Hurricane Ida – A major storm at landfall – 29 and 30 August 2021

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Hurricane Ida has made landfall as a major hurricane as forecast although it is noted that just prior to landfall peak wind gusts were estimated at close to 130 knots (241 km/h).

The outer storm bands first hit the Mississippi River Delta region and later metropolitan New Orleans before spreading onshore across the region.

It is clear that Ida reached Category 4 on the Saffir Simpson Scale. Measurements taken demonstrate that this storm was vertically deep and intense. Doppler radar velocity data from Slidell suggested 130 knot winds (241 km/h) between 7.5 to 9 km above sea level and it attained a clear eye of approximately 28 km in diameter.

The storm has brought destructive winds and rain.

It is presently difficult in obtaining actual data from weather stations due to large areas being impacted by significant power loss however it is known that a weather station north of the city centre of New Orleans (Lakefront Airport) recorded a peak wind gust of 86 mp/h (Converted to 138 km/h). It is presently difficult to obtain verified data close to the area where the eye crossed due to significant damage to electrical grids and related infrastructure.

Even obtaining rainfall data is difficult for the same reason. However, it is known to date to 7 pm 29 August 2021:-

Slidell NE of New Orleans recorded 100 mm.
New Orleans City centre – A rain gauge recorded 91.6 mm.
Port of South Louisiana - 125.2 mm.

These are converted from inches as the NWS uses inches. However since that time more significant rainfall has occurred because there is significant low lying flooding in many areas.

The plot prepared on the NWS to 7 pm 29/8/2021 shows isolated areas receiving upwards of 100 to 125 mm within New Orleans including two other areas outside the city.

Much heavier rain would have occurred since that time.

CNN is reporting approximately 1.1 million residents without power, 1 fatality to date and numerous roads impassible. It is too early to know what is going on due to continuing impacts the storm is having.

It is known that the eye wall passed 40 km west of New Orleans.

An Image from GOES 16 (Available via the National Weather Service) shows an intense storm and a clear eye. This storm is at its peak being a Category 4 system on the Saffir Simpson Scale and just before landfall. A second image is attached following landfall showing a weakening storm.

There is no doubt that over coming days, damage assessments will be under way and search and rescue operations commencing. There is anecdotal evidence that this is going to be a very costly event once the true impacts of the storm is known.

At the time of writing, Hurricane Ida is no more having weakened to a tropical storm as it slowly moves north east across the Mississippi Valley.

Hurricane Ida before landfall – 29 August 2021

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Hurricane Ida is now approaching the state of Louisiana as a Category 3 storm on the Saffir Simpson Scale and expected to intensify further to a Category 4 storm shortly.

Models do anticipate landfall close to Morgan City Louisiana as a Category 4 storm.

A national weather service radar image is beginning to show the storm more clearly as it approaches full radar coverage of the National Weather Service. An eye can now be delineated and satellite photos also shows a small eye at its centre.

As at 11.31 am Sunday morning (Sydney time), the first outer storm bands are beginning to make landfall over the Mississippi River delta south east of New Orleans and a band of thunderstorms are approaching land east of New Orleans but south of Pensacola (Florida Panhandle).

A low level 3D image of the forecast landfall site has been prepared using Google Earth Experimental 2021. The expected coastal landfall site based on current weather models comprises mainly of swamp marshland, low lying river mudflats and areas that are easily prone to flooding. The closest towns are slightly to the north including Amelia, Morgan City, Bayou Vista, Patterson, Franklin, Baldwin. The closest major city on the forecast path is Lafayette. As shown on Google Earth Experimental in 3D, Lafayette is a major population centre but is low lying and also prone to flooding. The city is expected to suffer a major impact in terms of flooding, tree damage and damage to buildings.

Another major city expected to suffer a significant impact is Baton Rouge which is a larger city than Lafayette. As shown in 3D Google Earth Experimental 2021, the city lies on the Mississippi River and the region comprises mudflats and low level swampland, marshland or just low level flood prone land. Flooding would be extensive for this region.

New Orleans is shown in 3D. Whatever flooding occurs at Baton Rouge will impact New Orleans as the city is downstream on the Mississippi River and in 2005, experienced catastrophic flooding from Hurricane Katrina.

The whole region is flood prone and hence, flooding is expected to be considerable.

A storm surge and flooding of 3 metres is now being forecast.

News reports suggest that some areas could be made uninhabitable for a while due to the strength of the storm and expected damage. Evacuations are occurring ahead of the storm.

Hurricane Nora

Hurricane Nora is currently off the west coast of Mexico and has reached hurricane status (Category 1 on the Saffir Simpson Scale). Recent weather models have suggested an altered course. As such, the storm appears to parallel the Mexico coastline and should cross the coast east of Baja California. The expected landfall site would be in the vicinity of Guaymass.

The storm is not as well developed when compared to Hurricane Ida but given its proximity to the Mexican coastline, the storm may not last as long as forecast as the Mexican landmass will impact on its strength over coming hours / days.

Addendum - Shortly after posting this status, the storm made landfall that brought heavy rain and local flooding and the storm decayed into a rain depression.

Hurricane Ida Intensifies 28 August 2021

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Tropical Storm Ida has intensified rapidly into a Category 2 storm with peak wind gusts to 85 knots (158 km/h) at the core. The storm reached hurricane status as it passed over the western coastline of Cuba before moving off the coast. The storm is now at or just above a category 2 system on the Saffir Simpson Scale.

The CIMSS models have upgraded this storm further and the potential exists for a Category 4 storm on the Saffir Simpson Scale prior to landfall. In this regard and just prior to landfall over the Louisiana coast, the storm will have the potential to be packing winds of 120 knots (222 km/h) at the core.

The storm will be supported by waters that have been heated to 31C.

At the present time, the storm is taking on a spiral appearance as it intensifies. To date, this will become the strongest storm this season for the region and the storm will have potential to cause significant wind and flood damage at landfall.

As at 2 am EDT (US time), the storm was moving at 13 knots (24 km/h) towards the north-west and the forecast cone from the National Weather Service 27/8/21 is showing landfall over the Louisiana coast just to the west of New Orleans. Landfall is expected on Sunday morning.

Likely rainfall totals are forecast to reach in excess of 250 mm around New Orleans increasing to 350 mm for areas situated further west.

The radar image for the region is also attached and while the storm is not fully visible, its location is evident by the storm and rain bands just off the west coast of Florida.

Significant warnings and alerts have now been issued as significant wind damage is being forecast in areas where landfall is likely and such warnings cover New Orleans. Such warnings include necessary evacuation and preparation orders.

A closeup wind threat map from the (National Weather Service) shows the expected winds and areas that are likely to be most impacted by this event and it becomes clear that Baton Rouge, Lafayette and New Orleans are the population centres most at risk. However, Morgan City is now being suggested as the closest city where landfall is expected based on current models.

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