasted this time round. Reason being is there is no gaurantee for a system of any substance when the cyclone makes a move SE later in the run. So would be good to cash in next Thursday.

[Anthony Violi]

Btw looks like a good system for NSW...and also could be a hot spell before New years..

[Karl Lijnders]

Well looks like there is a good consensus of having 10-20mm across the region. Plenty of humidity coming in from all angles and we could see a similar fall to last Thursday. That would be a fantastic effort.

40mm out of the infeed bands out of the cyclone is very normal.

Wednesday could see the risk of a shower or thunderstorm later.