Author Archives: Harley Pearman

Major rain event, storms and floods Eastern Australia – 24 to 26 November 2021

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A number of rivers across inland New South Wales are in flood following 3 days of rain, storms and heavy downpours. At the time of writing late Friday, the following rivers or areas of New South Wales are experiencing some degree of flooding:-

1 - Breeza Station - (NW Slopes and plains) - Major flooding.

2 - Kingdon Ponds at Scone - (Upper Hunter) - Major flooding.

3 - Musslebrook - (Hunter River) - Moderate flooding.

4 - Wee Waa region - (NW NSW) - Major flooding.

5 - Gunnedah - (Namoi River) - Moderate flooding.

6 - Tamworth Road Bridge - Peel River - Moderate flooding.

7 - Mendoran - Castlereagh River - Moderate flooding.

8 - Goondawindi - Near Queensland border - Moderate flooding.

9 - Molong - Molong Creek - Major flooding.

10 - Jemalong Weir - West of Forbes - Major flooding.

11 - Wellington (Bell River) - Moderate flooding.

12 - Boggabri - Namoi River - Minor flooding.

There are other rivers of concern including Darlington Point (Minor flooding) and at Jingellic (Above Lake Hume) - Minor flooding.

Three days of rain, much of it heavy falls have affected large swathes of eastern New South Wales / Victoria / Queensland and even the Australian Capital Territory.

The result has been a very wet November with rainfall being well above average. This is also being accompanied with cooler than average daytime temperatures as thick cloud cover has been persistent.

 

For example, it has not reached 30C once this month in Blacktown where I reside, with the highest daytime temperature being just 29.4C being recorded on the 19/11/21. So far, it has rained on 13 out of 25 days this month where I live with thunder being audible on 4 of those days.

Some of the rainfall has been significant as follows:-

1 - For the 24 hours to 9 am 23/11/2021.

Eastern Queensland - Widespread falls of 100 mm plus impacts large areas north of the Sunshine Coast including:-

Pacific Haven - 113 mm.

Leesons - 110 mm.

Childers South - 109 mm.

Miami - 105 mm.

Eastern New South Wales

Dorrigo - 140 mm.

Delward - 137 mm.

Bellingen - 100 mm.

Such rainfall has caused waterfalls on the Dorrigo Road to flood across the road linking Dorrido with Bellingen.

2 - For the 24 hours to 9 am 24/11/2021

Parts of North Eastern Victoria is drenched with falls of 26 to 43 mm occurring including the area around Bright and Myrtleford.

Upper Buckland receives the heaviest total of 48 mm.

Across the border in New South Wales, a very isolated fall of 60 mm occurs at Portable.

3 - For the 24 hours to 9 am 25/11/2021

Narrandera in the Riverina region receives 72 mm including 61 mm in 9 hours. Such a fall is rare given the location and climate.

Barellan receives

59 mm and Yanco receives 53 mm.

Jingellic receives 67 mm and Tumbarumba receives 58 mm.

Evening rain and embedded thunderstorms result in an isolated heavy total of 96 mm at Warragamba Dam in Sydney’s outer west. Sporadic lightning is also observed to the west during the evening

4 - For the 24 hours to 9 am 26/11/2021

Rainfall is widespread with some of the heaviest totals being:-

Mount Palmer - 117 mm.

Kars Springs - 115 mm.

Blackville - 111 mm.

Bundella - 106 mm.

Boomera Creek - 104 mm.

All locations are within a small area of the Upper Hunter and lower North West Slopes and Plains.

Kapooka (Just to the south west of Wagga Wagga) - 71 mm.

Following a humid and cloudy day Thursday, heavy rain moved into Sydney. A heavy downpour occurred at Blacktown and as it passed over, rumbles of thunder began to be heard. I managed to take photos of the cloud tower and its base only after it had cleared to the east. The thunderstorm was embedded within low cloud making it hard to identify. As the low cloud broke apart, the cloud base and parts of the updraft tower became more visible allowing me to obtain a few photos in very difficult conditions.

Much of Sydney was impacted by between 25 and 48 mm with much of this falling from that Thursday afternoon event especially around Blacktown - Seven Hills and the Parramatta region.

Cumulative rainfall totals have been significant with large regions of the state impacted by falls of greater than 50 mm with some areas north of the Hunter Valley being impacted by upwards of 200 mm.

While the worst of the wet weather has passed for the immediate period, further shower activity is expected over coming days.

Attached to this post are:-

1 - Himawari satellite images showing cloud cover impacting eastern Australia.

2 - The BOM radar image of the thunderstorm cell that impacted much of Western Sydney Thursday afternoon.

3 - Cumulative rainfall for the seven day period to 9 am 26/11/2021 for New South Wales.

4 - An image showing typical rain falling.

5 - Three images of the storm cell taken in difficult conditions with just enough time available during a break in the low cloud cover.

