Category Archives: Floods

Floods and flooding

Rain, storms, heat and wind – NSW – A state of contrasts – 22 to 28 December 2020

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Rain, storms, heat and wind - NSW - A state of contrasts - 22 to 28 December 2020

The Christmas period across New South Wales has seen significant variations of weather ranging from flooding rains to storms to hot dry and windy conditions.

During the period 22 to the 28 December, New South Wales has been a state of two halves with the north and eastern half being saturated with rain, some of which has been significant while the west and south west has been bathed in sunny and often hot conditions.

In particular and just prior to Christmas (22/12/2020), the region surrounding Tamworth and Gunnedah and other nearby towns were saturated with heavy rain with falls of up to 98 mm occurring. Much of the North West slopes and plains of New South Wales received between 50 and 98 mm of rain during this event and localised flooding of rivers and streams occurred.

During the 26/12/2020, there were thunderstorms on the ranges and the Hunter Valley of New South Wales although no such chase could be undertaken as my wife and I were in Albury on the New South Wales Victorian State border.

It is interesting to see that west of Conroys Gap (West of Yass New South Wales), the impacts of the La Nina weather pattern is significantly less. The region further west is typically dry with the grass having dried out. Near Albury, it is significantly dry and the fire risk is heightened. Where we are staying, it has been quite hot and it reached 35.6C on the 27/12/2020. Further west, it has been hotter.

Near Robinvale in North West Victoria, a bushfire was burning out of control by evening on the 27/12/2020 due to high winds and high temperatures. It reached 40C at Mildura and the high 30s across south west New South Wales on the 27/12/2020 being the areas not impacted by the recent rain events.

During the evening of the 27/12/2020, a strong cool change passed through southern New New South that brought little if any rain but brief wind gusts of 52 km/h at Albury Airport. The cool change brought little rain across northern Victoria but its impact in eastern New South Wales will be different to that of northern Victoria due to more moisture being available.

The attached rainfall plot produced on the Bureau of Meteorology "Water and the Land" website prepared on the 24/12/2020 is showing the weekly accumulative rainfall for the Murray Darling Basin. As shown, the heaviest falls have occurred across the north east of New South Wales. There is a narrow corridor focused on northern Victoria and south west New South Wales that has missed most of the recent rainfall events. This is the region that has been experiencing the high summer temperatures and where the bushfire threat is most high.

Rain, storms, heat and wind - NSW - A state of contrasts - 22 to 28 December 2020

The second plot is showing the location of the rain event to 9 am 22/12/2020 across the north west New South Wales.

Rain, storms, heat and wind - NSW - A state of contrasts - 22 to 28 December 2020

Heavy rain, Floods, Storms and wind – NSW, QLD and NE Victoria – December 14 to December 19 2020

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Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020

A significant weather event has impacted eastern Australia between December 14 and December 19 2020 with the area stretching from South East Queensland, Eastern New South Wales and into North East Victoria being most affected.

In particular, flooding rains has impacted north east New South Wales around the Bellinger Valley, Coffs Harbour Region, Grafton, the Tweed River Valley and South East Queensland while thunderstorms have impacted much of eastern New South Wales which has included localised heavy falls, damaging winds and hail. As usual, thunderstorms are often hit and miss and rainfall totals have varied considerably.

Damage along the coast has been significant which has included beaches being washed away or covered in foam, property damage and roads being washed away. There was also a landslide on the Dorrigo Road between Dorrigo and Bellingen.

At the present time, the cost of the weather events are being tallied.

As shown in the attached plots prepared on the Bureau of Meteorology "Water and the Land" sites, the heaviest falls have been around the Tweed River Valleys and the Bellinger Valley including the Coffs Harbour Region.

Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020
Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020

On the 14/12/2020, significant rainfalls impacted the Sunshine coast and its hinterland with many locales receiving more than 100 mm of rain.

Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020

At the local level, some of the rainfall totals have been significant. A weather station at Upper Springbrook (Queensland) recorded 952 mm of rain during this event which exceeds the average annual rainfall for cities such as Melbourne, Perth, Canberra and Adelaide.

Some rainfall totals include:-

1 - Grafton - 13/12/2020 - 79.6 mm, 15/12/2020 - 125.2 mm and the 17/12/2020 - 99 mm. As at 20/12/2020, 477.6 mm of rain has fallen at Grafton which is far in excess of the average December average of 91.4 mm.

2 - At Coffs Harbour Airport, 12/12/2020 - 150.6 mm, 15/12/2020 - 73.8 mm and the 16/12/2020 - 116.2 mm of rain fell.

3 - At Dorrigo which is close to the wettest location in New South Wales, 435 mm of rain has fallen between December 1 and December 20 2020. This takes the yearly rainfall to date to 2,344 mm which is well in excess of the average to December of 2,013.5 mm.

