ATL: EIGHT - Remnants - Discussion

[cycloneye]

AL, 95, 2024091500, , BEST, 0, 311N, 758W, 25, 1009, DB

https://ftp.nhc.noaa.gov/atcf/btk/bal952024.dat

[ROCK]

already looks like a LLC is trying to spin up tonight....

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sun Sep 15 2024

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

Active Systems:
The National Hurricane Center is issuing advisories on Tropical
Storm Gordon, located over the central tropical Atlantic Ocean.

Offshore the Southeastern U.S. Coast (AL95):
A non-tropical low pressure area is located along a frontal
boundary a couple of hundred miles off the southeastern U.S. coast,
and is producing winds to gale force north of its center. The low
is forecast to move northwestward or northward over the warm waters
of the Gulf Stream toward the coasts of North Carolina and South
Carolina, and it could become a subtropical or tropical storm during
the next day or two if the associated front dissipates and showers
and thunderstorms become sufficiently organized.

1. Regardless of tropical or subtropical development, the low is
likely to bring gusty winds, heavy rains with the potential for
flash flooding, coastal flooding, and dangerous beach conditions to
portions of the U.S. Southeast and Mid-Atlantic coast during the
next couple of days, and interests in these areas should monitor
the system's progress. Additional information can be found in
products issued by your local National Weather Service Forecast
Office and High Seas Forecasts issued by the National Weather
Service.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 7 days...medium...50 percent.

[shear_vector]

Not sure if this is the correct thread or perhaps a topic in talkin' tropics but my question is on subtrop/trop development froming off stalled fronts. Mods please split if this is the wrong place for this question. Thought this would be fun to discuss since we are about to see what will happen to this system in real-time the next 48 hours. So my question:

What are the tell-tale signs via satillite or surface obs that subtrop/trop development in proximity or being attached to a front? (ie: is it when via satillite data in can be determined that the LLC formed and becomes detached from the front(s) and the motion of the LLC acts\moves independently from the motion of the front, or the LLC begins to become more vertically stacked with a MLC, or via a more general frontal analysis of available observations of surface and upper atmosphehic data to determine if the front and any potential/active circulations are acting independently so the process of subtrop/trop development can become the dominate forcing mechanism from convective development as oppose to the front being the forcing mechinism for cenvective development.

I understand that perhaps the answer is a combination of a few things, but without using model data how is this determined via only using surface obs/satillite data.

Last question: where is the product that shows the four charts that are used to determine cold vs warm core development?

first time caller long time listener. interested to see what recon finds later today with this system!

-subtropical storm enthuisist in the carolinas

[Sciencerocks]

[wxman57]

already looks like a LLC is trying to spin up tonight....

The LLC clearly was present in ASCAT imagery last evening. It showed a 30kt closed low. Clearly non-tropical. It'll produce some 30-40 mph wind on the SC/NC beaches tomorrow prior to moving inland tomorrow evening. Those winds will not carry inland. NBM forecasts 3-4 inches of rain eastern NC and much of VA. That's about it.

[xironman]

Starting to spin up, the flight will be interesting

[ChrisH-UK]

This is GEOS-16 Concus GeoProxy with a merged lowest elevation radar overlayed and It might be getting there to been wrapped around.

Source - https://col.st/e2sjn

[TomballEd]

This is GEOS-16 Concus GeoProxy with a merged lowest elevation radar overlayed and It might be getting there to been wrapped around.

Source - https://col.st/e2sjn

[url]https://imagizer.imageshack.com/img922/2531/oyvsw4.gif [/url]

I've got a funny feeling just looking at low cloud motion that circulation radar sees in not at the surface. Although CIMMS 925 mb vort product sees an area of enhanced vorticity at the end of a more linear, frontal line of vorticity. Besides finding if that circulation is closed at the surface, seeing if there are dewpoint discontinuities or obvious frontal wind shifts will be interesting. Aircraft is on its way.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Sun Sep 15 2024

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

Active Systems:
The National Hurricane Center is issuing advisories on Tropical
Storm Gordon, located over the central tropical Atlantic Ocean.

