Tropical Cyclone Shaheen Oman – 2 to 4 October 2021

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A highly unusual tropical cyclone has formed in a location that is highly unexpected at this time of year off the coast of Pakistan. This storm is highly unusual for the following reasons:-

1 - It has formed off the coast and south of Pakistan.
2 - It is tracking west towards Oman and even threatening the city of Muscat.
3 - It has formed over waters heated to 29C but as it moves west, it will move over even warmer waters heated to around 31 to 32C.

A close up view of this system appears to show a very small eye ringed by thunderstorms. It is rare to see such storms in this part of the world but a closer view of the CIMSS models is suggesting further strengthening prior to landfall. The storm has reached category 1 on the Saffir Simpson Scale with peak wind of 75 to 75 knots at the core (120 km/h to 138 km/h) but a forecast model suggests that the storm could sustain peak wind gusts to 80 knots (148 km/h) at or just prior to landfall.

This storm would start to approach a Category 2 system at such intensity.

This part of the world has a semi arid to arid climate and such storms are rare but not unheard of.

A population density plot has been overlaid across the satellite photo using NASA Worldview which shows that other than the city of Muscat, the region is not heavily populated. Should the storm make landfall as suggested over Oman near Muscat, it would bring heavy coastal rainfall but the storm would decay fast.

Severe Storms Western Sydney 1st October 2021

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Severe Storms Western Sydney 1st October 2021

More instability across eastern NSW with severe storms developing about midday over the Blue Mountains and SW of Sydney. for several hours the storms developed west of Warragamba and moved southeast. Gradually outflow began to force the boundary slowly east. The development of storms also progressed towards Penrith and finally moved across the Sydney basin. Initially, the air was dry across the metropolitan area feeding into the storms meaning bases were slightly higher although consolidated. As the outflow boundary relocated eastwards, moisture did feed into the new storms.

The first cell SW of Glenmore Park did develop reasonable base structure though it lacked instability - the wind shear pushing over. This cell followed by another moved southeast. As the boundary consolidated over the lower Blue Mountains, cells became more organised but outflow dominant. The third more significant cell produced hail over Glenmore Park. The outflow though eventually pushed the activity near Blacktown which eventually pushed towards the coast.

 

Severe Storm Impacts Western Sydney – Friday 1 October 2021

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During the period 3.30 pm to 6 pm, a large thunderstorm impacted much of Western Sydney which travelled south east across the city before passing out to sea.

As shown in the attached photos, this storm developed over Western Sydney. As it tracked towards Blacktown, this storm appeared to develop a new base which became a significant feature. My images shows the base in detail including a green tinge at times.

As the base passed over, the warm winds of the day were suddenly replaced with cold gale force winds from the south east. This was followed by a period of moderate to significant rain. Although further east and south, hail is likely to have fallen given what was occurring.

This was a much stronger thunderstorm than that of Thursday evening and included some significant cloud to ground lightning strikes. The heaviest rainfall from the event included:-

1 - Blacktown Dog Pound - 24 mm which appears to be the heaviest rainfall.
2 - Sydney Airport weather station recorded 22.8 mm from the event including 13.6 mm between 5.23 pm and 5.30 pm which is just under 2 mm a minute for seven minutes. A peak wind gust of 61 km/h was also recorded during the same period.
3 - Holsworthy recorded 22 mm between 4.30 pm and 6 pm during the event.
4 - Horsley Park recorded 12.8 mm between 4.30 pm and 5 pm.

This was an intense storm and a severe thunderstorm warning was issued for this event for large hail, gale force winds and heavy rain covering areas such as Liverpool, Fairfield and Parramatta.

An earlier thunderstorm passed over the Campbelltown region that dropped up to 47 mm at Holsworthy Training Area and 37 mm at nearby Kentlyn.

The images attached to the post are taken at Doonside between 4.10 pm and 4.40 pm. The radar image (2 frames) are also attached which shows the storms peak intensity at or just east of Blacktown.

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