4 - At Bellingen in the Bellinger Valley, a rain gauge recorded 220 mm of rain during one these events. The topography of the Bellinger Valley often enhances the rainfall.

5 - On December 17 2020 at Lismore (NSW), 202.8 mm of rain fell which resulted in riverine flooding and evacuations. As at December 20, 2020, Lismore has received 484.2 mm of rain which is well in excess of the usual December average of 121.9 mm.

This is showing the scale of the event. While the heavy rain and flooding is generally limited to north east New South Wales and south east Queensland, thunderstorms have impacted large areas of inland New South Wales including the Sydney region which has delivered localised but significant rainfall totals. Samples include:-

1 - Albury (NSW / Victorian state border) - A single thunderstorm event between 11 pm and 3 am on the 16/17 December 2020 dropped 50.2 mm of rain including 18 mm during the period 1.05 am and 1.30 am. The same storm system produced 42 mm of rain at nearby Barnwartha to the west.

2 - Dubbo - Storms dropped 26.8 mm of rain on the 17/12/2020.

3 - Gunnedah (North west slopes and plans of New South Wales) 17 - 18 December 2020 - Storms delivered rainfall totals of 36.2 mm and 41 mm and peak wind gusts of 98 km/h. Those gusts occurred during a brief period between 4.20 pm and 4.28 pm on the 18/12/2020.

One such storm on Thursday afternoon 17/12/2020 impacted parts of Western Sydney as shown in the attached photo. This storm was slow moving and approached Blacktown from the south although at sunset, the storm cell went into sharp decline. During its most active phase, the storm was producing strong updraft towers, numerous cloud to ground lightning strikes and an interesting rain free base. There was little evidence of the storm cell after sunset due to its rapid decline.

Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020
Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020
Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020
Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020

On Friday afternoon, a short sharp rain shower developed over Western Sydney although no lightning was observed from this cell. A rainbow was later photographed.

Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020

The photos attached to this post of the Thursday afternoon storm were taken from a park looking south from Blacktown.

Heavy rain, Floods, Storms and wind - NSW, QLD and NE Victoria - December 14 to December 19 2020

Heavy rain event and floods NW Sydney 9 and 10 February 2020

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Heavy rain event and floods NW Sydney 9 and 10 February 2020

Following a four month period between October 2019 and February 2020 in which heatwaves drought and bushfires gripped much of Eastern Australia, a change in the weather pattern saw just how variable our weather can be.

The last of the extreme heat for the summer 2019/2020 occurred on February 1 2020 in which the maximum temperature soared to 46.1C in Blacktown (Western Sydney) and other nearby locales. Following this, a cool change swept through south eastern Australia and a few days later, a significant rain event took hold culminating in flooding rains of the 9 and 10 February 2020.

Heavy rain event and floods NW Sydney 9 and 10 February 2020

This was an important event because much of the fire activity that was still occurring to the west and south west of Sydney ended.

Heavy rain event and floods NW Sydney 9 and 10 February 2020

On the 9 and 10 February 2020 Sydney received a significant soaking of rain that culminated in flooding of low lying areas which was a stark contrast of what was occurring during the previous weeks. The weather had swung suddenly from drought and heatwave to flooding rains.

Heavy rain event and floods NW Sydney 9 and 10 February 2020

During the afternoon of the 10/2/2020, my wife and I undertook a drive into outer north west Sydney to take a look at what was occurring. The images provided in this post taken by my wife Katya and I are showing some of the flooding impacts across low lying areas especially near Windsor and Pittown.

During this 2 day period, Western Sydney experienced some of the heaviest rain that I had personally seen in the 22 years of living here and it was the most rain that I had personally experienced in one day. In particular, some of the rainfall totals for 24 hours to 9 am 9/2/2020 include:

Prospect Reservoir - 104 mm.

Auburn / Lidcombe / Berala - 73 to 79 mm.

Bankstown - 79 mm followed by Blacktown on 78 mm.

On the 10/2/2020, the rainfall totals peaked and for the 24 hours to 9 am 10/2/2020, some of the following totals were observed across Sydney.

Campbelltown (Northern areas - up to 245 mm).

Chatswood area - Up to 240 mm.

Sydney airport and nearby suburbs - 163 mm to 194 mm.

Hornsby - 188 mm.

Sydney City (Observatory Hill) - 176 mm.

Blacktown - 144 mm (Total for the 2 days where we lived reached 222 mm).

Heavy rain event and floods NW Sydney 9 and 10 February 2020
Heavy rain event and floods NW Sydney 9 and 10 February 2020
Heavy rain event and floods NW Sydney 9 and 10 February 2020

One benefit of this is that all fire activity ceased and it marked the beginning where recovery could commence. While this event created new issues such as flooding and flood related evacuations, it was certainly a rain event that was much needed. Following this event, February 2020 turned out much cooler when compared to the previous 4 months.

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