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#1469928 - 01/09/2018 20:24 SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018
Seabreeze Offline
Weatherzone Moderator

Registered: 18/09/2005
Posts: 10482
Loc: South West Rocks, NSW
A trough will combine with a decent onshore flow to deliver showers, rain areas and possible thunderstorms to SEQLD/NENSW. Rainfall should favour areas east of the ranges. There are some places which could accumulate more than 50mm during the event, which is more than, or close to, the September monthly average in almost every SEQLD/NENSW location.


Edited by Seabreeze (08/09/2018 18:07)
Edit Reason: title edit
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South West Rocks, NSW Mid North Coast:
December 2018 Rainfall: 18.4mm (December Avg. 118.3mm) // December 2018 Raindays: 6 (December Avg. 12.8 raindays)
Year-to-date Rainfall: 1331.6mm (Yearly Avg. 1490.8mm) // Year-to-date Raindays: 129 (Yearly Avg. 137.6 raindays)

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#1469940 - 02/09/2018 07:31 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Steve O Offline
Weatherzone Addict

Registered: 02/03/2011
Posts: 3334
Loc: Beenleigh, QLD
Thanks SB, might be abit of convergence there and looks like a surface low tries to form just offshore. Though starting to see surface winds wrapping up SE'ly.

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#1469941 - 02/09/2018 07:33 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 611
Loc: Pinjarra Hills, Qld
I am hoping to get one shower with enough intensity to wash the new dust off the roof I cleaned a few weeks ago. Was ready to paint yesterday, decided not to proceed when I saw the wind and dust.
Looks also like some chance some rain still around next weekend. Hope the event provides a good few drops say at least 30mm for all that need it.


Edited by Flowin (02/09/2018 07:33)

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#1469946 - 02/09/2018 08:58 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
DDstorm Offline
Weather Freak

Registered: 13/05/2010
Posts: 300
Loc: Tallai, QLD
Nicely started SB, lookin forward to the dust been washed down, much much clearer this morning. Might even get a start to the wet stuff late this arvo.
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#1469951 - 02/09/2018 11:54 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Steve O Offline
Weatherzone Addict

Registered: 02/03/2011
Posts: 3334
Loc: Beenleigh, QLD
Few note worthy things strong mid to upper level shear and a nice area of nicely chilled upper temps as you mentioned earlier.Though don't think we will see much precip until tomorrow onwards.



Also one of the few descent forecast soundings at 18z.









Edited by Steve O (02/09/2018 12:03)

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#1469957 - 02/09/2018 15:09 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
TWEEDSTORM Offline
Weather Freak

Registered: 08/01/2012
Posts: 867
Loc: Tweed Heads NSW
Air is cold, dry and quite blowy down here this Arvo, looking forward to a more moist component from the south east.At least the dust has cleared now all we want is some heavy showers and some rumbles hopefully.

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#1469964 - 02/09/2018 18:54 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Seabreeze Offline
Weatherzone Moderator

Registered: 18/09/2005
Posts: 10482
Loc: South West Rocks, NSW
Today began to feel cool as the southerly wind gained strength (a noticeable change from yesterday's balmy weather). The appearance and increase of lower level cloud later this afternoon signalled that moisture was increasing in the lower levels. Only expected to reach 17C tomorrow around the local centres, though winds should be lighter.
_________________________
South West Rocks, NSW Mid North Coast:
December 2018 Rainfall: 18.4mm (December Avg. 118.3mm) // December 2018 Raindays: 6 (December Avg. 12.8 raindays)
Year-to-date Rainfall: 1331.6mm (Yearly Avg. 1490.8mm) // Year-to-date Raindays: 129 (Yearly Avg. 137.6 raindays)

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#1469973 - 02/09/2018 20:46 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Ken Kato Offline
Meteorological Motor Mouth

Registered: 05/03/2012
Posts: 5619
Just had a good look at this setup and I'm thinking mainly modest falls away from the coast but decent falls along the northern NSW coast and possibly the far southeast of SE QLD with the main peak around Tuesday (but this may change).

