ATL: HELENE - Post-Tropical - Discussion

[xironman]

This LLC will enter the gulf in excellent conditions, looks pretty vigorous to me

[xironman]

This is a weird development, still looks like the LLC is taking a nosedive, maybe it'll wash out and develop a new one.
https://i.ibb.co/BrnJvKV/giff.gif

FWIW the 12Z GFS does show a SW dive of the LL Circulation in the sort term, then what appears to be a LL reformation to the north later on.


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Exactly what the steering layers predicted.

[aspen]

This LLC will enter the gulf in excellent conditions, looks pretty vigorous to me

https://i.imgur.com/0yK38LS.gif

Gonna need to get tucked back under some persistent convection first, though. That should happen tonight into tomorrow morning if the hurricane models are right.

[Frank P]

This is a weird development, still looks like the LLC is taking a nosedive, maybe it'll wash out and develop a new one.
https://i.ibb.co/BrnJvKV/giff.gif

Not sure where a new one would develop, all the convection to the NE is waning now too. Ironically its the poorest it's looked all day, right after it gets christened lol. This could end up being a significant event in what ends up happening with Helene. I haven't seen a single model, or met, predict this happening.

Maybe this is just a minor deviation, and it will resume its projected track, and that is quite a vigorous LLC.

[Emmett_Brown]

The NHC discussion mentions that Helene’s wind field is expected to be large; “in the 90th percentile”. It would probably be helpful if there were more official graphics products to show the forecasted size of the wind field for storms so people can understand. We all know the cone doesn’t represent where impacts will be felt, but I think most people still think it somehow does. Sure, there are plenty of model outputs of this floating around online, and the new cone sort of shows impacts inland, but in the end, most people just see the old misunderstood cone.

[psyclone]

The NHC discussion mentions that Helene’s wind field is expected to be large; “in the 90th percentile”. It would probably be helpful if there were more official graphics products to show the forecasted size of the wind field for storms so people can understand. We all know the cone doesn’t represent where impacts will be felt, but I think most people still think it somehow does. Sure, there are plenty of model outputs of this floating around online, and the new cone sort of shows impacts inland, but in the end, most people just see the old misunderstood cone.

There are graphics to illustrate the size...the wind probs are displayed as tables and in graphics form in every advisory. I feel they're WAY underutilized

[HurricaneBelle]

The NHC discussion mentions that Helene’s wind field is expected to be large; “in the 90th percentile”. It would probably be helpful if there were more official graphics products to show the forecasted size of the wind field for storms so people can understand. We all know the cone doesn’t represent where impacts will be felt, but I think most people still think it somehow does. Sure, there are plenty of model outputs of this floating around online, and the new cone sort of shows impacts inland, but in the end, most people just see the old misunderstood cone.

<taps the sign> The NHC puts out a wind map which shows the breadth of projected winds, shaded by probability. It's right there on the NHC site under "graphics" and it remains the most underused product they generate. Here's the current one:

[Frank P]

This is a weird development, still looks like the LLC is taking a nosedive, maybe it'll wash out and develop a new one.
https://i.ibb.co/BrnJvKV/giff.gif

FWIW the 12Z GFS does show a SW dive of the LL Circulation in the sort term, then what appears to be a LL reformation to the north later on.


Sent from my iPad using Tapatalk

Exactly what the steering layers predicted.

Well, that might be the case, but I would have assumed the models would have included that prediction in there runs, and I don't recall any model forecast a southerly track at this time.

[Frank P]

FWIW the 12Z GFS does show a SW dive of the LL Circulation in the sort term, then what appears to be a LL reformation to the north later on.


Sent from my iPad using Tapatalk

Exactly what the steering layers predicted.

deleted, thanks for the explanation

[Pipelines182]

This is a weird development, still looks like the LLC is taking a nosedive, maybe it'll wash out and develop a new one.
https://i.ibb.co/BrnJvKV/giff.gif

Not sure where a new one would develop, all the convection to the NE is waning now too. Ironically its the poorest it's looked all day, right after it gets christened lol. This could end up being a significant event in what ends up happening with Helene. I haven't seen a single model, or met, predict this happening.

Maybe this is just a minor deviation, and it will resume its projected track, and that is quite a vigorous LLC.

yeah it's the tightest it's been for sure, I'm doubtful we get a reformation. It's been moving SW for over 2 hours now and the NHC has it pegged at 12 MPH NW. I'm curious how the track will be impacted if it takes longer to get into the GoM than forecasted.

