Flood E NSW SE QLD East Coast Rain Event 11 Dec - 20 Dec 2020

BrettSS

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Sep 7, 2020
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The water level of Hinze Dam is rising slowly but steadily.


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At 8:37 a.m. today (Monday, December 14th, 2020), the water level of Hinze Dam was 2.32 metres below the spillway, up by 1.20 metres from its level of 3.52 metres below the spillway at 6:30 p.m., Saturday, December 12th, 2020 (just before it began to rise).


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Now (as at 6:30 p.m., Monday, December 14th, 2020) the water level of Hinze Dam has gone up another 54 cm to 1.78 metres below the spillway. So it's risen nearly half of the distance to the spillway from its level at 6:30 p.m. on Saturday (December 12th, 2020), in 48 hours.

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Multiversity

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Jul 29, 2019
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Thanks for this explanation - was wondering about the WV images as well. That precip around thru the afternoon in inner west Bris was really just a light drizzle - I thought it might be forming below an inversion.

Water vapour imagery typically picks up the "tops" of significant moisture in the atmosphere and in practice, it's usually moisture in the mid and upper levels that shows up the best in the imagery. The browns and very dark greys in that particular style of WV imagery typically represent fairly dry air but even in areas of light greys/whites, you can still get showers that are confined to lower parts of the atmosphere (the moisture's reasonably shallow and at lower heights so it won't show up that well on the WV imagery but enough to still allow showers or drizzle to form).
You can clearly see that plume of drier air that's intruded and is swirling around the mid/upper low with more convective weather near the centre of it (usually the case) and deeper convection and rain areas on its outer southern and southeastern flank where upmotion's maximised (again, usually the case with upper lows).
 

Michael Hauber

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Jul 4, 2019
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Hmmm, have to learn the dynamics of Lows' and Vapour images,
This image current vapour I assume dry air 'grey colors' sth of Brizz down to border, yet its still raining here ?
Not understanding this in any way,,, appreaciate any input on this ...
Thnx

qld-wv-202012131330d.jpg

As Ken mentioned it picks up moisture much better in the mid to upper levels of the atmosphere. As these layers are much colder they don't hold nearly as much moisture as the lower levels - saturated air at the mid levels might still be at or near freezing temps, and air at ground level with a dew point near freezing is usually considered bone dry. Cold mid level air with a dew point near freezing may be 100% humid from a relative point of view, but still contains the same amount of water if measured as litres/cubic meter.

Generally the largest amount of moisture is in the lower levels which is not picked up by water vapor images. The most important thing that water vapor images show in my opinion is where air is sinking or lifting. If air is being lifted from lower levels then even relatively dry air (say dew point 10) is going to reach and exceed saturation as it is lifted and gets much cooler. In contrast if the air is sinking then the air is from even higher levels where the temp may be 20 degrees below freezing so its going to be exceptionally dry. So generally wet areas on a water vapor image show areas of broad scale lift. This will mean that at lower level air will be converging and bringing in extra low level moisture to replace the air lifted up. dry areas are broad scale sinking air and tend to correspond to divergence at lower levels.
 

Ken Kato

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Jul 13, 2019
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Brisbane
Generally the largest amount of moisture is in the lower levels which is not picked up by water vapor images.
You can sometimes see particularly striking examples of that on otherwise sunny thunderstorm days when you have a moist boundary layer but it's dry above it. These areas appear as quite "dry" in WV imagery because the moisture is in the lower levels but all of a sudden, big blotches of moisture explode in these areas associated with Cb's (with their moisture being rooted in that moist boundary layer) mushrooming up into the upper levels.
 

Flowin

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Jul 5, 2019
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Pinjarra Hills, QLD
[QUOTE="Ken Kato, post: 4522044, member: 71251....even in areas of light greys/whites, you can still get showers that are confined to lower parts of the atmosphere (the moisture's reasonably shallow and at lower heights so it won't show up that well on the WV imagery but enough to still allow showers or drizzle to form).
You can clearly see that plume of drier air that's intruded and is swirling around the mid/upper low with more convective weather near the centre of it (usually the case) and deeper convection and rain areas on its outer southern and southeastern flank where upmotion's maximised (again, usually the case with upper lows).[/QUOTE]

I am glad we are getting some stratiform rain, because our parched landscapes need it particularly in areas that have not got much from the convective rain.
 