Rainfall amounts are always notoriously hard to accurately predict but I feel the majority of inland places will probably stay below around 15mm (although a few could get more under any lumpier convection).... around 10-40mm closer to the coast.... & around 40-90mm along the northern coastal fringe of NSW and far southern coastal fringe/hinterlands of QLD... some places in that latter region might get even more than that. Obviously this won't necessarily all fall over the span of one day.

Dominant weather type looks like mainly showers, tending pretty frequent near the coast by Tuesday.
Some locations could also get some thunder with the modest instability. For some areas where it doesn't become too saturated to depth, some small hail might occur under some of that activity.

Daytime temps look pretty cool by Tue/Wed under the cloud cover also and the breezy conditions on Tue should make it feel even cooler.

If the upper low and trough stay further south than expected, rainfall amounts for SE QLD should be a lot less than currently suggested in this post. If they come up further north than expected (and stay a bit to our west for a bit), rainfall amounts may exceed expectations.
Also, if the offshore surface trough digs in too far south while staying just off the coast, this will deflect the winds to have a more southerly for us so this would decrease rainfall amounts.

Here's a 5-day total rainfall map from the latest EC together with a multimodel graph for Brisbane:



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#1469977 - 02/09/2018 21:51 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
DDstorm Offline
Weather Freak

Registered: 13/05/2010
Posts: 300
Loc: Tallai, QLD
Great stuff thx Ken. Just what the novices need, much appreciated.
DD
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#1469987 - 03/09/2018 06:47 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3461
Loc: Buderim
EC might favor Gold Coast/NENSW more, but GFS and Access look a bit better for Sunshine Coast. I will apply some wishful thinking bias and claim that Access has the advantage of local geography, and that Sunshine Coast usually does well in these types of events and the outcome will tilt more towards Access/GFS than EC. A lot will depend on how strong the high pressure system comes through and how far north it pushes the convergence line/trough.

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#1469988 - 03/09/2018 06:48 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Ken Kato Offline
Meteorological Motor Mouth

Registered: 05/03/2012
Posts: 5619
EC actually has higher topographical and atmospheric resolution than ACCESS-R (and GFS of course) although it remains to be seen which of those models will be closer to the mark.
One possibility is that the Sunshine Coast will be closer to the offshore trough digging southwards so it may get stronger low level wind convergence & enhance the precip. But areas further south are closer to the stronger upmotion on the eastern flank of the upper trough and low. So will be interesting.

P.S. thanks DDstorm


Edited by Ken Kato (03/09/2018 06:51)
Edit Reason: added stuff

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#1469989 - 03/09/2018 07:09 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Snapper22lb Offline
Weather Freak

Registered: 17/02/2015
Posts: 315
Loc: Golden Beach
Indeed! Thanks Ken and others who contribute opinions. We are out here looking forward to your input. I'm batting for the Sunny Coast to cop a bucketing!

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#1469996 - 03/09/2018 08:51 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Ken Kato]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3461
Loc: Buderim
Originally Posted By: Ken Kato
EC actually has higher topographical and atmospheric resolution than ACCESS-R (and GFS of course)


Thanks for that comment. Is it possible that Access may have any local advantage? If not why run it at all? Perhaps being more tuned to atmospheric processes that are important locally - such as the tendancy of ECLs to interact with the Great Dividing range/local coast.

Sunshine Coast does seem to do very well from anything showery on a SE or E wind, especially compared to Brisbane, where I have lived for many years as well, maybe not so much compared to Gold Coast. Often puzzled over why exactly, perhaps part of it is the location of the range. More recently I spotted a high resolution SST chart showing cooler SSTs in Moreton Bay and thought maybe that is part of the puzzle.