[Ubuntwo]

This is a weird development, still looks like the LLC is taking a nosedive, maybe it'll wash out and develop a new one.
https://i.ibb.co/BrnJvKV/giff.gif

Not sure where a new one would develop, all the convection to the NE is waning now too. Ironically its the poorest it's looked all day, right after it gets christened lol. This could end up being a significant event in what ends up happening with Helene. I haven't seen a single model, or met, predict this happening.

GFS has been depicting a naked swirl for at least part of today consistently. Question is, how long does it stay exposed? Latest run says until 9z tomorrow or so, even the stronger runs had several hours of an exposed circulation. The quicker Helene tightens up the more time for RI.

[ScottNAtlanta]

This is a weird development, still looks like the LLC is taking a nosedive, maybe it'll wash out and develop a new one.
https://i.ibb.co/BrnJvKV/giff.gif

That definitely looks like it is rotating around another center. It should rotate east in the next hour or so. I am wondering what it is rotating around though. It has been moving due south for a while.
Also seeing some hot towers rising on the west side too

[Frank P]

SW dip shows up in the 12z, looks like it last about 6 hours before moving north

[MEANINGLESS_NUMBERS]

The NHC discussion mentions that Helene’s wind field is expected to be large; “in the 90th percentile”. It would probably be helpful if there were more official graphics products to show the forecasted size of the wind field for storms so people can understand. We all know the cone doesn’t represent where impacts will be felt, but I think most people still think it somehow does. Sure, there are plenty of model outputs of this floating around online, and the new cone sort of shows impacts inland, but in the end, most people just see the old misunderstood cone.

<taps the sign> The NHC puts out a wind map which shows the breadth of projected winds, shaded by probability. It's right there on the NHC site under "graphics" and it remains the most underused product they generate. Here's the current one:

https://i.imgur.com/cBivW5M.png

This and the (ugly but highly informative) Wind Arrival Time charts are my staples for hurricane prep.

[Weatherboy1]

Not sure where a new one would develop, all the convection to the NE is waning now too. Ironically its the poorest it's looked all day, right after it gets christened lol. This could end up being a significant event in what ends up happening with Helene. I haven't seen a single model, or met, predict this happening.

Maybe this is just a minor deviation, and it will resume its projected track, and that is quite a vigorous LLC.

yeah it's the tightest it's been for sure, I'm doubtful we get a reformation. It's been moving SW for over 2 hours now and the NHC has it pegged at 12 MPH NW. I'm curious how the track will be impacted if it takes longer to get into the GoM than forecasted.

Put me down for this being a cyclonic loop, one that will be followed by the LLC tucking up under the convection...and a notable change in direction. IOW, this is likely a pre-cursor to a change in path/turn more to the N.

[TampaCE]

of course they will, mandatory evacs and shelters will be in place plus buses can't travel in over 35mph

IMO if i were in charge, i'd wait till tonight or tomorrow 11am.

There’s a chance mandatory evacuations could be called tonight for Zone A. The NHC track currently still has area of Tampa Bay receiving 8 feet storm surge.

And, let me tell you, parents DO NOT like 11 am calls to pick their kids up at school while they’re at work. I know Pinellas here had a meeting at 11, not sure if they have come to a conclusion. But they’re in communication with emergency department here and if they decide to order Zone A evacuation tomorrow, schools will have to be already ready to house residents.

Pinellas schools are closed tomorrow and Thursday and they are monitoring Friday at this time. That was the message we got

[wxman57]

cone moved west. Good news for us.

You can't say its good news at this time. The NHC says future track adjustments may be made in later cycles.

for now it is good news for us at least

The cone is completely irrelevant as far as potential impacts. The cone is the same for every storm, every advisory, no matter the confidence level or the storm size. In this case strong TS and even hurricane wind will extend outside that cone. Some good news for the western FL Peninsula is that the new ICON run is a bit farther west of Tampa. That would keep Tampa out of sustained hurricane force wind, but he area may still see wind gusts 70-85 mph.

[TomballEd]

This LLC will enter the gulf in excellent conditions, looks pretty vigorous to me

https://i.imgur.com/0yK38LS.gif

The storms developing SW of the exposed LLC have their tops being sheared to the NNE. That should slow development at least for a while. OTOH, new convection firing on the SW side may be a bad sign down the road.

[ScottNAtlanta]

SW dip shows up in the 12z, looks like it last about 6 hours before moving north

It looks now to be moving due south, but has slowed like it is about to move east

[ScottNAtlanta]

Shear has dropped quite a bit