During Saturday and Sunday, the passage of a strong cold front across southern Australia will mark the end of the summer season weather conditions and herald in the beginning of more autumn like weather conditions. This change marks the change of seasons for southern Australia.
Ahead of this change, weather conditions will become hot at least briefly.
To show the contrasts of conditions, Saturday is expected to be relatively warm to hot across much of eastern Australia and forecast maximum temperatures include:-
Sydney - 30C to 34C.
Canberra - 29C.
Ivanhoe - 38C
Hay - 37C.8C.
Albury - 33C.
Batemans Bay - 31C.
The air is relatively cool to cold behind this change with forecast maximum temperatures in the low 20s and even dropping to under 10C across higher elevations of New South Wales and Victoria. While the air is not cold enough for snow, it will feel more like autumn.
A significant rain event is expected with this change across eastern New South Wales with forecast models showing 20 to 50 mm of rain expected following the passage of the cold front.
The attached temperature plots from the BSCH for Saturday and Sunday afternoons shows a stark contrast of maximum temperatures across the two days with Sunday being the opposite of Saturday.
The satellite cloud picture of Australia (Himawari) of Saturday morning is showing the cloud mass that marks this change. The change will pass across Victoria during Saturday and should arrive in Sydney Sunday morning. This event will also herald in the beginning of the next rain event for Sydney.
The period between the 8 and 12 of March 2021 has been active and rain / showers and storms have been a feature across large areas of eastern New South Wales. Storms have impacted Sydney on at least 2 days during this period being Monday afternoon with the area between Penrith and Blacktown being impacted the most and Friday afternoon with southern Sydney being impacted.
Rain and storms have featured across wide areas and some of the more significant events include:-
8 March 2021
Penrith to Blacktown Storm event - While the storm was embedded within existing cloud, this storm that traversed the Penrith to Blacktown region produced the occasional cloud to ground lightning including two cloud to ground strikes that occurred well ahead of the main storm core.
This storm produced peak wind gusts of 78 km/h at Penrith and a peak rainfall intensity of 13.4 mm between 4.25 pm and 4.30 pm (An intensity that exceeded 2 mm per minute). This storm impacted Blacktown and produced strong to gale force winds (Downbursts) and short but sharp heavy bursts of rain. Erskine Park recorded 23 mm followed by Penrith where 18.2 mm. The area around Blacktown had between 12 and 16 mm of rain.
The photos attached to this post are taken as the storm was approaching from the west.
This storm went into rapid decline as it passed over the Parramatta area.
Taree - A significant thunderstorm impacted the town which resulted heavy rainfall of up to 45 mm to 5.35 pm. At 5.01 pm, the rain gauge had registered 7.2 mm. However, by 5.10 pm, the rain gauge had recorded 29.2 mm. This is a fall of 22 mm in 9 minutes or just over 2 mm per minute.
The local weather station recorded peak wind gusts of 78 km/h during the peak of the storm.
11 March 2021
Cowra - The town was impacted by a significant event which resulted in 48 mm falling with 29.2 mm falling in 1 hour between 3.30 pm and 4.30 pm.
Goulburn (Gundowringa) (NW of Goulburn) - A rain / storm event saw a fall of 64 mm at this location.
Wingen - For the 24 hours to 9 am, 62 mm of rain fell.
Oberon - For the 24 hours to 9 am, 58 mm of rain fell.
Orange - For the 24 hours to 9 am, 52 mm of rain fell.
Other significant falls include Ben Bullen 55 mm and Newbridge 53 mm.
Southern Sydney - At least two storm cells have impacted the coastal suburbs close to the airport and Cronulla which has seen rainfall totals top 45 mm at Little Bay and 42 mm at Marrickville Golf Club.
Sydney’s Observatory Hill recorded 20 mm of rain between 7.30 pm and 8.10 pm with a total of 25.6 mm falling.
Wallis Lakes (Pacific Palms) on the lower North Coast recorded 104 mm of rain.
The last photo attached to this post is showing one of the storm cells just after sunset looking east.
There have been other similar events across the Hunter Valley, North Coast, North West Slopes and Central Tablelands during this period. Generally only the far west and south west of New South Wales have missed out on this event.
Tropical Cyclone Niran has defied the initial forecasts of Monday and has become a much stronger storm than initially expected. Instead of reaching a peak maximum intensity as a Category 2 storm on the Saffir Simpson Scale, this storm progressed into a Category 3 system as it crossed the Coral Sea away from the Queensland Coast.
This storm then developed further to a Category 5 storm across open waters but has weakened slightly to a Category 4 storm on the Saffir Simpson Scale. The tropical cyclone is currently sustaining wind gusts of 130 knots (Approximately 241 km/h) at the core and is moving fast at approximately 37 km/h towards the south east and towards New Caledonia.
The island of New Caledonia is currently under significant threat, especially for the area along the south west coast due to its proximity to the island but may pass just to the south and south west of the island. The south west coastline is expected to come under significant threat of gale force winds and heavy rain over coming hours.
Once the storm clears the coastline, it is expected that the storm will decline in intensity and weaken to a depression by Sunday and Monday.
The Worldview images show a small compact tropical cyclone with visible convection (Cumulonimbus clouds) and a very small eye of approximately 20 km in diameter. To date this season, this is by far the strongest storm to develop within Australian waters.
The images are taken from Worldview (NASA) dated 5/3/2021, Himawari and CIMSS generally at the time the storm is within its strongest phase.