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#1469997 - 03/09/2018 09:02 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Ken Kato Offline
Meteorological Motor Mouth

Registered: 05/03/2012
Posts: 5619
ACCESS is based on the UK model but tuned to the Australian region with modifications. It's handy having another model to look at because it adds to the range of available models and gives info on how much agreement or disagreement there is among them. Also, the more models are used, the more accurate a multimodel consensus forecast becomes.

ACCESS-R still suffers from the phenomenon of coastal locking where it has an excessively sharp gradient or cutoff between land and maritime precip overnight but this has been fixed in the current version of ACCESS-C. ACCESS-R can also often be very erratic with TC tracks. Having said that, it's still a very good model with lots of other things.

And thanks Snapper smile

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#1470004 - 03/09/2018 10:34 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
DDstorm Offline
Weather Freak

Registered: 13/05/2010
Posts: 300
Loc: Tallai, QLD
I've just hung the washin out, that should hurry things along.
It's just hovering off the coast, is the wind to southerly off shore to bring it onto land??


Edited by DDstorm (03/09/2018 10:34)
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#1470007 - 03/09/2018 11:12 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Ken Kato]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 611
Loc: Pinjarra Hills, Qld
Originally Posted By: Ken Kato
ACCESS-R still suffers from the phenomenon of coastal locking where it has an excessively sharp gradient or cutoff between land and maritime precip overnight but this has been fixed in the current version of ACCESS-C.


Ken, thanks for your input it is very helpful. Do you know if BoM use the ACCESS-C in the consensus forecast ADFD (meteye) estimates ? I thought ADFD (meteye) was based on the WATL PME (multi-model) with meteorologist judgement being made to adjust the rainfall estimates, but it is not clear to me whether that is using ACCESS-R or ACCESS-C as part of the multi-model inputs?

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#1470008 - 03/09/2018 11:33 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Ken Kato Offline
Meteorological Motor Mouth

Registered: 05/03/2012
Posts: 5619
As far as I'm aware, ACCESS-C isn't one of the models that are included operationally for precip in the ADFD grids but I'd have to check on that. But ACCESS-R and G can be used.
But yeah, the QPF grids displayed in Meteye and the ADFD are a result of the forecasts from the chosen models which are then manually adjusted by the forecaster where required before it goes public. Meanwhile, the chance of rain grids use equations based on the statistical correlation between probability of precip and rainfall amounts, calibrated to past observations and now also factor in the percentage of models going for precip. This is then manually adjusted where required by the forecaster as well.

As a side note, the WATL/PME forecasts now include the EC ensemble (as well as the deterministic EC) as one of the models.

And yeah DDstorm, winds at both the surface and the lower levels are a bit too parallel to the coast at the moment to drive more of the frequent showers ashore.

Mike: One thing I was also going to add was that the shape of the coastline means that the Sunshine Coast faces more perpendicularly to any E or SE flows while the Gold Coast is more at an angle so that may be a factor as well.


Edited by Ken Kato (03/09/2018 11:43)

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#1470010 - 03/09/2018 11:48 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7371
Loc: Maryborough, Wide Bay, QLD
This system looks pretty meh to me. Enhanced coastal showers under a SE stream but not much at all penetrating inland. Also the next front due on the weekend looks like being nowhere near as active as it once did. Oh well, given the current state of things we'll take what we can get I suppose.

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#1470012 - 03/09/2018 12:00 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
Nic_Bri Offline
Cloud Gazer

Registered: 03/08/2016
Posts: 10
Loc: Mt Gravatt East
Just started showering at Archerfield AP

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#1470030 - 03/09/2018 17:19 Re: SEQLD/NENSW Showers / Rain areas followed by Scattered Thunderstorms - 3rd to 8th September 2018 [Re: Seabreeze]
tsunami Offline
Weatherzone Addict

Registered: 06/12/2010
Posts: 1251
Loc: Wynnum SE Brisbane
Im suprised how cold its got.
Temp has plumited
16c now
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Wynnum SE Brisbane

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