ATL: FAY - Post-Tropical - Discussion

[GCANE]

Radar has it to the NE

[Aric Dunn]

Radar has it to the NE

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

https://imgur.com/6NhNrB3

Surface obs, radar and SAT are now starting to show the vorticity offshore charelston (we have been talking about all day) is started to become more defined. the lowest pressures are down there, the little bit of convection that is building now has pretty easily begun pulling in NE winds which is showing up on the surface obs.

would not be surprised if we see a decent burst of convection with that area. it has all the momentum.

[GCANE]

Radar has it to the NE

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

https://imgur.com/6NhNrB3

Surface obs, radar and SAT are now starting to show the vorticity offshore charelston (we have been talking about all day) is started to become more defined. the lowest pressures are down there, the little bit of convection that is building now has pretty easily begun pulling in NE winds which is showing up on the surface obs.

would not be surprised if we see a decent burst of convection with that area. it has all the momentum.

Still has a strong UL Jet over it.

[GCANE]

Watching the area with the deepest convection and highest helicity.
Theory is that the helicity would equalize the rotational momentum in all levels, aka stacking.

[aspen]

Center reformation is looking more likely

https://mobile.twitter.com/TropicalTidb ... 1404834821

[Aric Dunn]

Southern vorticity is taking all the energy.. once it rotates east/ene into the convection is when the magic will happen. Shear is lower south as well.

to the north the eddys that develop get spit out from the shear.

[NXStumpy_Robothing]

The system is seemingly wanting to consolidate east of Wilmington (as evidenced by the spin in low-level clouds), but the 20 knots of 200-850mb shear are ripping away convection. Could provide an opportunity for the more favorable southern environment to ramp up existing vorticity and spin in the area.

Ultimately, the environment is overall favorable (though less favorable the closer you get to the Outer Banks) - there just needs to be a vort that becomes dominant and allows the broad rotation to tighten up.

[GCANE]

Naked swirl alert
The UL Jet is doing a number on this.

[Aric Dunn]

Convection rapidly building on the southern portion as the vorticity approaches..

tilt of the trough is starting to shift to more NNW to SSE.

if the southern area takes off it will be well offshore for a lot longer.

[aspen]

Naked swirl alert
The UL Jet is doing a number on this.

https://i.imgur.com/T0LPe6Y.png

Maybe looks worthy of being called a Potential Tropical Cyclone.

[toad strangler]

Normally I would laugh at this Invest with great gusto. However, the propensity for these weak sauce systems so far in 2020 that WANT to develop regardless of negative immediate influences combined with much larger indicators abroad has me too concerned about peak season to laugh.

[Steve]

Normally I would laugh at this Invest with great gusto. However, the propensity for these weak sauce systems so far in 2020 that WANT to develop regardless of negative immediate influences combined with much larger indicators abroad has me too concerned about peak season to laugh.

Yeah. I was going to make a Beavis and Butthead joke to USTropics' "if you understand what a dict is", but I thought the better of it because I can't code and don't know calculus.

Looks like it's still in a brewing stage. I don't think shear is all /that/ strong, but you can see cloud tops being blown off west-east for several hundred miles and all the way back to Mississippi. You'd expect 98L to struggle a bit, but if a circulation can consolidate off the NC Coast or find its way there, we might see some intensification. I still don't think it will get above 55-60 (if that), but I'm pretty sure it will get named.


https://cdn.star.nesdis.noaa.gov//GOES1 ... 0x1000.gif

[NXStumpy_Robothing]

The current dominant eddy east of Wilmington is attempting to build, as it's been slowly gaining definition on radar. It does lack sustained convection for the most part, but many models are sticking with it to become the center of 98L for now.

Doing this despite the 20kts of shear is pretty impressive. Whether this continues and consolidates the vorticity (which is still quite broad, with evident vorticity as far south as Jacksonville) is the important thing to watch in the coming hours.

[aspen]

The models do favor it consolidating. Both the GFS and Euro have a tighter system, comparable to the ICON runs of the past few days (it still hasn’t backed off from a ~1000 mbar landfall on Saturday by a decently well organized TS).