6 - Sydney rainfall for 26/11/2021 showing the spread of rain across the city.

Rain, storms and flooding – New South Wales – 20 to 22 November 2021

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During Saturday afternoon, the first showers of rain arrived across Western Sydney. There were no thunderstorm events but the showers later tended to light rain that was sustained overnight Saturday and throughout Sunday.

Sunday in Sydney was a cold day with constant light rain falling and maximum temperatures struggled to reach 20C. Generally, maximum temperatures reached 17C to 19C across the city which is more typical of a winters day.

Rainfall totals for Sunday to 9 am 22/11/2021 across Sydney fell between a range of 5 mm at Sans Souci to 33 mm at Avalon Beach with falls of 10 to 20 mm being widespread across the city.

Across other areas of the state, rainfall became heavy especially across the north west slopes and plains and thunderstorms added to the figures that fell.

For the 24 hours to 9 am 21/11/2021, the heaviest falls were:-

Macintyre River at Wyoming - (NW of Armidale NSW) - 72 mm.

Gred - (Kings Creek) - 70 mm.

An area south west of Glenn Innes received between 50 to 72 mm.

Other falls of greater than 50 mm included Bendemeer (NE of Tamworth) - 55 mm and Uralla - 22 km south west of Armidale - 52 mm.

There were also falls of 50 mm around the Port Macquarie region on the mid north coast.

While this rain occurred, the south west portion of the state remained under clear skies for the day as shown on the Himawari satellite image.

For the 24 hours to Monday morning 22/11/2021, heavier rainfall occurred which included falls of greater than 100 mm at some locations including:-

Mt Seaview - 122 mm.

Carrobrook - 109 mm

Bundarra - 102 mm.

Such high rainfall totals were limited to the Musslebrok region and a small area inland from Port Macquarie. The 100 mm plus fall at Bundarra north / north west of Tamworth is an isolated heavy total of greater than 100 mm.

Widespread falls of 25 to 50 mm fells across the north west slopes and plains, the Northern Tablelands, the Hunter region and the Mid North Coast. Several locations received heavier totals of between 51 and 99 mm across the same regions.

This has been enough to exacerbate the flooding situation with moderate flooding occurring around Tamworth (Paradise Weir) and now major flooding at Breeza Station - Mooki River.

Moderate flooding has also occurred around Musslebrook (Hunter Valley) and at Mandoran (Castlereagh River) south west of Gunnedah. Major flooding is still occurring west of Forbes with moderate flooding still occurring at Forbes.

Another rain event is expected on Wednesday that has potential to worsen the flooding situation across the state. Forecasts are being made for 50 to 75 mm to fall across most of Eastern New South during the next 3 or 4 days and thus the flooding situation is likely to worsen especially for those catchments that are now saturated.

Another November Rainfall event for NSW – 19 to 22 November 2021

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Following on from the recent rainfall event which has caused moderate to major flooding along the Lachlan River around Forbes in the Central West of New South as well as other concerns of saturated catchments along some river catchments across the state and Eastern Victoria, another rainfall event is now looming.

This event is of concern and while models are varying again as to who would be receiving the higher totals, there is general consensus that Eastern and south eastern New South Wales would be receiving the higher totals.

If the models are accurate then:-

  1. The Central West area focusing on the towns of Forbes / Young / Bathurst / Mudgee regions.
  2. The south coast focusing on Nowra / Ulladulla and Batemans Bay.

Could potentially experience the higher rainfall totals.

However, some models have also suggested the Upper Murray Region above the Hume Reservoir to experience a significant event for Sunday and thus is another area to be watched.

This event also has potential to impact Sydney on Sunday.

It is becoming clear that Eastern and Southern areas New South Wales will be impacted by this event. Should it occur across the Central West as suggested, then it will have potential to exacerbate a serious flooding situation along the Lachlan River. The flood levels of Wednesday afternoon 17 November at Forbes is attached to show what the concerns are.

Rainfall totals of greater than 25 mm are being forecast across large areas of Eastern New South Wales with higher totals of 100 to 150 mm being made for the Ulladulla / Batemans Bay region. Models are also showing 50 to 75 mm for the Sydney region although that is not being reflected in actual forecasts being made on Sunday for the city.

Flooding risks do exist along several inland rivers as catchments are saturated from recent rain and storm events.

Further flood risks also exist along the Gwyder / Macintyre River especially given that a smaller flood is currently passing along tributaries of the river system east Mungindi.

In addition, the Upper Murray region is also wet and with the Hume Reservoir at 97% capacity, a flood threat also exists along this river although releases are being made to create spare capacity.

Burrendong Reservoir is at 128%, Chaffey and Wyangala are at 101% and Burrinjuck Dam near Yass is at 98%. This shows that some of the larger dams in the state do not have much spare capacity to handle another major rain event.

Whatever occurs, this is one event that will be watched with interest by authorities due to the flood risk that exists.

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