Friday, August 28, 2020

Tropical Depression Laura: August 27, Update A

What a difference a day makes! One day your lawn is pristine, the next it's covered with debris!

Hurricane Laura is now a Tropical Depression, officially visiting Arkansas. She's currently at 35.1N, 92W, heading NNE at 15mph: 

Winds are now 35mph, central pressure is 993mb. She still has good vorticity (circulation) in the lowest level of the troposphere. Although there is a lot of vorticity in the middle level, it is spread out over a larger area, so I would agree with the strong Tropical Depression status. You can see that her convection is diminishing quite rapidly in the upper left corner of this imagery:

Given how much vorticity is in the system, I agree that it looks like she'll be a windy things as she visits Kentucky and West Virginia at least. 

She didn't cause the storm surge one may sometimes see with a strong cat 4 on landfall. In Lake Charles, the surge was less than 5ft and in Cameron, LA (very near landfall and closer to the coast), the surge was just under 9ft instead of the 15-20ft that was predicted. This is because the angle of approach of the storm, the speed the storm is moving at, the angle of the coastline (and estuary), and the side of the storm you are on all play into the storm surge. 

She caused some damage in some places, but it could have been considerably worse! The damage for a cat 4 (by definition) by the way includes "well-built framed houses sustaining severe damage with the loss of most of the roof structure and some exterior walls, most trees are snapped or uprooted and power poles are down which means power outages can last for weeks (or months). Most of the area should be uninhabitable for weeks following a cat 4 storm." The power lines were certainly knocked down and I read that around 900,000 people are without power. One thing that kept the damage down is that she made landfall in a relatively sparsly populated area and may have weakened just enough by the time she got to the town of Lake Charles, where the airport recorded sustained winds of 98mph - cat 2 status - with gusts of 132mph (and although gusts don't count towards the category, that's in the weak cat 4 level). 

Alas, there were some fatalities - in the US and even more in the Caribbean. I fully expect that she will be retired after this season and we won't see another tropical storm named Laura.

She was certainly a strong storm, but not the strongest storm to hit the northern Gulf. Hurricane Camille, which also made landfall in the northern Gulf in 1969 (51 years ago), still holds the title of the strongest storm to ever hit the US (estimated winds were around 175mph). Camille's storm surge was 24ft...although a side note that Hurricane Katrina (a cat 3 storm) had a higher surge of around 30ft (again - it's not the intensity of the storm alone that determines the surge). 

I'll be back tomorrow... I don't think I've ever talked about Kentucky in the context of a storm before! 

Toodle pip,


Twitter: jyovianstorm

These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and local weather service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know. 

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