ATL: LAURA - Post-Tropical - Discussion

[sponger]

Just booked 5 nights in San Antonio Hilton starting Thursday.

Seems a bit late to miss storm, but may allow you to miss a extended power outage. Tuesday looks best now but predicted arrival time of hurricanes is still stuck in the 19th century.

[eastcoastFL]

Now that we have a good amount of Louisiana folks on the board what effects would a land falling cat 3/4 west of NOLA have on the city? I just keep thinking of how awful evacuations were with Katrina and how in the world they would handle this with Covid. I guess you can’t exactly squeeze everyone into the Saints stadium this time around. Do they have contingency plans in place already?

[EnnisTx]

It’s late August, water 90, this will be cat 3/4 mark it down

If I had to stick my neck out and make a prediction, which I really hate doing because it's always just a crapshoot, I'd bet on a Cat 4 through the Gulf and landfalling as a Cat 3

I am going with a strong cat 4 into east-central LA coast.

I don't see Laura going into East Central Louisiana at this point I wouldn't be surprised if it's more towards Galveston in the end. What strength? Who knows it could get ugly though.

[Kazmit]

While the storms are different and headed on their own unique paths, the scene in the western Atlantic this morning is remarkably reminiscent of a similar scene in August 2004, with storms at similar intensities.

4.8 MB. Source: Bonnie/Charley image from the now defunct website Operational Significant Event Imagery. RGB composite of Marco and Laura made using data from NASA MSFC.
https://i.imgur.com/gigRAcu.png

Wow, nice use of the exact same satellite imagery. I couldn't even tell one was from 2004 and the other from 2020.

[Aric Dunn]

[PTrackerLA]

Laura has me concerned in Lafayette. Went to the store yesterday and will try to wrap up preps outside during the breezes from Marco tomorrow . This is probably the greatest threat to SE TX and SW/SC LA since 2008.

[eastcoastFL]

Looking favorable up above



And down below

[ronjon]

Right, and I guess that's my point. Following in Marco's weakness, at least mostly, would still lend itself to a Central Louisiana solution unless the ridge builds back in faster than expected behind Marco. So Marco's timing and placement will be key to Laura's ultimate arrival track.

"unless the ridge builds back in"
That is exactly what the Euro is forecasting. It seems to have a better grasp than the GPS on the more Southern track over Cuba and may end up nailing the expanding ridge as well.

“Unless the ridge builds back in...”

Will Marco “push” the ridge?
Will he “punch” through it?

I don’t understand how that happens. I don’t remember hearing about this phenomenon before.

I thought a hurricane has to “run around” and was “steered”. By a HP ridge.

I thought a ridge builds or recedes based on jet stream movement?

Can someone enlighten me what this means and how it works?

Strong ridges do steer tropical systems, even the most intense. Physics makes tropical cyclones always want to go poleward (north) once they reach mid-latitude westerlies (higher atmospheric winds that move most systems from west to east). Strong ridging can prevent that northward path. The discussion with this storm is that other tropical systems near the pathway of Laura could be strong enough (up into the midlevels of the atmosphere) to temporarily weaken the western edge of the Atlantic ridge...enough to cause Laura to feel that weakness and move into it...at least for a short period of time. Its temporary though as the other system is moving or can weaken, which would allow the western extension of the ridge to build back in.

[Nimbus]

I'm thinking about a worst case scenario where the LLC smashes itself against the hight terrain on the eastern side of Cuba, after which a new one forms under the convection of the MLC and the system goes just south of Cuba over the extremely warm waters there. Not saying this will happen, just a hypothetical scenario that seems possible to me.

Macaya mountain range looks like it has tightened up the center just a few miles north off the coast.
That *might* mean a track a little further south of Cuban coastline with more time to strengthen next update.
Laura probably isn't in the mood for a rapid spin up after trekking over the mountains but if she were stronger she might take a slightly more poleward wobble earlier.
A lot to watch, recon has been a huge help finding these vorts!

[Aric Dunn]

West it is.. and wrapping up fast.. if it does not start moving north of west it will just clip the SW portion of the mountains..

[St0rmTh0r]

This year will be one for the books. Laura taking path of least resistance. Cant believe it managed to organize over land now it's over water. If I lived in the path of this I'd leave.

[shah83]

And that close to the radar tower probably means we are looking at the low level center.

[ronjon]

I think since Laura is relatively weak shes getting pushed hard by strengthening ridge to the north. Ridge is probably pretty strong at both low and midlevels. She'll probably remain pretty blob-like until reemergence off the NW tip of Cuba.

[St0rmTh0r]

I'm thinking about a worst case scenario where the LLC smashes itself against the hight terrain on the eastern side of Cuba, after which a new one forms under the convection of the MLC and the system goes just south of Cuba over the extremely warm waters there. Not saying this will happen, just a hypothetical scenario that seems possible to me.

