Monthly Archives: May 2021

A succession of cold nights – May 15 to 21 2021 – NSW

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Following a succession of cold fronts across southern Australia, large areas of Victoria and New South Wales has recently experienced a succession of unusually cold nights for May. It appears that winter has arrived earlier than normal for 2021 as some of the minimum temperatures experienced are more likely to occur during June, July and into August than May.

The NASA Worldview image of Sunday May 16 2021 attached is showing extensive snow existing across the Snowy Mountains region of New South Wales. Similar snowfalls have also occurred across the higher regions of North East Victoria as a result of the recent cold fronts.

Frosts have been common and mornings have been cold. Minimum night time temperatures have also been colder than normal across Western Sydney.

A review of several weather stations across the state of New South Wales has identified the following minimum night time temperatures which have occurred between the 15 and the 21 May 2021.

1 - Albury Airport - 16 May 2021 - Minus 1.0C.

2 - Armidale - Overnight minimums have fallen between minus 0.7C and minus 5C between the 15 and the 21 May with the coldest minimum being minus 5 on the 16/5/2021. Armidale is elevated at 980 metres above sea level and much of the town sits within a valley where cold air pools at night and hence it can be colder in town than on the summit of nearby surrounding hills.

3 - Bathurst - The coldest morning occurred on the 19/5/21 where minus 4.5C occurred. It also fell to minus 4.1C on the morning of the 16/5 and minus 4C on the morning of the 18/5.

4 - Braidwood - 16 and 19 May 2021 - Minus 3.7C occurred.

5 - Cabramurra - 16 May 2021 - Minus 4.1C occurred.

6 - Cooma Airport - 18 May 2021 - Minus 6.4C occurred, 19 May - Minus 5.9C occurred and 20 May - Minus 5.3C occurred.

7 - Dubbo - 16 May 2021 - Minus 2.5C occurred.

8 - Glenn Innes Airport - 17 May 2021 - Minus 7.5C occurred.

9 - Goulburn - 19 May 2021 - Minus 5.1C occurred.

10 - Lithgow - 16 May 2021 - Minus 4.2C occurred.

11 - Oberon - 17 and 19 May 2021 - Minus 3.6C occurred.

12 - Orange - 16 May 2021 - Minus 4.0 occurred.

13 - Perisha Valley - 16 May 2021 - Minus 9.4C occurred.

14 - Tenterfield 17 May 2021 - Minus 5.2C occurred.

The coldest minimums have occurred at towns that are elevated but within valleys including Armidale, Bathurst and Lithgow.

Even in Western Sydney very light early morning front has been observed in the western areas of Blacktown around Doonside.

The plots attached to this post are taken from the Bureau of Meteorology Water and the Land and each show the minimum temperatures and temperature anomalies that have occurred during the period.

North Indian Ocean – Tropical Cyclone Tauktae – 15 to 18 May 2021

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A look at the Worlds tropical cyclone tracks will reveal that the majority of all tropical storms form within certain ocean areas including the north west Pacific Ocean, an area of the west coast of Central America and Mexico, the tropical Atlantic Ocean north of the Equator including the Gulf of Mexico, the Western Pacific Ocean including areas within Australian waters and the tropical Indian Ocean within the southern hemisphere between Australia and Africa.

There is also another area where such storms can occur but are much less likely being the North Indian Ocean situated between India and the Arabian Peninsula. Occasionally a storm will form within this area and track towards the North West India / Southern coast of Pakistan but instances of such occurrence are relatively rare.

During the period 15 to the 18 May 2021 a significant tropical storm has formed within an area where tropical cyclones are generally rare. This storm was named Tropical Cyclone Tauktae which formed off the west coast of India then tracked northwards towards the north west coast of India and even threatened the south east coast of Pakistan. Landfall occurred between Porbandar and Mahuva (Gujarat State - India).

