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#121636 - 01/08/2006 03:22 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
--- Offline
Member

Registered: 21/04/2006
Posts: 1633
Well... this upcoming weekend marks the 20th anniversary of Sydney's WETTEST DAY EVER: 327.8mm for the 24 hours to 9am on the 6th August 1986.

I'm sure countless people vividly remember this event... how I wish I was around to experience such an infamous meteorological event!!!

ECL's derive much of their energy from the warm waters of the Tasman or Coral Seas. The same waters provide a source of moisture for often intense rainfall, far exceeding that normally associated with cyclones outside the tropics. Such an event, in August 1986, was responsible for Sydney's HEAVIEST 24 HOUR RAINFALL ON RECORD.

The winter of 1986 in Sydney had been the driest in almost a century, and with the bushfire season around the corner, rain was an urgent necessity.
Early on Monday 4th August, light rain began to fall. This rain became heavier overnight, and heavier still next morning. The rainfall reached a peak in intensity between midday and 3pm on the Tuesday, when 100mm fell in the three hours.

Rain continued through the evening, finally easing by around about 2am on the Wednesday. The 24 hour rainfall total to 9am Wednesday was a RECORD 327.8mm... and even in the normally drier western suburbs, totals exceeded 250mm.

The torrential rain created chaos. Flooded roads prompted many motorists to abandon their cars, bus services were severely disrupted, and trains were halted due to flooded tunnels. Many people, faced with difficulties and danger in getting home, stayed in the city that night. In the western suburbs, creeks rose rapidly and flooded houses.

Tragic drownings occured. However, rain wasn't the only dilemma: on Sydney Harbour, strong winds and poor visibility seriously disrupted ferry services. Gales swept the coast, and further south, huge seas created significant problems for shipping off the Illawarra coast.

The rain eased in SYDNEY as the winds shifted more S early on the Wednesday, but this shift in wind direction exposed the southern escarpment of the Blue Mountains to heavy rainfall. The result was one of the largest floods ON RECORD for the Cox and Grose rivers.

Heavy rain extended south to the Illwarra escarpment west of Wollongong, an area accustomed to heavy rainfall from ECL's. But on this occasion rain falling on the Georges River catchment added to already high water levels from rain in the Sydney Metropolitan area. The resultant flood covered the bridge at Milperra and cut the Hume Highway. Rains spilled west of the Divide, with the Macquarie breaking its banks at the Bathurst.

What an infamous and remarkable event it was!!! ... and here are the weather maps leading up to the event, during the event and also the aftermath, courtesy of http://cires.colorado.edu/ and Keith Barnett:

3rd August:



4th August:



5th August:



6th August:



7th August:



8th August:



...and some intense upper level (500 hPa thickness) maps too... notice the insane cold pool that lingered over the Northern Inland of NSW throughout much of the event:

4th August:



5th August:



Looking forward to much discussion re memories, analysis, stories etc re this event... SYDNEY'S WETTEST DAY EVER: 5th to 6th AUGUST 1986.

Steve

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#121637 - 01/08/2006 06:41 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
floody Offline
Weather Freak

Registered: 18/07/2006
Posts: 368
Loc: Bowral
The most dramatic effect of the rain was flooding and while there was some on the Hawkesbury, the most dramatiuc was along the Georges.

For those of you who live in the Bankstown area of Sydney, the local paper is doing a supplement on the floods that the SES has organised. There will be photos. There will also be displays in Fairfield and a business brekfast to educate business owners about flooding on Tuesday 8 August.

The 1986 flood was a 1 in 20 or 5% annual exceedence probability (AEP) event. Interestingly another flood, almost as large occured just 2 years later. Since then there has been no flood of substance along the Georges River.

