ATL: ISAIAS - Post-Tropical - Discussion

[Do_For_Love]

The storm still seems to be moving pretty much W to me on the IR, when is it supposed to start getting a N motion? I guess today if it starts circulating it's western lobe? Some models had this thing going north of PR, I thought.

[USTropics]

No confirmation on an LLC looks like the only thing holding them back from going right to TS:

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Tue Jul 28 2020

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

1. An elongated area of low pressure located about 500 miles east of
the Windward Islands is producing a wide area of showers and
thunderstorms. Although recent satellite imagery suggests that the
system does not yet have a well-defined center, data from NOAA buoy
41040 indicate that the system is producing winds near
tropical-storm-force. An Air Force Reserve Hurricane Hunter aircraft
is scheduled to investigate the system this afternoon and will
provide more information about the current state of the disturbance.

Environmental conditions are expected to be conducive for additional
development and a tropical depression or tropical storm is likely to
form during the next couple of days while the system moves
west-northwestward at 15 to 20 mph and approaches the Leeward
Islands. Regardless of development, locally heavy rain is likely
across portions of the Lesser Antilles beginning later today and
continuing through Wednesday, especially in the Leeward Islands.
These conditions will spread westward to the Virgin Islands and
Puerto Rico Wednesday night and Thursday. Interests on these islands
should continue to monitor the progress of this system and tropical
storm watches or warnings could be required for portions of the area
later today.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...90 percent.

Forecaster Zelinsky

[Weatherboy1]

Latest TWO strongly suggests to me they're on the cusp of designating this … and when they do, it could jump right to TS vs. TD. So, we're going to go straight to watches/warnings IF it does consolidate its LLC. And given the fast motion and fast projected motion, we could have the 5-day cone enveloping part of Florida right off the bat - or be very, very close to that. Going to be interesting to see what happens today.

[Shell Mound]

If the southwestern lobe manages to become dominant, then the weaker, northeastern lobe, combined with the TUTT, could drag 92L/Isaias a bit farther north as it nears the northeastern Caribbean, especially if current trends continue and the SW lobe manages to consolidate faster within the next day or so. As angular momentum transfers to the southwestern lobe, the weakening, northeastern lobe rotates counterclockwise around the dominant lobe, while the circulation (wave axis) begins to align at the middle and upper levels. As the deepening system interacts with the TUTT near the islands, the dominant, southern lobe will still be drawn northward, then begin to push the TUTT away by days three through five, given an early start on development within the next twenty-four to thirty-six hours. So 92L/Isaias could still manage to avoid the larger islands of the Greater Antilles and instead interact with Puerto Rico and the Leewards at most (prior to the Bahamas, of course). Given current trends toward a slower, deeper shortwave trough over the southern Plains, a stronger 92L/Isaias could reinforce the stronger ridging to its north via diabetic outflow, which also serves to weaken the nearby TUTT, primarily by days three through five. This would imply a greater threat to FL/GA and perhaps the extreme eastern Gulf of Mexico. Current trends on satellite definitely suggest imminent development, with widespread deep convection persisting through the early diurnal minimum. For once the GFS-Parallel and the HWRF may be onto something.

Another important factor to consider: given the trend toward a more amplified NHEM pattern over the next three to five days, if 92L/Isaias manages to complete its current organisational cycle, (convectively) consolidate in the vicinity of its SW lobe, and intensify over the next day and a half, then the currently “unfavourable” environment north of the islands and near the Bahamas could rapidly become conducive to intensification. If a stronger 92L/Isaias in the short term would be better able to fend off the TUTT, especially given its sprawling circulation, then it could find itself in a very favourable environment as it nears the Southeastern U.S., especially FL/GA: as the TUTT splits, the trend toward a deeper, slower shortwave over the southern Plains will also favour UL divergence/anticyclonic flow over/near the Bahamas, in the vicinity of near-record TCHP. As we saw with Hanna, perhaps 92L/Isaias could then intensify much more than expected within a day or two of impacting the Southeastern U.S.—on short notice and with little prior indication from global models. This should be watched very closely.

[SouthDadeFish]

I don't understand why NHC isn't issuing advisories for a Potential Tropical Cyclone. The Antilles are within range of watches/warnings. My guess is the NHC is waiting until they feel more confident where a center will consolidate. Possibly after the recon flight today, if recon doesn't find a TC already.

[Aric Dunn]

I don't understand why NHC isn't issuing advisories for a Potential Tropical Cyclone. The Antilles are within range of watches/warnings. My guess is the NHC is waiting until they feel more confident where a center will consolidate. Possibly after the recon flight today, if recon doesn't find a TC already.

I was wondering the same thing...

except what about Barbados ... if they wait for Recon... Barbados will already be getting into the think of things..

[Emmett_Brown]

That TUTT is not very strong and it's retrograding W at a similar speed as 92L, so it could enhance outflow instead of shearing the system. Land interaction is the main inhibitor.

[RT23]

I don't understand why NHC isn't issuing advisories for a Potential Tropical Cyclone. The Antilles are within range of watches/warnings. My guess is the NHC is waiting until they feel more confident where a center will consolidate. Possibly after the recon flight today, if recon doesn't find a TC already.

