Rain and storms December 29 and 30 2020 while dry in SW New South Wales.

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Rain and storms December 29 and 30 2020 while dry in SW New South Wales.

Similar to the previous post, rain continues to drench parts of eastern New South Wales while the south and west of the state remains dry resulting in wide variations of weather.

For the 24 hour period to 9 am 30/12/2020, Mona Vale in north east Sydney was drenched with 105 mm with falls of 73 to 78 mm falling in nearby suburbs.

Constant rain has also featured across other parts of New South Wales and cumulative totals are mounting.

For the period 1 December to the 30 December 2020, Horsley Park in Sydney's west has received 112 mm of rain against an average of 69.9 mm while Penrith has received 117 mm against an average of 65 mm. Furthermore, Sydney City has received 118 mm against an average of 77.1 mm.

Afternoon thunderstorms featured across Sydney and areas further north on the Monday 28 December 2020 although we were in Albury.

Interestingly, following the passage of the cold front in southern New South Wales , large banks of alto cumulus castellatus clouds dominated the sky for much of the morning although this cleared during the afternoon.

During the drive from Albury to Sydney on the 29/12/2020, we left Albury under clear skies. At Wagga Wagga, it was clear and sunny. At Gundagai, small cumulus clouds were observed. Between Gundagai and Yass, more and more clouds were observed and by the time we reached Goulburn, it was cool and cloudy with occasional drizzle patches. We reached Sydney under showery skies.

There has been a distinct dry line between the wetter eastern half and the drier western half centred close to Conroys Gap. Conroys Gap is a pass that rises approximately 650 metres in height being part of a wider north to south range of hills that divides the southern tablelands with the slopes and plains just to the west of Yass. This is where the boundary between the two air masses has been situated over the past few days.

In this instance, the eastern half has seen much of the rain while the south and west has missed the event.

Weather models are now showing and suggesting that some of the rain and storms should start to penetrate further inland thus reaching some of the drier western and southern areas during the period 31 December 2020 to the 6 January 2021. Rainfall models do suggest falls of 25 mm to 50 mm for the drier regions with continued rain for the eastern half of the state.

The attached photo taken just east of Albury (27/12/2020 looking west) is showing the typical weather conditions being experienced in southern New South Wales ahead of the most recent cool change being thin high cloud as temperatures soared close to 36C. However with elevated fire danger, fires have been a concern. The plume of smoke from a grass or bushfire is visible on the distant hills. With forecast rain over coming days, the elevated fire danger should be reduced.

Rain and storms December 29 and 30 2020 while dry in SW New South Wales.

The attached model from the Bureau of Meteorology "Water and the Land" site prepared on the 30/12/2020 is showing forecast rainfall up to the 6/1/2021. It is showing that most of New South Wales including the drier areas should benefit from the developing weather system.

Rain and storms December 29 and 30 2020 while dry in SW New South Wales.

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

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