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James Dun

Hard Yards
Sep 15, 2019
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Piggy in the middle at Morayfield. That storm offshore that came down from near Fraser Island towards me died over Bribie Island and then probably set off that new storm that's just formed near Narangba haha. Should be a good drink for the north-western suburbs. Certainly been a welcome change watching all the activity on the radar over the last few days :)
 

Slovenski

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Jun 7, 2019
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Mount Hallen
Great day today, havnt been reading the forum today, up to 70mm event total so far & still raining atm.
Cruiser got a good wash today driving to Coolie & back. Observed the natural big washing machine on some of the beaches.
Event not over yet I suspect.
Wow, lightning, coming from the E.
Very unusual.
 

Mezo

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Dec 11, 2019
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Springfield
Sitting on 141mm since Friday here after another 59mm since midnight. Still more showers and the odd embedded storm coming through.

Very happy with my lot. Was hoping for something on par with the October event, have just about doubled that. It's been lacking a bit as far as extremes go due to the lack of embedded storm activity. But, the lawn and garden will be very thankful. Will be good to see the greater landscape green again. Was getting sick of looking at a dry tired mess.
 

Falling_Droplet

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Jul 7, 2019
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Ferny Grove, QLD
fernygroveweather.com
I had been longing to see some decent activity, so this has great to see. Hopefully the start of much more favourable weather in the coming months. I wouldn't have minded getting a bit more severity in the weather than I had (not helped by the fact I am a bit sheltered from the south), but this is so much better than most of the season so far.

Monthly rainfall total is 123 mm so far, which for here is the highest since 131.6 mm in 2011, and the highest since 198.2 mm in 2010 if I only count the first 15 days in past Decembers.

Some further light showers in the late afternoon that cleared at 6:45pm. The remnants of a thunderstorm that weakened into a shower is now approaching from the north-east as most of activity passes to the north-west. In the past few hours the temperature have been falling slowly and have been close to average. Dew point is remaining slightly above average while falling slowly. Relative humidity have eased from very high to moderately high that rose a little in late afternoon and early tonight before stabilising at 97%. Wind have been light S to SW with periods of calm winds that were followed by calm winds in the past hour.
 

Flowin

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Jul 5, 2019
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Pinjarra Hills, QLD
I dunno how to describe the composite sat Water vapour image, radar, lightning image below.

My attempt to describe it is an upper low WV (yellow guess) grabbing a surface trough (blue guess) and dragging it inland. My guesses may be wrong though as I am my expertise is limited. If I am halfway on the money, I am glad I have witnessed a “a good catch” between uppers and lowers.


4D20F65E-7513-4E9B-8180-C593834B258E.jpeg
 

Seabreezes

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Jul 4, 2019
439
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South West Rocks, NSW
52.8mm has fallen since 9am. Steady to moderate rain, tending very briefly heavy at times, began falling during the day and continued into the evening. The rain has since cleared though a constant drizzle has persisted.
Expecting rain/showers to redevelop here about the local area by morning. Not clear on how much heavy stuff we'll get right here, but that potential should become more evident by morning too.

Minor to Moderate flood warning has now been issued for the Nambucca River: http://www.bom.gov.au/nsw/warnings/flood/nambuccariver.shtml

And also a Minor flood warning for the Richmond River:
http://www.bom.gov.au/nsw/warnings/flood/richmond.shtml
 

PlumbBob

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Jul 5, 2019
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Molendinar
As Ken mentioned it picks up moisture much better in the mid to upper levels of the atmosphere. As these layers are much colder they don't hold nearly as much moisture as the lower levels - saturated air at the mid levels might still be at or near freezing temps, and air at ground level with a dew point near freezing is usually considered bone dry. Cold mid level air with a dew point near freezing may be 100% humid from a relative point of view, but still contains the same amount of water if measured as litres/cubic meter.

Generally the largest amount of moisture is in the lower levels which is not picked up by water vapor images. The most important thing that water vapor images show in my opinion is where air is sinking or lifting. If air is being lifted from lower levels then even relatively dry air (say dew point 10) is going to reach and exceed saturation as it is lifted and gets much cooler. In contrast if the air is sinking then the air is from even higher levels where the temp may be 20 degrees below freezing so its going to be exceptionally dry. So generally wet areas on a water vapor image show areas of broad scale lift. This will mean that at lower level air will be converging and bringing in extra low level moisture to replace the air lifted up. dry areas are broad scale sinking air and tend to correspond to divergence at lower levels.
Awesome explanation Michael, I get the jist of that, makes a lot of sence, air is cooler with hieght - knew that one, check.
Dew point varies with hieght although a value off near 0 on the ground will be far different to a value of 0 in the mid levels because the amount of water as litres per cube changes due to temperature being cooler the higher it is.
Still need to rethink the Lifting and Sinking dynamics, quite a numbers game over all, but the principles is the same !
I like the way you explain it better, infact I have copied that for the 'files folder' cheers
 