Offshore the Southeastern U.S. Coast (AL95):
A non-tropical low pressure area is located along a frontal
boundary a couple of hundred miles off the southeastern U.S. coast,
and is producing winds to gale force north of its center. The low
is forecast to move northwestward or northward over the warm waters
of the Gulf Stream toward the coasts of North Carolina and South
Carolina, and it could become a subtropical or tropical storm during
the next day or so if the associated front dissipates and showers
and thunderstorms become sufficiently organized. An Air Force
Hurricane Hunter aircraft is currently investigating the system.

Regardless of tropical or subtropical development, the low is
likely to bring gusty winds, heavy rains with the potential for
flash flooding, coastal flooding, and dangerous beach conditions to
portions of the U.S. Southeast and Mid-Atlantic coast during the
next couple of days, and interests in these areas should monitor
the system's progress. Additional information can be found in
products issued by your local National Weather Service Forecast
Office and High Seas Forecasts issued by the National Weather
Service.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 7 days...medium...50 percent.

[xironman]

They missed left. If they do find tropical characteristics it would be straight to subtropical storm. 78 or a bit east of there

[kevin]

49 kt SFMR and 49 kt FL winds, sufficient for a current intensity of at least 45 kt. If recon manages to find a center it'd be a direct upgrade.

[underthwx]

They missed left. If they do find tropical characteristics it would be straight to subtropical storm. 78 or a bit east of there

https://i.imgur.com/KfPLRrW.gif

Sure does look as if it's trying....

[wxman57]

It's fairly clear that there has been a closed low with gale-force wind since last evening. I would think that if the NHC intended to issue advisories on this frontal low that they would have already started them yesterday. The center will be inland within 24 hours. Some 35-45 mph wind on the beaches tomorrow and that's about it. Weaker than a typical nor'easter. I'm hoping they just let it move ashore without advisories. However, I have an advisory ready to go.

[MarioProtVI]

It's fairly clear that there has been a closed low with gale-force wind since last evening. I would think that if the NHC intended to issue advisories on this frontal low that they would have already started them yesterday. The center will be inland within 24 hours. Some 35-45 mph wind on the beaches tomorrow and that's about it. Weaker than a typical nor'easter. I'm hoping they just let it move ashore without advisories. However, I have an advisory ready to go.

Well there was a wind shift and ~1007 extrap with around 40 kt support. Last year Ophelia was designated under similar conditions even if it was still dubious for a bit, so I think they probably wanted to wait until recon found some evidence of a closed circ before starting advisories.

Edit: as soon as I sent that NHC pulled the trigger for a POTC

[MarioProtVI]

 https://x.com/nhc_atlantic/status/1835410217334603844

[wxman57]

It's fairly clear that there has been a closed low with gale-force wind since last evening. I would think that if the NHC intended to issue advisories on this frontal low that they would have already started them yesterday. The center will be inland within 24 hours. Some 35-45 mph wind on the beaches tomorrow and that's about it. Weaker than a typical nor'easter. I'm hoping they just let it move ashore without advisories. However, I have an advisory ready to go.

Well there was a wind shift and ~1007 extrap with around 40 kt support. Last year Ophelia was designated under similar conditions even if it was still dubious for a bit, so I think they probably wanted to wait until recon found some evidence of a closed circ before starting advisories.

Edit: as soon as I sent that NHC pulled the trigger for a POTC

PTC means center is now well-defined enough to issue regular advisories. Only question is whether they go STS or TS.

[Sciencerocks]

[KPILM]

I'm in a CDL truck training evening class at CFCC here in Wilmington, and our first highway driving is supposed to be tomorrow evening, really hoping they call it off so my first real on the road training isn't taking place in sheets of rain and high winds

[cheezyWXguy]

Since radar is seeing in the mid levels, and I’m not sure how well stacked this system is, it’s hard to tell how much this translates to the low levels. However radar is looking quite interesting at the moment. Looks like an eyewall feature is developing. Velocities not especially impressive, only 45-55mph, but the circulation looks fairly tight.