ATL: HELENE - Models

[shah83]

12z Euro is pretty far west. Would involve Tallahassee and Atlanta again...

[Nederlander]

12z Euro run seems pretty locked in on a Cat 2 at landfall. Realistic projection here.

https://i.ibb.co/55RxLQK/9-km-ECMWF-Global-00z-12z-3-Hourly-Gulf-of-Mexico-MSLP.gif

Euro is once again underestimating strength... don't trust it, it's trash

[BobHarlem]

closest before landfall 12z euro frame

[DunedinDave]

12z Euro is pretty far west. Would involve Tallahassee and Atlanta again...

It's almost identical to 0z and 6z track. Don't really see any move west.

[ronjon]

12z Euro pretty much consistent with forecast track the last 2 days. Pressure at landfall has gradually dropped from 984 mb at 00z, to 982 mb at 06z, and now 976 mb at 12z.

[Steve]

12z Euro run seems pretty locked in on a Cat 2 at landfall. Realistic projection here.

https://i.ibb.co/55RxLQK/9-km-ECMWF-Global-00z-12z-3-Hourly-Gulf-of-Mexico-MSLP.gif

Yeah that does seem pretty reasonable. @ 500 you can see how the trough grabs it and sets up for the next several days over the SEUS. However it gets replaced by a ridge at the end of the 10-day period.

https://www.pivotalweather.com/model.ph ... ecmwf_full

[Steve]

Here's the early cycle intensity guidance for 18z.

[Steve]

And early cycle 18z track guidance

[StPeteMike]

And early cycle 18z track guidance

https://hurricanes.ral.ucar.edu/realtime/plots/northatlantic/2024/al092024/track_early/aal09_2024092418_track_early.png

Wow, first time seeing the accelerated right hooks on some of them. How good is TABS, Steve? I feel like I have fond memories of seeing people TABS is pretty reliable, but you are fine to correct me if wrong. And clearly, it’s one of many.

[Steve]

And early cycle 18z track guidance

https://hurricanes.ral.ucar.edu/realtime/plots/northatlantic/2024/al092024/track_early/aal09_2024092418_track_early.png

Wow, first time seeing the accelerated right hooks on some of them. How good is TABS, Steve? I feel like I have fond memories of seeing people TABS is pretty reliable, but you are fine to correct me if wrong. And clearly, it’s one of many.

They aren't useful (maybe barely) for track purposes. They follow the wind/shear and are Trajectory based as opposed to dynamical, consensus or statistical. They're barely better than Clipper in my opinion (probably worse sometimes). TWC has a page on these which references: Some models just follow the winds, and they are collectively known as the TABs (or Trajectory and Beta Models). These three models - shallow, medium and deep - are slightly more useful (than CLIP/XTRAP) because the closer they are together, they indicate that there is less wind shear in the atmosphere. On the contrary, if they are spread out, this is indicative that there is more wind shear and the system will likely stay weak. A weak system should not be monitored using the deep version of the TABs called TABD since those systems do not tap the upper portions of the atmosphere. Here's a link to the their article from 2022, "Hurricane Spaghetti Models: Four Things You Need to Know to Track Storms Like the Pros."

It's pretty educational, short and worth anyone's 5 minutes to read or even a favorites link for future reference.

https://weather.com/science/weather-exp ... -hurricane

[DunedinDave]

A lot of those 18z models are left of the NHC forecast in the short term and Helene itself seems slightly right of the NHC short-term forecast. Again, every wobble moving forward makes a ton of difference.

[Steve]

^^ Note the "ICON" in TWC's list is a different ICON and not the German model we run on here all the time.

[Powellrm]

Whoa ICON ratcheting up a bit with a 947 nearly upon landfall in the big bend area before crushing Georgia, upstate SC, and western NC. Wow. Asheville NC getting rain prior to the storm as well. Major flood watch.

[Steve]

Whoa ICON ratcheting up a bit with a 947 nearly upon landfall in the big bend area before crushing Georgia, upstate SC, and western NC. Wow.

You looking at the 12z? That one has some 2 feet rain totals across all of WNC and W SC. 18z will be out in an hour or so but it only goes 5 days.