Macaya mountain range looks like it has tightened up the center just a few miles north off the coast.
That *might* mean a track a little further south of Cuban coastline with more time to strengthen next update.
Laura probably isn't in the mood for a rapid spin up after trekking over the mountains but if she were stronger she might take a slightly more poleward wobble earlier.
A lot to watch, recon has been a huge help finding these vorts!

How do the mountains tighten up the center? Can someone explain how this process works? I always see people mentioning this

[Tireman4]

A developing and organizing TC over Hispaniola!? 2020 never ceases to surprise! And to think a few days ago I was starting to write this storm off due to its very crappy appearance.

All in all it looks like a major hurricane landfall is becoming more and more likely for someone along the U.S. Gulf Coast mid-week.


https://s7.gifyu.com/images/goes16_vis_13L_202008231132.gif

I don’t think I’ll be writing off any storms until they actually dissipate. Anything is possible during peak season

Indeed. Dr. Neil Frank has said this over and over and over!!

[Nederlander]

I'm thinking about a worst case scenario where the LLC smashes itself against the hight terrain on the eastern side of Cuba, after which a new one forms under the convection of the MLC and the system goes just south of Cuba over the extremely warm waters there. Not saying this will happen, just a hypothetical scenario that seems possible to me.

Macaya mountain range looks like it has tightened up the center just a few miles north off the coast.
That *might* mean a track a little further south of Cuban coastline with more time to strengthen next update.
Laura probably isn't in the mood for a rapid spin up after trekking over the mountains but if she were stronger she might take a slightly more poleward wobble earlier.
A lot to watch, recon has been a huge help finding these vorts!

How do the mountains tighten up the center? Can someone explain how this process works? I always see people mentioning this

Friction. Same thing happens when a storm makes landfall, even in flat areas. You can often see the eye contract as it nears the coast, like it’s being squeezed.

[NevadaFan18]

https://twitter.com/andyhazelton/status ... 43872?s=21

[Nimbus]

I'm thinking about a worst case scenario where the LLC smashes itself against the hight terrain on the eastern side of Cuba, after which a new one forms under the convection of the MLC and the system goes just south of Cuba over the extremely warm waters there. Not saying this will happen, just a hypothetical scenario that seems possible to me.

Macaya mountain range looks like it has tightened up the center just a few miles north off the coast.
That *might* mean a track a little further south of Cuban coastline with more time to strengthen next update.
Laura probably isn't in the mood for a rapid spin up after trekking over the mountains but if she were stronger she might take a slightly more poleward wobble earlier.


A lot to watch, recon has been a huge help finding these vorts!

How do the mountains tighten up the center? Can someone explain how this process works? I always see people mentioning this

The 8000 foot mountains create a sort of wind tunnel for those winds on the south side of the circulation in this case increasing the spin rate of the core winds.

[Visioen]

I'm thinking about a worst case scenario where the LLC smashes itself against the hight terrain on the eastern side of Cuba, after which a new one forms under the convection of the MLC and the system goes just south of Cuba over the extremely warm waters there. Not saying this will happen, just a hypothetical scenario that seems possible to me.

Macaya mountain range looks like it has tightened up the center just a few miles north off the coast.
That *might* mean a track a little further south of Cuban coastline with more time to strengthen next update.
Laura probably isn't in the mood for a rapid spin up after trekking over the mountains but if she were stronger she might take a slightly more poleward wobble earlier.
A lot to watch, recon has been a huge help finding these vorts!

How do the mountains tighten up the center? Can someone explain how this process works? I always see people mentioning this

I believe it is because of frictional convergence. http://glossary.ametsoc.org/wiki/Frictional_convergence

[Michele B]

"unless the ridge builds back in"
That is exactly what the Euro is forecasting. It seems to have a better grasp than the GPS on the more Southern track over Cuba and may end up nailing the expanding ridge as well.

“Unless the ridge builds back in...”

Will Marco “push” the ridge?
Will he “punch” through it?

I don’t understand how that happens. I don’t remember hearing about this phenomenon before.

I thought a hurricane has to “run around” and was “steered”. By a HP ridge.

I thought a ridge builds or recedes based on jet stream movement?

Can someone enlighten me what this means and how it works?

Strong ridges do steer tropical systems, even the most intense. Physics makes tropical cyclones always want to go poleward (north) once they reach mid-latitude westerlies (higher atmospheric winds that move most systems from west to east). Strong ridging can prevent that northward path. The discussion with this storm is that other tropical systems near the pathway of Laura could be strong enough (up into the midlevels of the atmosphere) to temporarily weaken the western edge of the Atlantic ridge...enough to cause Laura to feel that weakness and move into it...at least for a short period of time. Its temporary though as the other system is moving or can weaken, which would allow the western extension of the ridge to build back in.

That makes sense!

Thanks. ron!!!