ATL: DEBBY - Post-Tropical - Discussion

[chaser1]

Could the models shift back east with this possible rotation being NE of the consensus center?

Models will change based on consistently updated and changing initialization which until clear cut, means timing issues with regard to current and downstream trough and ridge positions. Nothing is really clear right not until we have a more coherent vertical system.

[chaser1]

TD4 is one of those slow burn development processes; if this storm was in open ocean, they might not have declared it a depression just yet, since the center is clearly still in the formation stages. A fast moving band of showers passed by me in Sarasota an hour or so ago. It had some lightning, and a very chilly (relatively speaking) downdraft. So there is still is a lot of dry air aloft.

Am guessing that dry air is partially capping the LLC from becoming aligned with the broader mid level circulation. Then the low level easterlies simply push the LLC along. It seems that the mid level core is in somewhat of a COL, but certainly not moving with a NW forward motion that the low levels appear to be. So, perhaps the dry air IS further mitigating the process but I can't help but think that continued explosive convection to the south might try and induce a new LLC between Cuba and Isle of Youth? That or.... the entire gyre does finally gets nudged into the SE GOM and slow development finally begins but I don't see that occurring at the moment.

Emmett, to what extent do you think this will impact timing with the break/refilling of the ridge?

[Craters]

This could be why it is having problems...lots of low level dry air

https://i.imgur.com/1e3JmLO.gif

YES!!!!! (Or at least that's what I think.) Thanks for posting this, Scott. This view and the mid-level water-vapor loop (https://weather.cod.edu/satrad/?parms=meso-meso2-09-24-1-100-1&checked=map&colorbar=undefined) are very reminiscent of what it was like around Beryl in the day or so before landfall last month. Just about everything else was coming together, but the dry air was inhibiting enough to keep Beryl from really taking off. Hardly anybody was talking about it, though.

I don't know why, but it's a rare post here that talks about dry air. Personally, I think that it should get more respect, but that's just amateur me.

[Steve]

Banding (inflow I think) is blossoming west of the overall broad center. This has to happen during the slow consolidation. Watch for a pulse up early afternoon and then some of it dying off to reform during DMAX. I think it will tighten closer to landfall but it’s liable to be a strung out tropical storm with lots of breaks in the banding unlike a filled in hurricane. Main threats are training bands north and northeast of the center and possible tornadoes. I haven’t looked at the helicity but always a chance of some strays in those leader bands.

https://www.tropicaltidbits.com/sat/sat ... t=vis_swir

[Emmett_Brown]

TD4 is one of those slow burn development processes; if this storm was in open ocean, they might not have declared it a depression just yet, since the center is clearly still in the formation stages. A fast moving band of showers passed by me in Sarasota an hour or so ago. It had some lightning, and a very chilly (relatively speaking) downdraft. So there is still is a lot of dry air aloft.

Am guessing that dry air is partially capping the LLC from becoming aligned with the broader mid level circulation. Then the low level easterlies simply push the LLC along. It seems that the mid level core is in somewhat of a COL, but certainly not moving with a NW forward motion that the low levels appear to be. So, perhaps the dry air IS further mitigating the process but I can't help but think that continued explosive convection to the south might try and induce a new LLC between Cuba and Isle of Youth? That or.... the entire gyre does finally gets nudged into the SE GOM and slow development finally begins but I don't see that occurring at the moment.

Emmett, to what extent do you think this will impact timing with the break/refilling of the ridge?

Good question! My purely amateur view of this, is that the storm could easily stall in a day or 2 as the trough pulls away... because my gut tells me TD4 seems to be slowing down slightly, and storms typically slow a bit as they stack. The trough is so weak and progressive. I'm getting Elena vibes again.

[ScottNAtlanta]

There is a blowup right on top of the northern LLC, so lets see if that can expand. I think that center is the main one at this point, but its got lots of disjointed convective areas that are currently competing with one another.

[BIFF_THE_UNRULY]

getting some great rain in hudson florida right now. not sure if related

[hurricaneCW]

This could be why it is having problems...lots of low level dry air

https://i.imgur.com/1e3JmLO.gif

YES!!!!! (Or at least that's what I think.) Thanks for posting this, Scott. This view and the mid-level water-vapor loop (https://weather.cod.edu/satrad/?parms=meso-meso2-09-24-1-100-1&checked=map&colorbar=undefined) are very reminiscent of what it was like around Beryl in the day or so before landfall last month. Just about everything else was coming together, but the dry air was inhibiting enough to keep Beryl from really taking off. Hardly anybody was talking about it, though.

I don't know why, but it's a rare post here that talks about dry air. Personally, I think that it should get more respect, but that's just amateur me.

Dry air isn't a hindrance in a very low shear environment. Beryl had shear along with dry air entrainment which prevented organization

[robbielyn]

Levi talked about the dry air yesterday but i didn’t hear it from other mets or the nhc. Does anyone look at the current atmosphere in their forecasting or just mostly models? Kudos to Levi. I trust him the most he should be running the NHC in my opinion although i’m sure that would bore him to death. And no i’m not bashing nhc i trust them but i trust levi more.

