ATL: BILL - Post-Tropical - Discussion

[Subtrop]

93L INVEST 210614 0000 32.3N 77.1W ATL 20 1008

[Sciencerocks]

wow, this isn't kidding. This may get named before 92L based on the circulation and convection blowing up over it!

[NXStumpy_Robothing]

Now 30/30.

2. A well-defined, non-tropical low pressure system is located about
100 miles southeast of Wilmington, North Carolina. Satellite and
radar data indicate that showers and thunderstorms have become a
little more concentrated near the center this morning. Furthermore,
recent satellite-derived wind data and surface observations indicate
that the circulation has become better defined, although the system
is still interacting with a frontal boundary. The low is forecast to
move northeastward for the next few days while passing over or near
the warm Gulf Stream today and Tuesday, which could allow for some
tropical development to occur while the system moves away from the
United States. The low should move over colder waters south of Nova
Scotia by early Wednesday, ending any opportunity for further
development.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...low...30 percent.

Forecaster Stewart

[Sciencerocks]

I'd have probably doubled those odds. IMO

[ElectricStorm]

Kinda came out of nowhere. Might steal Bill from 92L even.

[Subtrop]

Special tropical weather outlook issued to update the discussion of
the low-pressure system offshore the North Carolina coast.

Updated: A well-defined, non-tropical low pressure system is
located about 120 miles south of Cape Hatteras, North Carolina.
Satellite and radar data indicate that thunderstorm activity has
continued to increase and become more concentrated near the center
of the low early this morning, and environmental conditions are
expected to be at least marginally conducive for tropical cyclone
formation. If this recent development trend continues, then a
short-lived tropical depression or tropical storm could form later
today while the system moves northeastward away from the United
States. The low will move over colder waters south of Nova Scotia
on Wednesday, ending any opportunity for further development.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...50 percent.

[Hammy]

I think it warrants far higher than 50%. Too bad there's no site at Hatteras anymore.

[Shell Mound]

I think it warrants far higher than 50%. Too bad there's no site at Hatteras anymore.

https://i.imgur.com/1rYCTMN.gif

The vigorous MLC is a bit displaced from the LLC to its WSW, but storm-relative VWS is lessening due to favourable interaction with the trough, along with increasing divergence with height. 93L already looks to be very close to TS status, and will almost certainly become TS Bill within the next few hours. The latest shortwave imagery definitely indicates an increasingly organised system that is on the very cusp of TS-level intensity. The velocities on radar definitely support this. On the other hand, there are some potential issues in regard to classification:

 https://twitter.com/webberweather/status/1404380846274928644



 https://twitter.com/webberweather/status/1404382968995401733



 https://twitter.com/webberweather/status/1404384034772246537



 https://twitter.com/webberweather/status/1404385562778161154

[Aric Dunn]

We shall see.. would not take much more sustained convection to break whats left of that attachment.

The thing about the definition "attached" to a trough is ....that it does not say how far from the center.... essentially within its little "bubble" currently its almost certainly tropical. the attachment to the trough is well away from overall circ. if the outer fringe of the circ interacts with a trough does that magically stop it from being tropical .. no... the physics are still at play..

its only a definition.

[xironman]

The 3km NAM blew that up yesterday on the 06z run, but nothing else backed it up and the 12z did not develop it.

[Aric Dunn]

The 3km NAM blew that up yesterday on the 06z run, but nothing else backed it up and the 12z did not develop it.

Models miss things ALL THE TIME.

[Aric Dunn]

the last 30 min or so has seen what appears to the start of a proto inner core structure on radar..

they will likely have to pull the trigger on this one here shortly.

[aspen]

the last 30 min or so has seen what appears to the start of a proto inner core structure on radar..

they will likely have to pull the trigger on this one here shortly.

https://i.ibb.co/JnKw8q8/Capture.png

I’d say they increase the development odds to 70/70 and wait for 93L to sustain this look before they pull the trigger.

[Aric Dunn]

the last 30 min or so has seen what appears to the start of a proto inner core structure on radar..

they will likely have to pull the trigger on this one here shortly.

https://i.ibb.co/JnKw8q8/Capture.png

I’d say they increase the development odds to 70/70 and wait for 93L to sustain this look before they pull the trigger.

8 am it should go up for sure.

if they don't at 11am and it continues on this trend.. 5pm should be Bill.

[Aric Dunn]

Partial 'eyewall' structure starting to develop...

[Aric Dunn]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Mon Jun 14 2021

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Satellite, radar and surface observations indicate that a
well-defined low pressure system located about 90 miles southeast of
Cape Hatteras, North Carolina, is acquiring more tropical
characteristics. Environmental conditions appear conducive for
further development, and a tropical depression or tropical storm is
likely to form later today or tonight. This system is expected to
move northeastward away from the United States and move over colder
waters south of Nova Scotia on Wednesday, ending any opportunity for
further development by midweek.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...70 percent.

[MGC]

Gulf Stream working its magic, should be Bill later today.....MGC

[Aric Dunn]

The Trends continue pretty quickly right now..

probably will be bill at 11 am.

[Iceresistance]

Spotted a impressive rainband, & a lot of Lightning in there as well on Satellite.


On the Mobile version of S2K

[Nancy Smar]

TXNT26 KNES 141146
TCSNTL

A. TROPICAL DISTURBANCE (93L)

B. 14/1131Z

C. 34.5N

D. 74.5W

E. THREE/GOES-E

F. T1.0/1.0

G. IR/EIR/VIS

H. REMARKS...>2/10 BANDING AROUND LLCC YIELDS DT OF 1.0. MET AND PT
AGREE AND FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...MLEVINE