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#121638 - 01/08/2006 06:59 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
BOM99 Offline
Weatherzone Addict

Registered: 23/08/2004
Posts: 4645
Loc: Australia
This is an event I will never forget either, I experienced what happened from the Bathurst, Lithgow side. During the afternoon Monday 4th in Bathurst it got exceptionaly dark after rain began in the morning. At around 3pm I began to see the odd large fat snow flake mixed in with the heavy rain at work in Bathurst. At that point I realized that I must head home to Sunny Corner before the road gets completly impassable from snow. I remember the drive home, paddocks were flowing in sheets of water and covering parts of the Great Western Highway. Then driving up the hill to Yethholme I was already driving through at least 10cm of snow covering the highway around 4pm. I remember basically skidding my way up with the car twisting sideways, I got up that last hill by the skin of my teeth. Then the drive to Sunny Corner was a sureal sight, the country looked like Switzerland in winter I have never seen anything quite like it since. At Sunny Corner the house I was staying in was leaking water through the ceiling due to snow blocking all the gutters. As I left the house to stay with the owners up the road, huge branches were crashing to the ground snapping under the weight of snow. Then we watched what was happening from the owners house, snapping cracking sounds continued for hours after that as every tree in all the forests shed huge limbs from the weight of snow. The snow continued to fall until a little after sunset and I estimate that it fell at around 0 to 0.5 deg. Through the night the temperature began to rise and the wind began to pick up from the SE. I stayed in Sunny Corner the next two days with friends, all the power was out and the devastation was amazing. For many years to come I could see all the trees that were affected by snow damage. The devastation was very widespread since Cherry Tree Hill on the Mudgee road also had snow damage visible for a few years.

I wrote a letter to BOM afterwards explaining to them that the exceptional flooding was not just a result of rain, but also the snowmelt combined with rain since that following night heavy rain pounded the heavy snow multiplying the runoff. This fact was so overlooked in any descriptions of this event afterwards so it needs mentioning. The following 2 days there was still the odd sleet mixed with drizzle in strong SE winds after the rain eased.

An interesting thing to realize is also that only 10 days earlier on 25th July a very unusual cold dry change brought snowflakes to the North shore of Sydney, a brief afternoon blizzard to Bathurst and the coldest cold snap in my memory across the CT's, water pipes frozen/broken etc.

Also it should be noted that unlike Sydney the winter of 1986 was not a dry one in Bathurst and Sunny Corner in particular, it was a winter marked by many heavy exceptional snowfalls. Large numbers of consecutive days with below 10deg Max in Bathurst, including a Max of 3.0 on 9/07/86 which was the 3rd lowest in the 20th century. In early July there were consective freezing days in Sunny Corner with dry snow covering all the ground.

1986 was a snow winter in Sunny Corner that I would class as either 9/10 or 10/10.

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#121639 - 01/08/2006 07:13 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
TOM1111 Offline
Member

Registered: 27/10/2004
Posts: 2789
Loc: medowie near williamtown-octob...
well i wasnt even born smile

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#121640 - 01/08/2006 09:27 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
Starwood Offline
Member

Registered: 27/08/2001
Posts: 2465
Loc: Blackheath & Gladesville NSW -...
Great thread Stevo !

Interesting to look at the surface charts . Its not completely disimiliar to what the models , paticularily GFS have thrown up over the past few weeks at times.

A pipe dream maybe and a long shot definately , but as we head into August just maybe we have a chance of something remotely similiar ??..............

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#121641 - 01/08/2006 10:50 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
Well, as I intimated on another thread, I was in the thick of it that day. I was working in one of the emergency services on a 7 day night shift. As we commenced work at 11pm the night of the 5th of August, it was already chaotic. I was working in the St George area of Sydney, which encompassed Botany Bay. I remember the rain coming in sheets - sideways - it was awesome. It was a sight to see waves crashing over the road at Dolls Point where normally the bay is smooth enough to ski on.

