ATL: FIONA - Post-Tropical - Discussion

[chaser1]

12Z Euro takes it to eastern Cuba (so far). Have to watch these sheared storms. The center will follow the convection. If the convection is driven north then that's where the center will go. If all the convection dies out, then the Euro could verify. That's quite a big change from the previous run, so I'd tend not to believe it. It's also too close to the Canadian, which I never believe.

Of course "sheared now" does not necessarily imply "sheared later". That'll be a bigger bridge to cross if it manages to make it over the next 2 or 3

[wxman57]

12Z Euro takes it to eastern Cuba (so far). Have to watch these sheared storms. The center will follow the convection. If the convection is driven north then that's where the center will go. If all the convection dies out, then the Euro could verify. That's quite a big change from the previous run, so I'd tend not to believe it. It's also too close to the Canadian, which I never believe.

Of course "sheared now" does not necessarily imply "sheared later". That'll be a bigger bridge to cross if it manages to make it over the next 2 or 3

Less shear would mean an earlier northward turn.

[SFLcane]

12Z Euro takes it to eastern Cuba (so far). Have to watch these sheared storms. The center will follow the convection. If the convection is driven north then that's where the center will go. If all the convection dies out, then the Euro could verify. That's quite a big change from the previous run, so I'd tend not to believe it. It's also too close to the Canadian, which I never believe.

Of course "sheared now" does not necessarily imply "sheared later". That'll be a bigger bridge to cross if it manages to make it over the next 2 or 3

Less shear would mean an earlier northward turn.

There will be plenty of shear to go around.

[msbee]

Meteo France has us on Yellow vigilance for heavy storms>
https://meteofrance.gp/fr/vigilance/sai ... barthelemy

Vigilance follow-up bulletin for the Northern Islands
Newsletter n°1 - Episode n°8
Issued on Thursday, September 15, 2022 at 12:33 p.m. legal (i.e. 16:33 UTC)
By the Meteorological Center of Guadeloupe

Date and time of the next bulletin: Thursday, September 15 around 6 p.m.

Start of event
Friday, September 16 at 8 a.m.

End of event
Sunday September 18 around 06h.

Current situation
Tropical storm FIONA is located in the Atlantic about 900 km east-south-east of St-Barthélémy.
It is moving west at 22 km/h and should cross the Caribbean Arc tomorrow Friday at the end of the day.
Planned development
Rain :

On Friday, passages of thundery showers are to be expected ahead of the FIONA storm. These showers intensify in the night from Friday to Saturday and remain frequent on Saturday during the day. Cumulations of the order of 50 to 80 mm are possible over the duration of the episode.

Improvement expected on Sunday.

Wind :

Friday during the day, the east-northeast wind strengthens between 40 and 50 km/h on average, then 60 km/h overnight from Friday to Saturday. On Saturday, it turns east-south-east then south-east and drops a notch between 40 and 50 km/h. There is a more moderate southeasterly trade wind on Sunday.

In addition, gusts can reach 80 and 100 km / h, especially during thunderstorms.

Sea :

On Friday, the sea deepened to 3m50 during the day then 4m50 overnight from Friday to Saturday, under the effect of an east-northeast swell then an easterly swell generated by the local wind. Amortization occurs quickly on Saturday during the day.

[CrazyC83]

Recon is flying in at about 925 mb (1,500 feet). They seem to be thinking weak tropical storm with that height. (Usually, a strong tropical storm or low-end hurricane is at 850, a category 2 or stronger is at 700.)

[chaser1]

12Z Euro takes it to eastern Cuba (so far). Have to watch these sheared storms. The center will follow the convection. If the convection is driven north then that's where the center will go. If all the convection dies out, then the Euro could verify. That's quite a big change from the previous run, so I'd tend not to believe it. It's also too close to the Canadian, which I never believe.