Auzza

Addicted
Nov 12, 2019
50
341
133
Grafton, NSW
142mm in the last 36 hours to 9am here bringing us to just over 260mm event total. Total will probably be a couple mm higher in 5 minutes but it's too heavy to go outside and check atm. Lot's of water pooling around town, rain has been on and off very heavy since 6am. Grafton Research station recorded about 25mm in the last half hour.
 

Falling_Droplet

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Jul 7, 2019
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Ferny Grove, QLD
fernygroveweather.com
The temperature fell very slowly in the early hours and was slightly warm before returning to near average this morning as the temperature rises. The temperature this morning is 0.5 C below the maximum yesterday, so yesterday maximum temperature looks likely to this morning maximum temperature until 9am. Dew point fell very slowly before rising this morning and have remained slightly above average. Relative humidity have been close to average and was stable and close to saturation in the early hours and early this morning reaching a maximum of 99% for nearly 2 hours. This morning the relative humidity have dropped slightly. Calm winds today, except for some SW breezes this morning.
 

Rainbomb

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Dec 3, 2019
122
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Caboolture
Quite an underwhelming rain event personally here for north Caboolture. 115mm since Friday almost the same amount of rain during Monday's 4 storm afternoon (106mm). Rain rates of mostly 5-20mm/h caused little excitement for this event.... Other than this current heavy shower that pushed the peak rain rate to 104.8mm/h.
 

Bello Weather

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Jul 12, 2019
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353mm in town this event so far. Current rain rate 53mm per hour, with 28mm since 9am this morning...definitely in that favourable south easterly quadrant of the upper low. Here's how three of the local bridges currently look:

brierfield.jpeg
lavenders.jpeg
moodys.jpeg


Yes, that middle shot is of the main bridge through town. Rivers here rising very quickly at this time...I've got a summary of them on my website. you can see the Bellinger at Thora heading towards Major - though will need the rain to continue for some time to get there.
 

Ken Kato

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Jul 13, 2019
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Brisbane
Sun out here this morning, total of 258mms thus far. BOM has 10 - 20mms each day till Thursday, is this still coming from a combination of the UL and easterly flow? And has the surface trough shifted south as the main cloud runs parallel to the GC and turns in on the mid to north NSW coast?
The more favourable (for widespread rain) outer southern and southeastern flank of the upper low is now down around the MNC and areas to the adjacent southwest where some rain areas are occurring and the upper low itself is also starting to gradually lose strength. There's also a localised surface trough near the northern part of the MNC which is helping to enhance the rainfall near that area.
There's still some background upper support from the upper low and we're in the deep NE to N flow on its eastern side but most rainfall over the next several days for SEQ should be more in a convective mode with no strong focal points i.e. day after day of a humid northeasterly flow, a mix of sun and clouds, and some sporadic shower/storm activity that can pop up at any time of day or night. But since the vertical wind profile has become a bit more conducive to training, any locations which get under a narrow heavier train of convection could get hefty rain rates.

In other news, here's the "Dorrigo Falls" at the moment:

 

PlumbBob

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Ski Pass
Jul 5, 2019
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Molendinar
Cool Ken !,,, Dorrigo Falls, huge, rippin' water. hope that road's foundations are ebbedded into the rock real well, wont last much longer otherwise ..
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5ks west of Southport GC
Cheap 'tipper gauge' readings collected 126 to Sat morn, then trips a new week and another 206 to this morn Tues 9am
Total = 332mm.

The good ol 'Bucket system' collected 180 to Sun morn, emtied and another 160 to this morn Tues 9am
Total = 340mm.
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Edit - News :
Massive boulders on Mount Tamborine road.

Tambo Mnt Huge Rocks .JPG


And Wappa Dam Spilling SCoast Hinterland
 

Mezo

One of Us
Dec 11, 2019
394
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Springfield
A few more solid showers through here this morning, bringing our event total to 154.4mm

Midnight-midnight totals:
Fri: 0.2mm
Sat: 24.7mm
Sun: 57.1mm
Mon: 65.3mm
Tue: 7.1mm

Lawn now showing signs of fungal damage from being wet for four days. Last week I was struggling to keep it from drying out.
 
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