At peak intensity, this storm reached Category 4 on the Saffir Simpson Scale with peak wind gusts at the core of at least 115 knots (Approximately 213 km/h). This storm was supported by ocean waters within the range of 30 to 31C and atmospheric conditions were certainly favourable for supporting such a strong storm. Strong convection and thunderstorm cells were visible on satellite images especially to the south of the eye which supported the storm. This storm weakened just before commencing landfall over Gujarat State.

This storm has brought heavy rain especially around Saurashtra and numerous west coast localities were warned for heavy rain as the storm tracked northwards. Media reports suggests a significant impact onto the north west Indian coast with at least 26 fatalities mainly within coastal locations, flooding, heavy rain and intense wind gusts. It is believed that upwards of 200,000 residents were evacuated prior to the storm making landfall.

The images attached to this post are taken from Worldview and CIMSS. Information was also sought from the India Meteorological Department 17/5/2021 prior to the storm making landfall.

Heavy rain and flooding – New South Wales South Coast – 4 to 7 May 2021

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Following an exceptionally wet March and a subsequent dry April 2021, the first week of May 2021 across the east coast of Australia has again been wet.

The initial Bureau of Meteorology rain models suggested that upwards of 50 mm of rain would fall across much of the east coast especially along the coastal strip of New South Wales south of Sydney. Models suggested slightly heavier falls of between 50 mm and 100 mm could fall in isolated locations. The event would not have been considered significant for the 4 day period.

However, rainfall totals in some locations south of Sydney especially within the Shoalhaven region, an area between Ulludulla and Batemans Bay and around Bega not only exceeded expectations but have been heavy leading to isolated flooding events.

Accumulative totals have reached between 200 mm and 300 mm for the event and even across Sydney rainfall totals exceeded expectations. As a result, moderate flooding has occurred at Menangle Bridge on the Nepean River south west of Sydney and minor flooding has occurred along the Shoalhaven River at Nowra.

Some of the daily rainfall totals have been considerable during this event although falls over 100 mm have been concentrated within small localities.

For the 24 hours to 9 am 5/5/2021, the heaviest rainfall totals include:-

Black Range (Near Bega) 156 mm.

Bega River at Kanoona 123 mm.

Bega - 122 mm.

Lake Tabourie - 100 mm.

Angledale - 119 mm.

All localities except Lake Tabourie are close to Bega on the New South Wales South Coast.

For the 24 hours to 9 am 6/5/2021 some rainfall totals include:-

Brogers No 2 (Brogers Creek) - 129 mm.

Fitzroy Falls Dam - 114 mm.

Nowra ASW - 113 mm.

Brooman (Directly north of Batemans Bay) - 104 mm.

Such falls were limited to small areas. Here in Sydney rainfall totals ranged from 8.2 mm at Penrith to 40 mm at Lucas Heights for the 24 hours to 9 am 6/5/2021. There were short bursts of heavy showers throughout the day but for the most part, most rainfall totals across much of Sydney fell between 20 mm and 26 mm.

For the 24 hours to 9 am 7/5/2021, even heavier rainfall totals occurred within small areas south west of Wollongong encompassing the Kangaroo Valley, parts of the Shoalhaven region and the eastern side of the Southern Highlands around Fitzroy Falls and Robertson. The heaviest totals include:-

Brogers No 2 (Brogers Creek) - 182 mm.

Fitroy Falls Dam - 171 mm.

Beaumont (The Cedars) - 162 mm.

East Kangaloon - 156 mm.

Robertson - 147 mm.

It is clear that Brogers No 2 (Brogers Creek) has had more than 300 mm during this rain event.

The weekly rainfall plot for New South Wales to May 7 2021 on the Water and the Land site clearly shows that large parts of the New South Wales South Coast has recorded between 200 mm and 300 mm of rain including an area south west of Wollongong, an area between Ulludulla and Batemans Bay and another small area close to Bega.

This event has impacted the Warragamba Dam catchment and it is likely that more water inflows will result in water spilling again over the dam wall.

Conditions are now clearing and further significant rainfall is not likely from this system. This will allow flood waters that have occurred to subside.

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