Of course "sheared now" does not necessarily imply "sheared later". That'll be a bigger bridge to cross if it manages to make it over the next 2 or 3

Less shear would mean an earlier northward turn.

Typically yes, barring an admittingly long range EURO 500mb and 250mb UL divergence forecast to actually verify.

[chaser1]

Recon is flying in at about 925 mb (1,500 feet). They seem to be thinking weak tropical storm with that height. (Usually, a strong tropical storm or low-end hurricane is at 850, a category 2 or stronger is at 700.)

Any increased distance from convection and decrease in Satellite derived wind speed, and Recon might need to risk getting it's wingtips wet just to measure TS force winds.

[Blown Away]

Very unlikely Fiona will be tightening up and building deep convection around the LLC in the near future. Fiona's LLC has been racing away from the convection to her E all day and I'd say a little faster than the 2pm 14 mph.

[Category5Kaiju]

So let me get this straight: ideally, we would want to have Fiona become stronger more quickly so its chances of recurving are higher? And if it remains weak and disorganized, it would continue more west, which could entail the possibility it develops more futher west (possibly even in the Gulf, assuming it survives a tbd interaction with Hispaniola)?

[SoupBone]

12Z Euro takes it to eastern Cuba (so far). Have to watch these sheared storms. The center will follow the convection. If the convection is driven north then that's where the center will go. If all the convection dies out, then the Euro could verify. That's quite a big change from the previous run, so I'd tend not to believe it. It's also too close to the Canadian, which I never believe.

P.S.

Well, let's just hope the 12Z Euro is out to lunch...

I guess at this point, we'll know when we know. The next several Euro runs will be interesting.

[wxman57]

So let me get this straight: ideally, we would want to have Fiona become stronger more quickly so its chances of recurving are higher? And if it remains weak and disorganized, it would continue more west, which could entail the possibility it develops more futher west (possibly even in the Gulf, assuming it survives a tbd interaction with Hispaniola)?

Correct. Stronger earlier = earlier northwest-north turn. Weaker = farther west and possibly U.S. threat.

[Hammy]

Circulation getting quite elongated today and took a lot more of a beating from the shear than I was expecting.

[aspen]

The exposed center only has a pressure of 1006mb. Either Fiona has weakened, or the NHC’s estimate was too low all day long.

[NotSparta]

The exposed center only has a pressure of 1006mb. Either Fiona has weakened, or the NHC’s estimate was too low all day long.

Estimate was too low. 1002mb always seemed a little sketchy

[Emmett_Brown]

The center is elongated, and per recon, just barely closed. I wonder if we are seeing the beginnings of Fiona opening into a wave (unless the center can reform closer to the convection). Thankfully recon is in there now so we can see the evolution over the next couple of hours.

[Blown Away]

Last visible look at naked Fiona. Fiona's LLC not as tight as earlier.

[skyline385]

Looking at that weakening circulation, i was wondering myself if we see a TD at 5 pm


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[aspen]

The exposed center only has a pressure of 1006mb. Either Fiona has weakened, or the NHC’s estimate was too low all day long.

Estimate was too low. 1002mb always seemed a little sketchy

Turns out 45 kt was spot-on though. Recon found 50kt FL and 45kt SFMR, so the NHC got one part of its intensity estimate right.

[wxman57]

I notice 12Z EC ensembles do not agree with the operational run. They turn it north and keep it east of the U.S., mostly.

https://www.weathernerds.org/tc_guidance/images/AL07_2022091512_ECENS_large.png?1663270910

[skyline385]

The exposed center only has a pressure of 1006mb. Either Fiona has weakened, or the NHC’s estimate was too low all day long.

Estimate was too low. 1002mb always seemed a little sketchy

Turns out 45 kt was spot-on though. Recon found 50kt FL and 45kt SFMR, so the NHC got one part of its intensity estimate right.

So weird seeing 65 kts FL winds on such a sheared system at 1006mb, expect it from systems running polewards but not in the MDR.


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