Just thought I would start this thread to try and keep away from the CHIT CHAT that is going to get much much worse during this event

Is it to early to call or not.
Well it certainly seems like the Low progged to form over the Gulf near Gove is on its way..
By the Gove radar obs, there are already some serious falls off the Gove peninsular ( CAPE WESSEL)and the water vapour imagery is starting to show some nice convection.
Although the cape Wessel ground observations do not share the same opinion, I would say that the low has not properly formed or is forming east of the weather station

Perhaps one of the first parts of the puzzle is starting to come together on cue.

So another day or so has passed and we're getting quite close to this event starting.

While the details on any particular hotspots are still hard to pick, there are two key things I see with this event:

1) Heavy rainfall is forecast to be quite widespread - almost all of Queensland (except for Birdsville) and NE NSW is in the firing line. This includes parts of N NSW (eg: near Moree, Walgett etc which had major flooding recently). The point here is that should the rain end up falling over such a huge area, it is one of the the worst sorts of catchment priming you can have if you have a follow up rain event in Feb.

2) The rainfall is also spread over many days (and two phases to the event as I think someone else mentioned tonight - though it will feel fairly continuous for most people) so while it does look alarming to see all these 300, 400, 500mm etc accumulated totals forecast on the models, for most areas we won't see these falls occur over 1-2 days. So this should mean that yes there will be significant flooding, and perhaps some big major flooding in a couple of places, but in general there will be more of the everyday moderate to major flooding that happens from time to time.

It's also probably worth noting that we have king tides this week (dropping a bit by this weekend) so that will have some effect on the flood heights in the lower reaches of the rivers once flood waters work their way towards the coast by Wed onwards.

According to the 00Z run of GFS and AA/AR, it has the upper low/trough through southern Queensland retrograding back into NSW - the process of this would be more likely to drag the current developing trough offshore, onto the coast which would certainly begin to push us into the higher end of a potential heavy rain event (ie falls of a few hundred millimetres developing over the coming days). A few points of note between this week and last week is:

- Weaker westerly influence, will allow for more westward movement of offshore systems
- Broad upper system and slightly further away, meaning we have deeper, easterly winds so any showers/rain that occur offshore will be more likely to come onshore (vs last week where most of it went from N to S).

Much higher chance of some solid totals right across SEQ during the next 24-48 hours, particularly if the surface trough does manage to cross the coast (which traditionally gives much better rain events). BUT - EC still seems quite conservative on the rain for tomorrow compared to the other models...but in this case you'd begin to think the other models will probably get this one right, retrograding systems can make things quite challenging and difficult to forecast for.

However - I'm more concerned about what might happen beyond 48 hours - even if we got a few hundred millimetres, apart from the coasts and local creeks flooding, it shouldn't be toooo major (ie mostly the "usual trouble spots" plus a few others - but the Sunshine Coast could certainly be in for a bit more trouble due to last week's rain and appearing to be in a better position for rain/showers/thunder etc). If you click on a forecast sounding for Wednesday it shows a very moist, unstable and wet atmosphere, we see a new (tropical) airmass descend down from the north and that could produce some heavy showers and storms. In fact, the patterns for Wednesday share a few similarities with the March 9, 2001 flash flood event (that had TC 'Donald' cross the coast near Ballina, and then as it moved inland it dragged the trough westwards and brought a different airmass across SEQ. The weak northerly shear pushed storms southwards, while high instability and moisture meant storms developed northwards). This brought a lot of flash flooding to Brisbane. Anyway - that's just one scenario to watch out for.

In saying all this - given the BoM issued an SWW last week, I'm surprised there's not one already out given this rain event appears more likely than last weeks (particularly due to the deeper easterlies helping to push rain across SEQ from offshore).

Still important not to panic or get too worried yet - as we move into the next few days things will no doubt continue to change, and we still need to wait and see if the trough crosses the coast as that is what will help induce a lot of rainfall too as the new airmass comes across.

Yes it is later in the week that worries me, looking at GFS which has the current monsoon burst across the top end deflected to the south east through the east coast of Queensland and ulimately wrapping around a tropical depression on the central to south Queensland coast to push North Easterlies with through the lower to mid levels into south east Qld, and a precipital water totals normally only found in the tropics under monsoonal conditions.

Of note is that Access instead has the monsoon burst continue to travel east into the northern Coral Sea and not worry us at all.

It will be the direction of this monsoonal burst that I will be watching, regardless of whether it takes an identified low pressure system with it or not.

I would expect that having a possible low/cyclone to the north instead of to the south as in Donald would change a great deal about the potential scenario and make it much more of a general flood event similar to 74, or perhaps 92 which was a low pressure system near Rockhampton that moved inland and died but help direct massive amounts of rain onto the Sunshine Coast.