However, between being in awe of the conditions, there was some hard work to do. Numerous powerlines and trees down, streets flooded, car accidents. I remember it was pretty hairy driving around at that time of night in those conditions. Other than other emergency service vehicles, there was not a single vehicle on the road. It was eerie, as if we were driving through some post-apocalyptic no-go zone. I do remember things started to quieten down come daybreak when we finished at 7am, but it was as if we had been through a wringer!

I know our tropical friends must be thinking - so what? But, it was the closest Sydney has come to experiencing cyclonic-like conditions.
_________________________
The original donut hole

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#121642 - 01/08/2006 13:06 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
The 1st Ben Offline
Weatherzone Addict

Registered: 25/09/2001
Posts: 1191
Loc: Petersham Nth (H); Neutral Bay...
Snowmi,

You mention the 25th July. The Friday. I'm pretty sure that was the same day it snowed very heavily in central Canberra at around noon when the temp was 0C. I think that remains the coldest noon temp ever recorded in the capital. Snow settled right along Lake Burley Griffin (one of the lowest points in Canberra). My mother had to stop driving on Commonwealth Avenue Bridge the snow was so heavy.
The next morning the minimum was -8C at YSCB. I remember the winter of 1986 as incredibly snowy in Canberra. One 3pm forecast was "snow showers, mostly about the ranges". Not "showers, falling as snow about the ranges". It was outright "snow". If there's precipitation anywhere in the metro it is going to snow. Very rare in Canberra. I'm going to dig out my old rainfall figures from 1986 at home tonight to see how much rain I got in the first week of August (Red Hill). I have absolutely no recollection of any significant rain at that time but I was 2.5 months out from the HSC so I may have suppressed it, LOL!
_________________________
(H) Petersham (North), Inner West, Sydney. Rainfall YTD 474.5mm (2016: 1296.2mm)

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#121643 - 01/08/2006 13:50 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
BOM99 Offline
Weatherzone Addict

Registered: 23/08/2004
Posts: 4645
Loc: Australia
I had a look at BOM's data for Yass, (for some reason I cannot seem to pull out Canberra's rainfall from their website)

You can get some excelent data from here

http://www.bom.gov.au/climate/change/datasets/datasets.shtml

anyway Yass's data is this

19860804 19860804 0.0
19860805 19860805 9.0
19860806 19860806 0.2
19860807 19860807 0.8

This really suprises me that Yass largely missed out on this rain, yet the CT's did very well.

Ben-1st,
Let me know how Canberra went, but if Yass was correctly recorded it may be simmilar?.

On July 25th, I was at work in Bathurst and watched a wall of snow move over Bathurst like it was a dust storm just after lunch, almost imediatly snow dust was blowing on the roads and the temperature was freezing. However it was all over on 30min with very clear cold afterwards.

Data for Bathurst Ag....

Max temps
Fri 19860725 19860725 4.8 (prior to change)
Sat 19860726 19860726 8.0
Sun 19860727 19860727 4.5

Min temps
Fri 19860725 19860725 4.2
Sat 19860726 19860726 -7.5 - 0.6mm to 9am
Sun 19860727 19860727 -7.0

This far from a very snowy cold snap, but the coldest cold snap that I can remember at any time in the last 30 years.

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#121644 - 01/08/2006 15:02 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
Andrew Miskelly Offline
Weatherzone Webmaster

Registered: 15/11/2001
Posts: 3149
Loc: Mittagong, NSW
Yass' numbers are consistent with the synoptic pattern. The following indication of the rainfall spread - 24hr to 9am - on the 6th may help.



Contours are 10, 25, 50, 100, 200mm.

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#121645 - 01/08/2006 15:18 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
BOM99 Offline
Weatherzone Addict

Registered: 23/08/2004
Posts: 4645
Loc: Australia
Thanks for that Andrew, that makes sense now. A very concentrated event indeed, I can see that 100mm+ region at Sunny Corner and over much of the upper Turon catchment as well, yet Blaney west of Bathurst was almost clear of it and Cowra was clear of it.