[Powellrm]

Whoa ICON ratcheting up a bit with a 947 nearly upon landfall in the big bend area before crushing Georgia, upstate SC, and western NC. Wow.

You looking at the 12z? That one has some 2 feet rain totals across all of WNC and W SC. 18z will be out in an hour or so but it only goes 5 days.

Yes. ICON is every 6 hours I believe? Absolutely devastating. If the ridge isn’t as prominent, and it drifts farther east into central NC-I’m in trouble. I just filled a bunch of sandbags today just in case.

[Powellrm]

And early cycle 18z track guidance

https://hurricanes.ral.ucar.edu/realtime/plots/northatlantic/2024/al092024/track_early/aal09_2024092418_track_early.png

Wow, first time seeing the accelerated right hooks on some of them. How good is TABS, Steve? I feel like I have fond memories of seeing people TABS is pretty reliable, but you are fine to correct me if wrong. And clearly, it’s one of many.

They aren't useful (maybe barely) for track purposes. They follow the wind/shear and are Trajectory based as opposed to dynamical, consensus or statistical. They're barely better than Clipper in my opinion (probably worse sometimes). TWC has a page on these which references: Some models just follow the winds, and they are collectively known as the TABs (or Trajectory and Beta Models). These three models - shallow, medium and deep - are slightly more useful (than CLIP/XTRAP) because the closer they are together, they indicate that there is less wind shear in the atmosphere. On the contrary, if they are spread out, this is indicative that there is more wind shear and the system will likely stay weak. A weak system should not be monitored using the deep version of the TABs called TABD since those systems do not tap the upper portions of the atmosphere. Here's a link to the their article from 2022, "Hurricane Spaghetti Models: Four Things You Need to Know to Track Storms Like the Pros."

It's pretty educational, short and worth anyone's 5 minutes to read or even a favorites link for future reference.

https://weather.com/science/weather-exp ... -hurricane

Hey Steve thanks for posting this! Great read.

[robbielyn]

Ryan Maue: Last updated model to arrive for 12z is the ecmwf hres and it shows a rather disheveled Helene at 975 mb cat 2+. However, wind shear from a upper-level trough to the wnw may keep from maximum potential.

[Zonacane]

Ryan Maue: Last updated model to arrive for 12z is the ecmwf hres and it shows a rather disheveled Helene at 975 mb cat 2+. However, wind shear from a upper-level trough to the wnw may keep from maximum potential.

I would never recommend using the Euro to gauge intensity. There are a multitude of Well-known biases and resolution issues

[Steve]

Wow, first time seeing the accelerated right hooks on some of them. How good is TABS, Steve? I feel like I have fond memories of seeing people TABS is pretty reliable, but you are fine to correct me if wrong. And clearly, it’s one of many.

They aren't useful (maybe barely) for track purposes. They follow the wind/shear and are Trajectory based as opposed to dynamical, consensus or statistical. They're barely better than Clipper in my opinion (probably worse sometimes). TWC has a page on these which references: Some models just follow the winds, and they are collectively known as the TABs (or Trajectory and Beta Models). These three models - shallow, medium and deep - are slightly more useful (than CLIP/XTRAP) because the closer they are together, they indicate that there is less wind shear in the atmosphere. On the contrary, if they are spread out, this is indicative that there is more wind shear and the system will likely stay weak. A weak system should not be monitored using the deep version of the TABs called TABD since those systems do not tap the upper portions of the atmosphere. Here's a link to the their article from 2022, "Hurricane Spaghetti Models: Four Things You Need to Know to Track Storms Like the Pros."

It's pretty educational, short and worth anyone's 5 minutes to read or even a favorites link for future reference.

https://weather.com/science/weather-exp ... -hurricane

Hey Steve thanks for posting this! Great read.

Yeah word. Any non-met should read that so when we post the early and late cycle tracks and intensity tracks there's a reference point to what the specific models are actually useful for.

[Travorum]

18z ICON is running on pivotal weather, initialized at 1000mb roughly where the 12z forecast it.