Hello. How much rain could I possibly see here at Grantham this week please?

hi, have a look at jeff's fb page..has some good info with charts & explainations on possible outcome. has a few updates throughout the day. take a look at the rainfall chart he put up around 5.30pm..here's the link:
http://www.facebook.com/pages/Higgins-Storm-Chasing/139175562844906
hope that helps and stay safe.

Stage 2 of this event is the one we should be paying close attention. Stage 1 has been largely a coastal event; however, both EC and GFS are now in agreement with the monsoon low over the NT will be captured by the amplifying of the current upper trough over western Queensland. The import of this is that it will drag huge amounts of tropical moisture to the SE where it will enhance as it nears the coast in which the Tasman high is feeding in its own moisture. The latest weekly tropical note confirms the return of the MJO and its affect on the monsoon trough. Fortunately, prevailing upper westerlies in the Coral Sea might spare us any developing TC in that part of the world from affecting the Queensland Coast. All in all, no need to panic at this stage. The good thing about the monsoon low being dragged SE is that it will not linger and will quickly clear the coast with the upper trough as it finally sweeps out to sea early next week. Here is the relative passage from the WTN to highlight the influence of the MJO:

Well spotted Clem, I too noticed EC picking up the monsoon low (or 'burst' if you could call it...like an injection into the northern end of the next trough traversing the continent from west to east)...very interesting indeed. Will be watching every run closely to see what it does!

Starting to get a little more worried about tomorrow's potential with convective rain. We'll see a moister airmass come through early tomorrow which is likely to bring some deeper instability and with such a saturated atmosphere, there's going to be the potential for some very heavy and slow moving storms around (the types that might give exceptional rainfall like March 9, 2001 or the Lockyer Valley Flood). I guess we'll see what it looks like in the morning - but 'hopefully' it will just remain thundery rain areas and continue to be more an issue over the usual hotspots rather than causing something more dramatic. But anytime when the trough crosses the coast and we receive a change of airmass you need to start getting a little more concerned from experience.

AC

Thanks for that update AC. We'll have to wait and see.

Ok i dont normally get very techie but can someone answer me this and put me on the right track,thanks.

Just a question regarding jeffs video and this cyclone (mesoscale convective complex) if this was to form as the model projects.Is the factor rapid cooling with height ie,what you can see on the MSTAT vapour loop with that cold pool pushing up through central Queensland,which allows the release of the heat of condensation that powers a tropical cyclone.

Can I ask a question of our more experienced people. I've noticed a system building in the coral sea on the MTSAT. With our system pulling so much moisture in, will it affect the track of any systems out there or are they too far away/wrong direction etc?

Hi Steve - I'm assuming you're referring to the "TC" that GFS is forecasting to push into southern QLD/northern NSW? As I mentioned in the other thread, GFS is still the only model doing this (even CMC dropped it in this afternoon's run). If you look at the upper charts of GFS, there's no real meteorological reason for a tropical cyclone to survive like it's forecast to. GFS as the STJ (Sub Tropical Jet) arcing well into northern Australia which captures the system and slingshots it southwards quickly. Typically what happens is once the STJ captures these systems they become quickly entrenched through a mid-latitude trough and absorbed into it (the main exceptions are very large and intense Cat 4/5 TCs, TC Vance in 1999 for example).

All the other models capture this monsoon low/TC too but they have it quickly being absorbed into a mid latitude rain/storm system which would still bring further rain (with possible heavy falls, particularly over inland areas), would still be quite different to the GFS picture.

AC

Lani - we've been watching that too here in the office. The general thought is that since the upper low is continue to drift slowly SW, that the upper level winds will shift more towards the NW overnight (currently NE). This should stop the mid to upper level moisture wrap-around for SEQ - but might not be so good for NE NSW (and possibly while some of the models are really nailing the NE NSW region tomorrow night with a lot of rainfall). I think the main concern tomorrow for SEQ could very well lie in convective rainfall, but we'll see. In the Jan 11 floods, the upper low was to our north, and it feed NE'lies across into SEQ from top to bottom across the atmosphere.

AC

where is this trough that has been talked about that could cross tho coast?

Thanks AC it's appreciated.

The Weatherzone streamlines show the trough close to the coast quite well Squid (the dip):

http://www.downunderchase.com/temp/ObsField.jpg

AC

thanks AC

So, the general consensus is more heavy rain tonight and tomorrow is that correct? And why is the rainfall rate heavier than radar suggests, is it because of low level heavy cloud and moisture obstructing radar images?

some quick clips taken between 3 and 5 pm tuesday 24 jan 2012. Albert river (stanmore bridge Beenleigh) [video:youtube]http://youtu.be/zLbXYBF3-Ec[/video] Curtis falls (eagle heights rd Mt Tamborine) [video:youtube]http://youtu.be/Dl9VWZB5kaQ[/video] [video:youtube]http://youtu.be/CZxU1oUkwHQ[/video] and Clutha creek (intersection clutha creek rd and tamborine/waterford rd) [video:youtube]http://youtu.be/82Q7Nz8SXRY[/video]

http://www.bom.gov.au/australia/charts/viewer/index.shtml

I noticed the last map on Tuesday - that isn't a TC forming is it?