[Aric Dunn]

The vorticity to the south has begun turning to the ene/NE.

this is when we should begin to see another vort max tighten up down there. but with less shear and moving with the shear. should give it a chance to consolidate the broad rotating as it swings to the north.

the vort to the north will weaken as it moves inland soon.

[Monsoonjr99]

The current dominant eddy east of Wilmington is attempting to build, as it's been slowly gaining definition on radar. It does lack sustained convection for the most part, but many models are sticking with it to become the center of 98L for now.

Doing this despite the 20kts of shear is pretty impressive. Whether this continues and consolidates the vorticity (which is still quite broad, with evident vorticity as far south as Jacksonville) is the important thing to watch in the coming hours.

I wonder why the models are so insistent on that northern vorticity in the higher shear becoming the dominant circulation. The convection to its east is now collapsing so a center relocation from that vortmax is seemingly less likely. Shear is lower and convection is currently more sustained further south, so why haven't any models keyed in on the southern vorticity? Is this due to baroclinic forcing helping the circulation to the north (hence why this may be subtropical)?

[cycloneye]

80%/80%

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Wed Jul 8 2020

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

An area of low pressure located about 60 miles east-southeast of
Wilmington, North Carolina, continues to produce a large area of
disorganized showers and thunderstorms over the adjacent Atlantic
waters and portions of eastern North Carolina. The low is expected
to move northeastward near or just offshore of the North Carolina
Outer Banks on Thursday, and then turn north-northeastward and move
along the mid-Atlantic coast on Friday. Environmental conditions
are expected to be conducive for development, and a tropical or
subtropical cyclone is likely to form within the next day or so.
Regardless of development, the system is expected to produce locally
heavy rainfall that could cause some flash flooding across portions
of eastern North Carolina, the coastal mid-Atlantic, and southern
New England during the next few days. Gusty winds are also possible
along the North Carolina Outer Banks through Thursday, and along
the mid-Atlantic and southern New England coasts Friday and
Saturday. Interests in these areas should monitor the progress of
this system and refer to products from your local National Weather
Service office.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...80 percent.

$$
Forecaster Stewart

[EquusStorm]

Looks to me like the only thing stopping this from getting named is land interaction, if it moves more north than east and keeps the center partly onshore. Of course if the center reforms to the south that would keep it a little further away

[Aric Dunn]

you can see the southern circ starting to take shape pretty clearly.. too bad the sun is setting and it is out of radar range now.

https://weather.cod.edu/satrad/?parms=s ... =undefined

[NXStumpy_Robothing]

The current dominant eddy east of Wilmington is attempting to build, as it's been slowly gaining definition on radar. It does lack sustained convection for the most part, but many models are sticking with it to become the center of 98L for now.

Doing this despite the 20kts of shear is pretty impressive. Whether this continues and consolidates the vorticity (which is still quite broad, with evident vorticity as far south as Jacksonville) is the important thing to watch in the coming hours.

I wonder why the models are so insistent on that northern vorticity in the higher shear becoming the dominant circulation. The convection to its east is now collapsing so a center relocation from that vortmax is seemingly less likely. Shear is lower and convection is currently more sustained further south, so why haven't any models keyed in on the southern vorticity? Is this due to baroclinic forcing helping the circulation to the north (hence why this may be subtropical)?

From my understanding of the dynamics that many models are attempting to display, they see the lower-level vorticity that stretches from the Outer Banks to Jacksonville as not having another area to consolidate around beyond the eddy east of Wilmington. They see the mid-level shear as being too much of an inhibiting factor for anything near the strongest convection to currently spin up. Right now, there's no evident spin beyond the previously-mentioned eddy (though one may be attempting to develop ESE of Charleston), and vorticity is not expected to consolidate to form a competing center. The Wilmington spin also features vorticity that is vertically stacked to about 500mb, which could allow it to survive despite the shear and land interaction. Whether that holds true or if we're in for a southern surprise is a question that has yet to be answered.

Also, I do not believe baroclinic forcing is acting on the system currently. That will be more of a factor once it begins to approach the Northeast. Sorry for the ramble.