I imagine the rain may have gradually moved north the following day but getting less.

Would you have a map of rainfall for the whole month of August 1986 for NSW?.

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#121646 - 01/08/2006 15:53 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
eternal rain Offline
Member

Registered: 10/07/2004
Posts: 5685
Loc: the great sydney desert
Wow, thanks for that Andrew, was just thinking today about what the rainfall map might've looked like for that day and there it is right in front of me smile , good work.

Looks like that rain had no problem reaching the catchments with 200mm+ falling there laugh .

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#121647 - 01/08/2006 16:45 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
kizz Offline
Weatherzone Addict

Registered: 11/02/2002
Posts: 2202
Loc: Beacon Hill, Sydney 152m asl
I remember those two events very clearly.

July 25th was a Friday and the preceding days were WARM. I think it was the day before had a near record warm minimum for July. Then of course there was the cold change. I remember seeing huge banks of clouds rolling over the ranges with dense white curtains of snow drifting over the mountains.
Then getting home listening to talkback radio with mum and hearing all the people call in with snow at Engadine and God knows where else. It was about 7 degrees in Sydney by 3pm or something. Obs Hill recorded 3 degrees the following Sunday and Richmond -6 degrees.

Then less than two weeks later the rain event of my life (so far). I had Tuesdays off from university and remember trying to study that day. Could not believe how heavy and how consistent it was. It did not let up and the winds would shift from strong onshore to strong offshore during the heaviest downpours. I remember this as my desk was next to a west facing window which was open when the wind shifted west in a particularly sharp torrent of rain - soaking all my lecture notes.
Again that was a case of listening to the radio and the ever increasing magnitude of the disaster as reports of fatalities started. You could not keep up with all the reports coming in.
_________________________
PWS
AWEKAS
WOW

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#121648 - 01/08/2006 18:36 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
hail Offline
Weatherzone Addict

Registered: 25/06/2001
Posts: 1496
Loc: Schofields
Hi Kizz,

Not much to add to this event - I am glad you mentioned the -6C for Richmond as this must be the coldest or one of the coldest mornings since the record set in 1970 - yes??

I do recall my lift from school was late - very late in fact - I thought I had missed the lift. No matter which road he went through, the roads were impassible in the Toongabbie region. My brother on the other hand was 5 hours late arriving from the city by train. Although the rainfall during the day was very heavy, it was the constant drenching at night that had me awake finding it difficult to get to sleep.

Regards,

Jimmy Deguara

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#121649 - 01/08/2006 18:49 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
Andrew Miskelly Offline
Weatherzone Webmaster

Registered: 15/11/2001
Posts: 3149
Loc: Mittagong, NSW
Whole of August '86. Unsurprisingly it's heavily impacted upon by the one event.

Apologies for the colour scheme. eek Quick and dirty. The only additional contour is the purple 400mm.


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#121650 - 01/08/2006 19:54 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
The 1st Ben Offline
Weatherzone Addict

Registered: 25/09/2001
Posts: 1191
Loc: Petersham Nth (H); Neutral Bay...
Okay, I've dug out my old rainfall records from 1986.
My gauge was in Red Hill. Vancouver Street for those who know Canberra. Just north of Flinders Way.
All figures to 9am on the day in question.
August 4th TCE
August 5th 2.5mm
August 6th 0.7mm
August 7th 5.2mm
August 8th 0.3mm
August 9th 0.2mm

Total for the month 53.0mm on 15 days.

Rainfall to 9am on July 26th was 1mm, which would have been all snow.

Ahhh, memories.
_________________________
(H) Petersham (North), Inner West, Sydney. Rainfall YTD 474.5mm (2016: 1296.2mm)

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#121651 - 02/08/2006 00:59 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
--- Offline
Member

Registered: 21/04/2006
Posts: 1633
WOW!!! eek ... Just goes to show how concentrated the event was- how the event effected such a small area but high in density. What intrigues me is the percentage of the Sydney August 1986 total rainfall that was recorded for the 24 hours to 9am on the 6th. The total for August 1986 in Sydney was 470.6mm and 435.8mm in Turramurra... meaning that a whopping 70% of the month's mammoth total was received in just one day.