WOW there are some nice totals around crazy stuff!! The scary thing is that EC thinks the worst is yet to come with another large Convergence zone / MCS (Possibly heavier than last night, looks this way) to start developing later on this evening and continue on well into to tomorrow morning.

Thought Id mention today we will be looking to the N/NW (N/NW upper winds) for the action which will most likely be in the form off thunderstorms since we are no longer under NE upper winds associated with the SE Quadrant of the upper low since it has taken a bit of SW treck as AC mentioned last night. NE NSW and the GC will still be under the NE upper winds thus will be receiving rain wrapping back onto the coast. This is still a major threat to SE QLD thunderstorms can dump massive amounts of rain especially if they are slow moving and followed up by several more.

Is this convective activity on the loop now? (2242Z)? Very defined band, which went offshore over my head not that long ago. Went from windy and pouring, to calm and limited precip. Looks to be convective thanks to the recycling intensity.

Another thing, Bellmere Weather shows a surface low right on top of us, with its eastern trough forming what seems to be the boundary of the offshore convergence. (http://www.bellmereweather.net/ChartLocalWind.html) Any discussion is more than welcome.

Some have referred to the 'convergence zone', but I can't seem to see any evidence of convergence in the Brisbane doppler. There is an obvious line where something is happening, which passes pretty much over the radar, and corresponds to the heavy rain. But looking at the doppler radar I can't get any hint of winds converging, but seem to see more of a shear effect with winds on the east side of the line being much stronger than winds on the west.

Does anyone else have any thoughts on whether this is the case, and what would cause it?

Hi Mike,

Having Stronger winds directed into slower winds is a form of speed related convergence, but If you have a look at surface wind streamlines on wz radar or look at surface obs you will see that there is a directional component and infact a surface low located over Rathdowney area. Remember with convergence zones they are just not on the surface either and generally extend throughout the lowers and mids depending on the strength of the upper feature. You also have Temperature and Moisture Boundary's etc which all play there part in forced lifting and convection.

Nicely put Scottie. Just to expand on that - convergence at the surface results in upwards motion because the air can't sink (because of the ground) so it has no option but to rise. When there's convergence above the surface it's going to result in sinking air. The rising air around these systems in the mid and upper levels is caused by a 'pull' from above from diverging air flow or from air of different density being advected over each other (ie warm over over denser cooler air, the warm air rises - if it's moist enough it rains. The classic backing with height wind profile that we see with some of these systems is a perfect example of this warm air advection).

I love that comment Ben! Now that is meteorology folks.
Speed convergence is very significant for Qld. Classic Speed convergence is when surges push up the coast and give heavy falls to NQ. These surges that are essentially stronger winds knocking up against weaker winds give vast uplift and continual ascent and activity.

Anyways, the new ACCESS-R run is very interesting. Even though it has not done that well for today, I still like to see what it is thinking. Looks like NE NSW will get some good activity into tomorrow, 850hPa winds 20-25 knots sounds very good.

The surface obs seem to suggest a surface low / MCS. There is definitely clockwise rotation of the storm cells on the radar. Anyone with greater knowledge please feel free to let us know your thoughts.

Looks very interesting for the monsoonal low heading for us this weekend. No biggie surprise for gale force NW winds across the region....

I do realize I was premature in talking about an MCS got a little excited as the best and worst of us do sometimes, I did forget to say "Developing" as the current EC run at the time was hinting towards this kind of outcome. However if you review the radar loop from this afternoon and take a look up near dalby you will see atleast one surface low spinning up along the troughline. Obs from the area also back this up IMO.

No surface low Scott just backing with height mate seems the area to the northern Downs had stronger upslope and heat today. Tomorrow looks much better for activity.
Nice thread that got going here
Love the OMG outlook GFS has on the TL wish it would hurry up and drop it off into a trough , oh well jumps models for a while

I have started a new thread here for any discussion of the NT monsoon low:

http://forum.weatherzone.com.au/ubbthreads.php/topics/1063985#Post1063985

So what your saying is that the cells heading in a SW direction and getting wrapped/ingested into the system are lower topped thus tapping into steering flow around the 850mb-700mb level, convective inflow if you will. I thought I saw something a little more organized there possibly radar beam/intensities obstructed by topography somewhat.