Tropical Depression 16 “A threat of a major typhoon” August 14 2021

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The north - west Pacific Ocean has to this time this season been relatively benign in terms of intense storms and typhoons.

There have been tropical depressions / tropical storms and a small number of weak typhoons (No stronger than Category 1 systems) but none of these have been major events. A few have made landfall producing heavy rain and flooding in affected regions such as what has occurred recently in coastal China near Shanghai but generally none have reached the higher categories on the Saffir Simpson Scale.

There is now a threat in the form of “Tropical Depression 16”. The storm is currently not named but a pack of thunderstorms in the western Pacific Ocean east of the Philippines is beginning to rotate around a small low pressure cell and gathering strength.

A close up view of the system from satellite imagery is clearly showing convection and cumulonimbus cloud towers and intense storms surrounding the low pressure cell.

This storm will approach the Philippines and Taiwan waters in coming days and strengthen into a typhoon. The storm appears to be different to many others that have formed and died in recent weeks across the north west Pacific Ocean.

The storm is about to track over oceanic waters that have been heated to 30C or more and conditions are favourable to support a significant storm / typhoon given location. This is one storm to watch given its shape and dynamics.

IN particular, CIMSS is forecasting the development of a typhoon in coming days at least to Category 1 status within 5 days with wind gusts to 70 knots (130 km/h) at the centre although forecasts do not currently exceed 5 days. Within this time, the storm will become a threat to the north east coast of the Philippines and or Taiwan depending on its future track.

This storm has potential to be the strongest storm so far this season and will be watched in coming days to see what occurs.

Typhoon In-Fa – NW Pacific Ocean – Taiwan and China.

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A sluggish and slow moving typhoon is currently slowly moving towards the city of Shanghai however landfall is expected to the south of the city. The storm has struggled to maintain any significant strength throughout its life span but it has changed course over recent days. While it has reached a Category 2 system on the Saffir Simpson scale, it has weakened somewhat to a Category 1 System with peak wind gusts ranging between 65 and 70 knots (Between 120 and 130 km/h) at the core.

It is not a strong storm in terms of wind intensities but given its speed, it does have potential to unleash significant rainfall and flooding once it approaches land. This storm is expected to weaken further to a tropical depression at landfall below the threshold of a typhoon.

China has recently experienced two major flood events with one such event along the southern coast near Yangjiang (Southern Guandong Provence) caused by a weak typhoon named Cempaka and another such event in Zhengzhou in China’s central Henan province.

Both events have caused significant losses and flooding including fatalities. The latest storm has the potential to add to the flooding events that have already occurred.

Typhoon In - Fa presently has a well defined eye and is passing over waters of approximately 28 to 29C but will encounter a slightly more unfavourable environment just prior to landfall.

The main impact would be flooding at landfall. A population density plot for Eastern China has been generated using NASA Worldview. Given the forecast track shown on CIMSS, it does show that this storm has potential to unleash a significant flood event for eastern China close to Shanghai.

This is a highly populated region of China and as such, this storm has potential to be another significant event and the third such event for China in recent weeks.

Prolonged outbreak of rain, cold, storms, wind and snow Southern Australia 13 to 18 July 2021

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During a five day period between the 13 and the 18 July 2021, a significant low pressure system has been passing to the south of the Australian continent which has resulted in a number of cold fronts passing across South Australia, Victoria, New South Wales and Tasmania.

Each frontal system has provided a continued outbreak of cold wintry weather across the south and rainfall figures are starting to accumulate. Low level snow is occurring across the southern ranges and into the Central Tablelands.

On Thursday evening, one particular front generated thunderstorm activity across the south west part of New South Wales and one strong cell passed over rural areas west of Wagga Wagga. Additionally, two separate storm cells passed along the New South Wales / Victorian state border. The cells brought a high frequency of lightning strikes and the Albury Airport recorded 8.8 mm of rain in 21 minutes and a total of 20 mm from the event.

Winter thunderstorms are rare in this part of the state but having storms occur after sunset in mid July makes this event even more unusual.

Rainfall accumulations across the five days are beginning to mount although the heaviest falls are relatively localized to the areas immediately to the west of the Snowy Mountains and the mountainous areas of North East Victoria. Accumulations have now reached in excess of 100 mm within isolated areas.

Interestingly, stark rain shadows lie to the east. Air is rising across the ranges and the rainfall is being dropped within the highly exposed locations but areas to the east of the Great Dividing Range have remained relatively dry. Thus, the same locations have been receiving rainfall across the 5 days.

Some notable weather events identified are:-

WIND

Roseworthy - (South Australia). The weather station recorded peak wind gusts to 95 km/h between 3.34 pm and 3.42 pm on the 15/7/2021 as one particular front passed through.

Albion Park - (Wollongong New South Wales). The weather station recorded peak wind gusts of 95 km/h between 12.30 pm and 12.35 pm 16/7/2021 as a front passed through.

Moss Vale - (New South Wales Southern Highlands). A peak wind gust of 85 km/h occurred at 12.07 pm 16/7/2021 as a cold front passed through.

Sydney - (New South Wales). A peak wind gust of 80 km/h occurred at 12.41 pm 16/7/2021 as a front passed through.

THUNDERSTORMS

Thursday evening 15/7/2021, thunderstorm activity passed over areas of the Riverina and South West slopes with Albury Airport recording 20 mm from one event which occurred after sunset.

RAINFALL

To date, the heaviest falls occurred during the 24 hours to 9 am 17/7/2021.

Tooma Dam (NSW) - 82 mm.

Perisha Valley (NSW) - 61 mm.

Geehi (NSW) - 60 mm

(All areas are within the Snowy Mountains of New South Wales and much of this would have been snowfall at higher elevation.)

Black Range (Victoria) - 59 mm.

Harris Lane (Victoria) - 53 mm.

Upper Buckland (Victoria) - 50 mm

(All areas are within the rugged areas of North East Victoria).

Outside the regions, rainfall has been lower but accumulative totals are starting to mount such as 50 mm at Albury Airport.

SNOW

The coldest day so far during the event has been the 17/7/2021 due to the wind direction and snow levels have dropped to quite low levels (Approximately 800 metres above sea level).

Some snowfall has occurred around the Oberon region and the weather station here was reading a temperature of 0.8C at 1.10 pm (17/7/2021).

There have also been snow showers around Canberra and even Blackheath.

While light snows have occurred over the Central Tablelands, heavy snowfalls have occurred across the Snowy Mountains and higher areas of North East Victoria.

SUNDAY TO TUESDAY 18 TO 20 JULY 2021

Conditions are expected to ease as the final front clears the state and passes out into the Tasman Sea.

However, during Tuesday 20 July, a vigorous cold front is forecast to pass over Southern Australia that will re establish the cold conditions over the region. However, this system appears to be even colder as snowfalls are forecast to lower to 500 metres above sea level. Snow may even fall again over the Central Tablelands. This system is expected to be shorter lived than the current system impacting the south.

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