ATL: ROSE - Post-Tropical - Discussion

[Ubuntwo]

97L is still somewhat entangled in the monsoon trough (based on surface and vorticity analysis). May have prevented earlier designation, but the system is improving by the minute.

[zhukm29]

With the recent ASCAT pass on 95L and buoy data, we could be getting a rare double classification tonight...

With Olga/Pablo in 2019, Olga was already designated as 17L before Pablo was designated. This is probably the first time we could potentially see two invests become named storms at exactly the same time, meaning both the name and the storm number could be given out simultaneously. I can't think of any other time this has happened, especially given how hard it is for something like this to occur.

[Category5Kaiju]

With the recent ASCAT pass on 95L and buoy data, we could be getting a rare double classification tonight...

With Olga/Pablo in 2019, Olga was already designated as 17L before Pablo was designated. This is probably the first time we could potentially see two invests become named storms at exactly the same time, meaning both the name and the storm number could be given out simultaneously. I can't think of any other time this has happened, especially given how hard it is for something like this to occur.

If something like that happens, I wonder which will be which. Does the more eastern storm get the earlier lettered name?

[aspen]

The 12z HWRF has a favorable UL environment for 97L's last 12 hours or so over >26C SSTs before running into a wall of shear. Since it is likely already a TC, the HWRF probably has not initialized it well, so it could potentially get stronger. A Cat 1 is not impossible.



The continued convective burst should help 97L's developing LLC fully detach from the ITCZ/Monsoon trough.

[Hammy]

They (NHC) might make a special advisory for this one. Looks pretty good right now.

I doubt they would given it's nowhere near land and isn't rapidly intensifying but we'll probably get the 'if this trend continues' wording in an hour.

[aspen]

They (NHC) might make a special advisory for this one. Looks pretty good right now.

I doubt they would given it's nowhere near land and isn't rapidly intensifying but we'll probably get the 'if this trend continues' wording in an hour.

They did not go with that. Just up to 70/70 and saying a TD will form in the next day or two. We’ll probably need a really good ASCAT pass to upgrade this, even though it’s probably a TC already.

[Yellow Evan]

Showers and thunderstorms are also showing signs of organization in
association with a low pressure system located over the far eastern
Atlantic a few hundred miles south-southwest of the Cabo Verde
Islands. Environmental conditions appear conducive for further
development of this system, and a tropical depression is likely to
form during the next day or two while moving toward the northwest at
10 to 15 mph to the west of the Cabo Verde Islands. This system is
expected to reach cooler waters and an area of stronger upper-level
winds early next week, which should limit its development.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...70 percent.

[Yellow Evan]

TXNT23 KNES 190006
TCSNTL

A. TROPICAL DISTURBANCE (97L)

B. 18/2330Z

C. 9.5N

D. 27.0W

E. THREE/MET-11

F. T1.5/1.5

G. IR/EIR/SWIR

H. REMARKS...3/10 BANDING WAS OBSERVED AROUND THE LLCC WHICH RESULTS IN A
DT EQUAL TO 1.5. THE MET AND PT AGREE WITH THE DT. PERSISTENT CONVECTION
WAS OBSERVED TO THE WEST NEAR THE REGION OF THE LLCC. THE FT IS BASED
ON THE DT.

I. ADDL POSITIONS

NIL


...SAMBUCCI

[cycloneye]

 https://twitter.com/webberweather/status/1439387525236232198

[aspen]

The post-season best track will probably have the time of genesis revised to midday today. I’m still surprised the NHC has seemingly been lagging a bit behind with it.

[ouragans]

97L page is no longer accessible on RAMMB...

EDIT: and best track wind speed upped to 30 kts

Invest 97L
As of 00:00 UTC Sep 19, 2021:

Location: 10.5°N 27.3°W
Maximum Winds: 30 kt Gusts: N/A
Minimum Central Pressure: 1008 mb
Environmental Pressure: N/A
Radius of Circulation: N/A
Radius of Maximum wind: 70 nm

[Sciencerocks]

[Hammy]

https://twitter.com/webberweather/status/1439387525236232198

A bit off topic, but I could've sworn Webb worked at NHC.

[zhukm29]

I guess we'll have to wait until tomorrow for designation, kind of strange they still aren't classifying it. They're the experts though so they probably have a reason, but 97L has looked like a bona fide tropical cyclone for a while now, supported by ASCAT earlier as well. As a point of reference, here is Wilfred last year, in a pretty similar location with almost the exact same look, but it was classified much earlier.

 https://twitter.com/philklotzbach/status/1306966237335810049

[Sciencerocks]

[Sciencerocks]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Sun Sep 19 2021

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

The National Hurricane Center is issuing advisories on newly formed
Tropical Depression Sixteen, located a several hundred miles east of
the northern Leeward Island.

Recent satellite-derived wind data indicate that the small low
pressure system located over the far eastern tropical Atlantic a few
hundred miles south-southwest of the Cabo Verde Islands has become
better defined. Associated thunderstorm activity has also become
more concentrated near the center, and environmental conditions are
conducive for a tropical depression to form later this morning while
the low moves generally northwestward at 10 to 15 mph, well to the
west of the Cabo Verde Islands.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

[Subtrop]

AL, 17, 2021091906, , BEST, 0, 113N, 279W, 30, 1007, TD, 34, NEQ, 0, 0, 0, 0, 1012, 100, 30, 0, 0, L, 0, , 0, 0, SEVENTEEN, M, 0, , 0, 0, 0, 0, genesis-num, 036, TRANSITIONED, alC72021 to al172021,

[al78]

Is this the one that has now been classified as TD17? Looks like another year where many storms struggle in the MDR.

So many storms in the MDR over the last three years has been like this:
https://www.youtube.com/watch?v=oC_qLPJlGks

[LarryWx]

https://twitter.com/webberweather/status/1439387525236232198

A bit off topic, but I could've sworn Webb worked at NHC.

Mr. Webb actually lives in NM.

[aspen]

This looked better last night. While shear is low, there’s dry air all over the place that the NHC says will limit the system. Its current presentation suggests it has ingested some. Hopefully it’s able to mix it out and intensify because it’s not going to be impacting anyone.