Hurricane Ida and Tropical Storm Nora – August 27 2021

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It appears that the Hurricane season is becoming more active across the Americas as two named storms are presently developing and poised to become two separate hurricanes within coming days. The two storms are:-

1 - Tropical Storm Ida

This storm has formed over oceanic waters south of Cuba but the CIMSS models has the storm moving north west towards the coast of Louisiana in coming days. Of interest, the model is suggesting that the storm will make landfall just to the west of the city of New Orleans as a Category 2 Hurricane with peak wind gusts of 95 knots (176 km/h) at the core.

New Orleans suffered greatly in 2005 following Hurricane Katrina (16 years ago) and such a storm will likely test the city once again should landfall occur within the vicinity of the city. The city is built below sea level and is prone to flooding.

This will be an interesting time as the storm develops from a named tropical storm to a hurricane of reasonable strength.  Upon closer view of the matter, the first CIMSS models is suggesting landfall approximately 100 km/h west of the city but models change and the storm direction could also change over time.

Sea surface temperatures are ideal for supporting a strong storm given that temperatures are in the range of 30C to 32C. This storm if it develops further has potential to be a major event in coming days for the state of Louisiana.

A Worldview population plot for the Louisiana coast has been prepared for the area where landfall is forecast to occur. The three main cities are New Orleans, Baton Rouge to the north west and Lafayette to the west. Surrounding the three cities are smaller but sizeable towns. It is clear that the core of the storm is going to pass over or close to three significant cities and a populated coastline with New Orleans at greatest risk from the event.

The second Worldview image is showing the location of storm over southern Cuba and close to Jamaica which is the storm that is forecast to intensify in coming days.

2 - Tropical Storm Nora

This storm has formed off the west coast of Mexico and is still developing. There have been a number of recent hurricanes forming off the west coast of Mexico within this area but these have formed then decayed out over open oceans. The storms have not impacted land and have had no impact to any population centre. Such storms have died out over colder waters of the Pacific Ocean.

This storm appears to be different to previous storms because the CIMSS model is showing Tropical Storm Nora as taking a completely different path along and off the west coast of Mexico before making landfall across Southern Baja California.

The CIMSS model shows the storm developing into a Category 1 hurricane with peak wind gusts to 75 knots (139 km/h) prior to landfall. Again, ocean temperatures in this part of the Pacific Ocean are around the 29C to 31C and also capable of sustaining a strong storm.

Southern Australia – Strong cold front – 2 and 3 September 2021

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Following a warm spell which has seen temperatures reach into the low 30s across parts of Western New South Wales and north west Victoria, a strong cold front is now making its way across southern Australia.

Much like a similar recent frontal system, the air ahead of the change is relatively warm. In Mildura (NW Victoria), it reached 32.7C on the 2 September 2021 and an overnight minimum of 21.7C was recorded at 8 am 3/9/2021. The weather station here recorded a maximum peak temperature of 25.1C at 10 am for the 3/9/2021. By 3 pm after the change has passed, the temperature had fallen to only 13.3C.

Other warm temperatures for early September (September 2 2021) has included:-

• Loxton (South Australia) - 33.2C.
• Swan Hill (NW Victoria) - 31.2C.
• Broken Hill (Far Western New South Wales) - 31.3C.
• Deniliquin 28.2C and 28.5C on the 3/9/2021 before the change arrived.

The cold change is having a strong impact on maximum temperatures ahead and after the change. A rain band with some thunderstorm activity is being pushed east with the front which has brought some reasonable rainfall of between 30 mm and 40 mm within areas north and north east of Melbourne.
The change will progress further east reaching Sydney Saturday afternoon.

 

The change has brought wind gusts to 96 km/h at Falls Creek and 104 km/h at Mt Buller at 1.12 pm 3/9/2021.

Maximum rainfall from this event are not expected to be significant for Sydney but for North East Victoria and Eastern Victoria, maximum rainfall figures are forecast to be in the range of 50 mm to 100 mm and 25 mm to 50 mm within adjacent areas including southern New South Wales.

The main concern is snow melt as a result of the rain. This could result in some flooding of rivers and with Lake Hume at close to 95% full, there is a risk of some riverine flooding along the Murray River in coming days from this event.

Addendum

The change brought some significant rainfall across the hilly areas of North East Victoria, the South West slopes close to the Great Dividing Range and Eastern Victoria.

Within these areas, daily rainfall totals topped between 50 mm and 100 mm. It is identified that the rain coupled with the snowmelt has generated minor flood warnings along certain rivers including the Kiewa and Ovens River and Murray River upstream of the Hume Reservoir dam wall. This will require water releases from the Hume Reservoir which is at 95% capacity. This will benefit farmers downstream including irrigators.

The change reached Sydney during Saturday afternoon however its impact was relatively mild. It brought rainfall of between 3 mm and 20 mm with the lesser totals being around Penrith and Richmond.

Another Atlantic Hurricane named Larry – Friday 3 September 2021

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Following the demise of Hurricane Ida which has had a catastrophic impact from New Orleans to New York with numerous fatalities from storms and flooding, another named storm has developed within the Central Atlantic Ocean which is going to start to approach the eastern coastline of the United States in coming days.

However, weather models presently suggests that the storm will curve more towards the north in coming days and then decay out over open ocean.

Hence this storm should only disrupt shipping lanes and certain flights within the vicinity of the storm.

The new storm has been named Larry which has intensified rapidly to a Category 2 storm on the Saffir Simpson Scale.

Given the level of storm damage that has occurred across large areas of the southern and eastern United States in recent weeks, authorities will be monitoring this storm closely.

The storm is forecast to reach as high as a category 4 storm on the Saffir Simpson Scale with peak wind gusts to 120 knots or 222 km/h.

The storm is currently sustaining peak winds of up to 100 knots (185 km/h) at the core. It is a well developed storm with strong convection evident.

The storm is presently tracking north west at 14 knots (26 km/h).

Should the CIMSS and National Weather Service models prove correct, then this should not make landfall and should decay out over open ocean.
The images of the storm is derived from CIMSS, satellite imagery and NASA (Worldview 4/9/2021).

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