Heavy rain and flooding NE NSW and SE Qld 11 to 14 December 2020

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Heavy rain and flooding NE NSW and SE Qld 11 to 14 December 2020

A significant rain event rain across the coastal regions of north east New South Wales and South east Queensland has been unfolding and the event is likely to continue for the next few days.

The event has been coastal in nature with the rain reaching the eastern side of the Great Dividing Range but not penetrating westwards into the inland areas. As at Sunday morning 13/12/2020, very little rain has penetrated inland and during the same time, very little rain has moved southwards of the Mid North Coast.

Heavy rain and flooding NE NSW and SE Qld 11 to 14 December 2020

In Particular and for the 24 hours to 9 am 12/12/2020, the heaviest rainfall occurred around Coffs Harbour and the nearby Bellinger Valley. It is likely that the surrounding hills intensified the rainfall due to orographic processes with the heaviest rainfall being concentrated to localities within the valley but east of Point Lookout.

Heavy rain and flooding NE NSW and SE Qld 11 to 14 December 2020

The heaviest rain includes 203 mm at Bowraville and 161 mm at Bellinger. Coffs Harbours was drenched with rainfall reaching 150 mm up to 156 mm.

Another location on the mid north coast being Logans Crossing received 187 mm.

For the 24 hours to 9 am 13/12/2020, some exceptional rainfall totals have occurred within the Tweed River Valley areas and south east Queensland including the Gold Coast city area.

For New South Wales, the heaviest rainfall includes - Tweeds Heads - 253 mm, Bray Park - 250 mm, Uki - 211 mm and Repentance - 182 mm. Most localities within the Tweed River Valley has been drenched with flooding likely.

Heavy rain and flooding NE NSW and SE Qld 11 to 14 December 2020

In south East Queensland, some exceptional rainfall totals for the same period includes Upper Springbrook Alert - 475 mm, Tomewin Alert - 370 mm and Tallebudgera - 346 mm. Such totals and others are confined to areas just south of Brisbane encompassing all the Gold Coast City areas and its hinterland.

Heavy rain and flooding NE NSW and SE Qld 11 to 14 December 2020

The forecast models continues to suggest further heavy rain which has potential to cause further flooding. Some of this rainfall is expected to drift further south towards Sydney later in the week although such high totals are not expected. While some models suggest that some moderate rainfall will make its way into the eastern inland New South Wales, other models are suggesting that only light falls are likely to occur with the heaviest falls being concentrated to coastal areas north of Sydney.

Tuesday afternoon storms with small hail 1/12/2020

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Tuesday afternoon storms with small hail 1/12/2020

The weather across Sydney 1/12/2020 turned out to be a day of remarkable contrasts. A cloudy morning was following by a long period of heating and sunshine which was then followed by a dramatic late afternoon / evening thunderstorm that produced small hail.

The maximum daytime temperatures occurred late in the day as a result of what occurred. It reached a maximum of 38.5C in Penrith, followed by 38.1C at Richmond, 35C at Blacktown and Horsley Park and 33.6C at Parramatta. It was cooler further east.

Late afternoon, a thunderstorm crossed over much of Sydney and while rainfall totals were not significant (Between 7 and 14 mm of rain), it had a dramatic impact.

Tuesday afternoon storms with small hail 1/12/2020
Tuesday afternoon storms with small hail 1/12/2020

The storm event produced maximum peak wind gusts of 106 km/h at Richmond which was enough to bring down trees. Peak wind gusts reached 83 km/h at Penrith between 6.38 pm and 6.47 pm. In addition, lightning strikes caused some power outages and one bell tower attached to a house in Ashfield appears to have been struck by lightning which caused a fire but it was contained to the bell tower structure.

Tuesday afternoon storms with small hail 1/12/2020
Tuesday afternoon storms with small hail 1/12/2020

Over Blacktown, a small storm cell formed ahead of the main line of storms which produced small hail in the range of 0.5 mm to 0.9 mm in diameter. My wife and I were able to collect these using a plate before they melted. This storm cell also produced a sharp but brief downburst accompanied with a short heavy burst of rain. This storm cell eventually merged with other storms as the system passed across Sydney. The main line of storms followed shortly afterwards which produced rain and some wind.

Tuesday afternoon storms with small hail 1/12/2020

Photos of the event are showing developing storms ahead of the main line followed by an interesting storm base. Much of the lightning was within cloud although there were the occasional cloud to ground strikes. The storms were fast moving and all activity had cleared by sunset.

Tuesday afternoon storms with small hail 1/12/2020
Tuesday afternoon storms with small hail 1/12/2020

Heat continues for NSW Sunday 29 November 2020

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Heat continues for NSW Sunday 29 November 2020

Sunday the 29/11/2020 has followed on from Saturday in which the dome of heat continues to impact much of New South Wales, especially for areas in a line stretching from Moruya on the New South Wales south coast to Broken Hill in far Western New South Wales and all areas towards the north.

Following on from Saturday which saw maximum daytime temperatures peak at over 40C for much of Sydney (Such as 40.5C at Blacktown), Sunday the 29/11/2020 has become a carbon copy of Saturday. This is an exceptionally rare event for Sydney especially in November.

Overnight minimum temperatures dropped to 25.9C at 1 am at Penrith which increased to 29.9C by 3 am and 31.8C by 6 am and 33.7C by 9 am. At the time of writing this post, the temperature has already reached 40C at Penrith.

At Blacktown, the minimum temperature of 27.9C was observed at 3.30 am which had increased to 30.5C at 6.30 am and 33C at 9 am. Again, the temperature depending on location is currently around 39C to 40C.

Interestingly, it was difficult to sleep at night and my wife and I went outside at around 3 am only to discover that it was cloudy with a very light shower of rain falling although not enough to cause much dampness to the ground.

At Observatory Hill, it is suggested that the minimum overnight temperature of 25.3C is the hottest November night since 1967. Although records are being checked, I have found a record of a warm 24.8C on the night of the 14/11/1967 which maybe the record that is being referred to.

At the time of writing at 2 pm, Penrith has reached 40C, Observatory Hill has reached 40.5C, Sydney Airport 42.6C and Sydney Olympic Park has reached 41.6C. This is reinforced with low due points of 8C to 12C varying across Sydney and wind gusts reaching 82 km/h at Sydney Airport with strong winds from the north west.

As shown in the attached photo, clear skies predominate with thin high cirrus cloud.

Heat continues for NSW Sunday 29 November 2020

The plots from the Bureau of Meteorology "Water and the Land" for the 29/11/2020 is showing the impact of the heat dome across New South Wales for Saturday including the maximum temperature anomaly. These are showing how significant this event is with large areas showing a maximum temperature anomaly of at least 12C above the long term average.

Heat continues for NSW Sunday 29 November 2020
Heat continues for NSW Sunday 29 November 2020
Heat continues for NSW Sunday 29 November 2020

For Sydney, the heat will end once the cooler change passes through late on Sunday.

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