I am also concerned that they have not, the proximity to the islands shouldve prompted at least TS watches at this time. The sys looks to be consolidated in the west more than the east this am and maybe i am wrong but there appeared to be a slight sw movement earlier.

[AutoPenalti]

I don't understand why NHC isn't issuing advisories for a Potential Tropical Cyclone. The Antilles are within range of watches/warnings. My guess is the NHC is waiting until they feel more confident where a center will consolidate. Possibly after the recon flight today, if recon doesn't find a TC already.

I am also concerned that they have not, the proximity to the islands shouldve prompted at least TS watches at this time. The sys looks to be consolidated in the west more than the east this am and maybe i am wrong but there appeared to be a slight sw movement earlier.

They’re waiting on recon most likely.

[GCANE]

GFS is trending more and more for this to get whacked in the Bahamas from an UL Jet.
The remnant wave below it, in the Carib, will track into an area of high UL Divergence, possibly a developing anticyclone.
I am a little surprised no one brought up the idea of a decouple yet.

[Weatherwatcher2018]

Currently getting showers in Barbados all morning so far

[supercane4867]

[northjaxpro]

I don't understand why NHC isn't issuing advisories for a Potential Tropical Cyclone. The Antilles are within range of watches/warnings. My guess is the NHC is waiting until they feel more confident where a center will consolidate. Possibly after the recon flight today, if recon doesn't find a TC already.

I am also concerned that they have not, the proximity to the islands shouldve prompted at least TS watches at this time. The sys looks to be consolidated in the west more than the east this am and maybe i am wrong but there appeared to be a slight sw movement earlier.

Reading the very latest TWO, they are on the cusp of classifying this as TS Isaisas this morning. They are awaiting Recon. We definitely will see some designation action today one way or another from NHC

[Shell Mound]

https://i.imgur.com/pA8R0fR.gif

Didn’t the precursors to Wilma ‘05, Matthew ‘16, and/or Dorian ‘18 also feature sprawling, monsoonal circulations interacting with an AEW?

Also, I’m starting to see signs of a convergent band on the northern side that is “linking up” with the deeper convection nearer the SW lobe.

[cycloneye]

A. TROPICAL DISTURBANCE (92L)

B. 28/1130Z

C. 14.6N

D. 49.9W

E. THREE/GOES-E

F. T1.0/1.0

G. IR/EIR/VIS

H. REMARKS...DUE TO RECENT RE-DEVELOPMENT, >2/10 BANDING WAS MEASURED
AROUND THE LLCC, RESULTING IN A DT OF 1.0. THE MET AND PT AGREE AND THE
FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...MLEVINE

[SouthDadeFish]

A. TROPICAL DISTURBANCE (92L)

B. 28/1130Z

C. 14.6N

D. 49.9W

E. THREE/GOES-E

F. T1.0/1.0

G. IR/EIR/VIS

H. REMARKS...DUE TO RECENT RE-DEVELOPMENT, >2/10 BANDING WAS MEASURED
AROUND THE LLCC, RESULTING IN A DT OF 1.0. THE MET AND PT AGREE AND THE
FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...MLEVINE

They went with the... eastern vort max...?

Interesting...

[msbee]

Well at least we know moisture wont be a problem.. lol

And honestly, it does not matter where the LLC finally consolidates..

it wont miss the islands.

No, unfortunately it won't miss the islands. I have never however seen so much uncertainty from the models.
I am planning here on St Maarten for at least tropical storm conditions. My worry is that others here might not be following so closely. If it doesn't have a name, its often not taken seriously. I have seen how much flooding can occur from these systems though, so I am not taking anything lightly.

[RT23]

A. TROPICAL DISTURBANCE (92L)

B. 28/1130Z

C. 14.6N

D. 49.9W

E. THREE/GOES-E

F. T1.0/1.0

G. IR/EIR/VIS

H. REMARKS...DUE TO RECENT RE-DEVELOPMENT, >2/10 BANDING WAS MEASURED
AROUND THE LLCC, RESULTING IN A DT OF 1.0. THE MET AND PT AGREE AND THE
FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...MLEVINE

They went with the... eastern vort max...?

Interesting...

I am in awe as well, the western vort seems more conducive to more defined to be the LLC.

[Aric Dunn]

A. TROPICAL DISTURBANCE (92L)

B. 28/1130Z

C. 14.6N

D. 49.9W

E. THREE/GOES-E

F. T1.0/1.0

G. IR/EIR/VIS

H. REMARKS...DUE TO RECENT RE-DEVELOPMENT, >2/10 BANDING WAS MEASURED
AROUND THE LLCC, RESULTING IN A DT OF 1.0. THE MET AND PT AGREE AND THE
FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...MLEVINE

They went with the... eastern vort max...?

Interesting...

I am in awe as well, the western vort seems more conducive to more defined to be the LLC.

Looks like they cut the difference..

Between the two lobes.

Nope nevermind.. they went with the eastern one..

Weird

[HurricaneAndre2008]

* GFS version *
* ATLANTIC 2020 SHIPS INTENSITY FORECAST *
* IR SAT DATA AVAILABLE, OHC AVAILABLE *
* INVEST AL922020 07/28/20 12 UTC *

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120 132 144 156 168
V (KT) NO LAND 35 39 44 47 51 56 61 70 68 66 64 65 64 66 67 73 73
V (KT) LAND 35 39 44 47