Glad to hear about some awesome experiences from the 25th July also!!! That 3 degrees in Sydney would've come marginally close to the coldest temperature ever record, I would assume. Not surprised re -6 degrees in Richmond... the cold airmass associated with the event was extremely intense.

On another note... as much as I want to experience around 13 inches of rain in 24 hours... 6 lives were lost during the floods, in particular through the suburban areas surrounding the Cox and Grose rivers.

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#121652 - 02/08/2006 08:28 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
kizz Offline
Weatherzone Addict

Registered: 11/02/2002
Posts: 2202
Loc: Beacon Hill, Sydney 152m asl
Hail and Steveo,
With regards to the cold outbreak I will have to defer those figures to someone like Blair or Laurier or someone who has access to stats going back that far. I wouldn't mind checking out the previous few days as well to see how high the temperature was.
I seem to remember that the Saturday morning in Sydney was not much colder than 7C as the wind still stirred things up. It wasn't until Sunday when it calmed down that the temps plummeted. Now it has been a while but I also seem to recall that on the Sunday some high cloud moved across in the morning meaning Richmond had a daily range of -6 to 10. A daily average of 2C!!! Sydney managed 3 - 13.
I hope I'm not thinking of another date though shocked
_________________________
PWS
AWEKAS
WOW

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#121653 - 02/08/2006 11:33 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
rain gauge Offline
Weatherzone Addict

Registered: 16/02/2006
Posts: 4556
Loc: Gorokan NSW 4klm West of the ...
i remember that day very well as it was my birthday aug the 5th which is really when most of the rain fell. my sister was living in londonderry just nth of penrith she had a young baby at the time and had to be evacuated by boat as the whole house was surounded by water,and i think 2 young children drowned near oxley park(stmarys) and who could forget the horses stranded near windsor on a bridge i think. i remember someone saying it was a day sydney was not likley to see again aint that the truth. back in those years sydney was a lot wetter allways alot of mud around unlike today where its dust and low flying paddocks.I think the low that day was east of taree.
_________________________
June Rain. 127.5mm
YTD-557.1
2018 rainfall-1125.1mm





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#121654 - 02/08/2006 11:47 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
tomtankman Offline
Weather Freak

Registered: 01/05/2002
Posts: 147
Loc: Neutral Bay, Sydney
SYDNEY 1986-07-28 Min 4.4 Max 12.8
SYDNEY 1986-07-27 Min 3.1 Max 13.2
SYDNEY 1986-07-26 Min 3.2 Max 14.3
SYDNEY 1986-07-25 Min 14.3 Max 15.5


From memory the minimum of 3.2 on the 26th was actually recorded around 3pm on the 25th which was around when melting snowflakes were observed on the North Shore.

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#121655 - 02/08/2006 12:35 Re: 5th- 6th August: 20 YEARS since Sydney's WETTEST day EVER... 328mm
--- Offline
Member

Registered: 21/04/2006
Posts: 1633
Wow!!! Unbelievable... eek ... it's hard to believe that Sydney actually recorded such insane temperatures at that time of the afternoon. Would be awesome if some people had shots of the late July 1986 possible snow event on the North Shore... wouldn't that be an amazing sight. laugh I take it the flakes failed to settle however :p .

Was speaking to my Geography teacher today, and she vividly remembers the August 5-6 1986 rain event in Sydney... she was apparently living in Manly at the time and she recalls storm surges inundating homes and restaurants, alongside the flooding produced by the torrential rainfall. I said that I can't express how much I would've loved to experience such a phenomenonal event... her answer was, "You'll witness some powerful weather events in your lifetime, especially with Global Warming."

Steve laugh

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