[Jr0d]

Wind has calmed a bit in Key West, sun has been out most of the day. Most of the bands have missed the Key West area, Big Pine had a nasty one not long ago.

As I posted earlier, the squalls have brought gusty winds, 45 mph is the highest I have seen but I suspect the Big Pine area may have had higher gusts.

We are now under a tropical storm warning as of the 2pm update, I suppose the observations prompted this and we likely will more concentrated and stronger bands later today and overnight, even as the system pulls away from the area.

While so far our impact has been fairly tame, the potential for flooding is a major concern. I really do not know how much one can prepare if they are in area that sees so much rain, sand bags can only do so much.

Hopefully North and Central Florida, South Georgia, and other areas that might see serious flooding are taking precautions like putting valuables in high spots and having a plan to move their car(s) to a high point.

After getting flooded by Ian, I regretted not putting enough things high enough but was fortunate to have moved the cars out of harms way. Picking up the pieces in a flooded house is one of the toughest things emotionally I have dealt with.

[robbielyn]

Wind has calmed a bit in Key West, sun has been out most of the day. Most of the bands have missed the Key West area, Big Pine had a nasty one not long ago.

As I posted earlier, the squalls have brought gusty winds, 45 mph is the highest I have seen but I suspect the Big Pine area may have had higher gusts.

We are now under a tropical storm warning as of the 2pm update, I suppose the observations prompted this and we likely will more concentrated and stronger bands later today and overnight, even as the system pulls away from the area.

While so far our impact has been fairly tame, the potential for flooding is a major concern. I really do not know how much one can prepare if they are in area that sees so much rain, sand bags can only do so much.

Hopefully North and Central Florida, South Georgia, and other areas that might see serious flooding are taking precautions like putting valuables in high spots and having a plan to move their car(s) to a high point.

After getting flooded by Ian, I regretted not putting enough things high enough but was fortunate to have moved the cars out of harms way. Picking up the pieces in a flooded house is one of the toughest things emotionally I have dealt with.

Oh wow! I am sorry you had to go through that. i’m glad u r ok and your cars were spared.

[USTropics]

This could be why it is having problems...lots of low level dry air

https://i.imgur.com/1e3JmLO.gif

YES!!!!! (Or at least that's what I think.) Thanks for posting this, Scott. This view and the mid-level water-vapor loop (https://weather.cod.edu/satrad/?parms=meso-meso2-09-24-1-100-1&checked=map&colorbar=undefined) are very reminiscent of what it was like around Beryl in the day or so before landfall last month. Just about everything else was coming together, but the dry air was inhibiting enough to keep Beryl from really taking off. Hardly anybody was talking about it, though.

I don't know why, but it's a rare post here that talks about dry air. Personally, I think that it should get more respect, but that's just amateur me.

Dry air isn't a hindrance in a very low shear environment. Beryl had shear along with dry air entrainment which prevented organization

That low level WV product can be deceiving. RH values for the entire column are quite high ~90% with low shear (~5 kt). Dry air is present to the west but not currently an issue:


The broad nature of the circulation due to the wave envelope and interaction with Cuba are the main reasons for delayed consolidation and strengthening. Now that the LLC is off the coast, we should see some pulse phases this evening and early tomorrow morning to solidify the circulation and some deeper strengthening thereafter.

[stormhunter7]

MUHA 031750Z 12006KT 090V150 8000 FEW018TCU SCT020 BKN080 28/25 Q1009

Surface center appear to be west or NW of Havana?

https://weathercams.faa.gov/map/-82.681 ... ls/weather

[psyclone]

This thing needs a DMAX over water. That's going to happen tonight at which time substantial development is likely. The water in the eastern Gulf is dangerously warm. I'd expect a probable hurricane landfall somewhere within that hurricane watch area...but the main calling card for this system is most likely heavy rain and associated freshwater flooding which is the case for most of these systems. They're water storms. We talk wind and pressure, but water...in the form of heavy rain, storm surge and battering wave action does the dirty work much of the time.

[xironman]

That's one heck of a vort in a gyre.

[MGC]

Looks like TD4 has moved into the GOM this afternoon. Convection starting to pop near the center......MGC

[DunedinDave]

I’ve seen some ugly systems before. This is up there as one of the ugliest for sure.

[Jr0d]

Looks like TD4 has moved into the GOM this afternoon. Convection starting to pop near the center......MGC

If that convection persists until the 5pm update, I think it will make a strong case to justify an upgrade to Debby.

[stormhunter7]

Looks like TD4 has moved into the GOM this afternoon. Convection starting to pop near the center......MGC

If that convection persists until the 5pm update, I think it will make a strong case to justify an upgrade to Debby.

there is a lot of ships in the straight/area. Only gonna take one to report some winds for upgrade. https://www.ndbc.noaa.gov/radial_search.php?storm=at4

[Steve]

I’ve seen some ugly systems before. This is up there as one of the ugliest for sure.

Brewing

https://www.tropicaltidbits.com/sat/sat ... product=ir