ATL: ISAIAS - Post-Tropical - Discussion

[tiger_deF]

It's still an unholy mess. Two separate MLCs, each literally hundreds of miles from the LLC, with the weaker (trailing) MLC closer. I assume they're calling it a tropical cyclone because it's going to bring TS conditions to the Lesser Antilles in spite of epic misorganization. I suppose you could view it as a bizarre subtropical storm, since MLC and LLC don't have to be aligned for those.

While it is absolutely disorganized, I would say it's sprawling size is actually the reason it is still alive today; I doubt a Gonzalo sized storm would have been able to fight off enough dry air to maintain any convection at all. The next 24-48 hours are going to be crucial.

[Hypercane_Kyle]

It's still an unholy mess. Two separate MLCs, each literally hundreds of miles from the LLC, with the weaker (trailing) MLC closer. I assume they're calling it a tropical cyclone because it's going to bring TS conditions to the Lesser Antilles in spite of epic misorganization. I suppose you could view it as a bizarre subtropical storm, since MLC and LLC don't have to be aligned for those.

They're not calling it a tropical cyclone. This is a potential tropical cyclone (PTC).

[Jr0d]

Sometimes with a large tropical wave, the energy splits and two storms develop. This might be possible here, with the area south and east being the promary concern for now, while the area further northwest may do something later but much more likely to stay out to sea.

While I dont think this is a likely solution with this wave, I do think it is a realistic possibility.

[PTrackerLA]

 https://twitter.com/TropicalTidbits/status/1288137701380718597

[Shell Mound]

IMO, I think this'll become a minimal hurricane in the Bahamas. Perhaps something similar to Erin in 1995. I think the global models are struggling to consolidate this one correctly, given its broad and generally speaking disorganized state.

Erin 1995 could be an analog but does anyone remember how they were forecasting Erika in 2015 to strike the East Coast of Florida as a minimal hurricane and it failed to do so? Similar location, track, and speed.

https://i.ibb.co/QMdhgsH/D0-FFBF8-F-7-B42-4182-9790-73-DFF22-ED413.jpg

...and that’s the double-edged sword at play, especially when dealing with similarly uncertain forecasts. Hypothetically, this could just as easily be the “anti-Erin”: forecast to be only a moderate, sloppy tropical storm at best, but ends up as something far more intense than initially expected. Given the uncertainty, we wouldn’t necessarily know the outcome until the last minute, or nearly so, and given a “high-risk” situation, the difference between a dud and a disaster is stark but thin. My earlier gist still stands. The fact that this system is holding its own through the diurnal minimum could be an early warning signal.

[MississippiWx]

For now, the southwestern piece is most dominant. There are southerly winds bisecting the two areas of spin with the southwestern area looking much more ready to become a tropical cyclone. This will more than likely give models fits.

[Vdogg]

Sometimes with a large tropical wave, the energy splits and two storms develop. This might be possible here, with the area south and east being the promary concern for now, while the area further northwest may do something later but much more likely to stay out to sea.

While I dont think this is a likely solution with this wave, I do think it is a realistic possibility.

I think you mean South and West is primary concern and northeast is later. There’s also an interesting piece of energy to the east of all this mess as well. Also something funky going on along the NC/SC border (still can’t figure out how to post a gif). Gonna be an interesting few days seeing how all these features interact.

[GCANE]

Here we go!!

Where we going?

Covid and a TS oh man get ready for major shortages in food and supplies. Can’t even rap my head around it

A prelude of more to come???

[Ian2401]

 https://twitter.com/splillo/status/1288125928371937282

[Aric Dunn]

I see the southern circ is becoming much more defined and circular.

way more SE inflow into it.

I would not be surprised if recon found a good well defiend llc.

Currently little to no dry air will be able to penetrate the deep moisture flux.

models are almost certainly over doing the dry air.

[aspen]

https://twitter.com/splillo/status/1288125928371937282

That high already? I think that’s higher than any RI probability SHIPS gave Hanna.

[Shell Mound]

https://twitter.com/splillo/status/1288125928371937282

Follow-up:

 https://twitter.com/splillo/status/1288126423631163392



 https://twitter.com/splillo/status/1288130204540387328



 https://twitter.com/tammy_conklin/status/1288127625500569602



 https://twitter.com/KeviShader/status/1288126439657598980

[bqknight]

What are the models seeing in/near the Bahamas that is prohibiting strengthening?

[GCANE]

What are the models seeing in/near the Bahamas that is prohibiting strengthening?

GFS is showing a big upper-level jet over it.

[TheStormExpert]

Does the NHC take into consideration that PTC-9 is trucking west with no change in direction? There forecasting it to abruptly turn WNW which seems highly unlikely.

[DestinHurricane]

What model run will recon data be in models?

[Hurricaneman]

What are the models seeing in/near the Bahamas that is prohibiting strengthening?

Stable air

[Aric Dunn]

Shear forecast from the models once north of Hispaniola are also probably way over blown( pun intended)

this will be a large heavy convection producing system and models always have issues with shear in scenarios like this where the shear is coming from a smaller scale mid to upper level feature pushing against a lot of outward pressure from the system.

with plenty of moisture in a huge pouch dry air wont be an issue once this becomes more established at the surface.

[RT23]

WOW 65kt winds....

[RT23]

15:59:00Z 15.733N 57.133W 689.6 mb
(~ 20.37 inHg) 3,298 meters
(~ 10,820 feet) 1010.3 mb
(~ 29.84 inHg) - From 76° at 64 knots
(From the ENE at ~ 73.6 mph) 10.6°C
(~ 51.1°F) -1.3°C
(~ 29.7°F) 65 knots
(~ 74.8 mph)