ATL: SAM - Remnants - Discussion

[cycloneye]

What was the trigger, an ASCAT pass?

[Subtrop]

SAM, AL, L, , , , , 18, 2021, TS, S, 2021091900, 9999999999, , 038, , , 1, WARNING, 3, AL182021

[Iceresistance]

What was the trigger, an ASCAT pass?

[Blown Away]

Sam is here, looking good and appears to have picked up forward speed.

[AutoPenalti]

What was the trigger, an ASCAT pass?

https://s9.gifyu.com/images/ascat_18L_speed_202109230141.png

https://s9.gifyu.com/images/ascat_18L_barb_202109230141.png

That's still elongated NW-SE...

[aspen]

What was the trigger, an ASCAT pass?

https://s9.gifyu.com/images/ascat_18L_speed_202109230141.png

https://s9.gifyu.com/images/ascat_18L_barb_202109230141.png

That's still elongated NW-SE...

It’s also over 10 hours old. The NHC must’ve gotten a more recent pass that isn’t public yet.

[Extratropical94]

What was the trigger, an ASCAT pass?

Dvorak maybe? Last two fixes from SAB came in at 3.5/3.5 and 3.0/3.5. TAFB is constant at 2.5/2.5. 40kts seems reasonable as a blend of estimates.

[AnnularCane]

It's going to be a pretty storm

He's already there.

[aspen]

Reposting this here from the models thread.

06z HWRF develops an anticyclone over Sam with outflow in all directions by Saturday morning, and it remains throughout the rest of the run.
https://i.imgur.com/Q1hOJUZ.png
https://i.imgur.com/EQ9N8W5.png
Warm SSTs (up to 29.5C depending on how far SW it gets), ample atmospheric moisture, and low shear all combined with this fantastic UL setup will allow for Sam to undergo RI once it has a well-structured inner core. My guess is that it'll reach Cat 4 intensity between late Saturday and early Sunday.

This UL setup will help Sam get close to the minimum possible pressures in its path. The most recent track has it cross through waters capable of supporting a moderate to high-end Cat 4 (940-925mb). Further south, and a Cat 5 is not out of the question. Hopefully it spares the islands like Jose.

[tolakram]

What was the trigger, an ASCAT pass?

Dvorak maybe? Last two fixes from SAB came in at 3.5/3.5 and 3.0/3.5. TAFB is constant at 2.5/2.5. 40kts seems reasonable as a blend of estimates.

I can't find any official confirmation this is Sam. Best Track is not official, the NHC can and has changed it in the past. Only the advisory, or a tweet from the NHC or a mention on their homepage is official.

[Extratropical94]

What was the trigger, an ASCAT pass?

Dvorak maybe? Last two fixes from SAB came in at 3.5/3.5 and 3.0/3.5. TAFB is constant at 2.5/2.5. 40kts seems reasonable as a blend of estimates.

I can't find any official confirmation this is Sam. Best Track is not official, the NHC can and has changed it in the past. Only the advisory, or a tweet from the NHC or a mention on their homepage is official.

True, it should be official in an hour or so when they release the advisory package.

[Iceresistance]

We need to wait until 10 AM CDT for Public Advisory #4, Special Advisory or update is given out from the NHC to confirm that TD 18 is TS Sam . . .

[zzh]

[Shell Mound]

https://i.imgur.com/Q8mZclP.gif
Sam is here, looking good and appears to have picked up forward speed.

The circulation still looks to be elongated and is not vertically stacked yet. The ASCAT pass at 11:47 UTC did not reveal winds higher than 30 kt. Satellite estimates, especially Dvorak, can be inaccurate, especially if a system is structurally sheared, as TD Eighteen still appears to be, owing to northeasterly mid-level shear. Given ongoing disorganisation, I think this system is still a 30-kt depression rather than a 40-kt TS. Within the next five days I think the NHC will be forced to gradually shift its track farther southwest and also show a weaker system (sub-MH) through 120h. I think the risk of a landfall on the Leeward Islands is increasing, but soon-to-be-Sam will probably be weaker than 100 kt at that time. I think Sam-to-be is likely to be on the order of 75–85 kt at the time of its closest approach to the northeastern Caribbean, as models have tended to overestimate short-term RI in the MDR and eastern Caribbean thus far.

[ColdMiser123]

Will likely have to deal with some dry air to the north in the short-term, you can see this quite well on the morning visible loop.

[zzh]

https://i.imgur.com/Q8mZclP.gif
Sam is here, looking good and appears to have picked up forward speed.

The circulation still looks to be elongated and is not vertically stacked yet. The ASCAT pass at 11:47 UTC did not reveal winds higher than 30 kt. Satellite estimates, especially Dvorak, can be inaccurate, especially if a system is structurally sheared, as TD Eighteen still appears to be, owing to northeasterly mid-level shear. Given ongoing disorganisation, I think this system is still a 30-kt depression rather than a 40-kt TS. Within the next five days I think the NHC will be forced to gradually shift its track farther southwest and also show a weaker system (sub-MH) through 120h. I think the risk of a landfall on the Leeward Islands is increasing, but soon-to-be-Sam will probably be weaker than 100 kt at that time. I think Sam-to-be is likely to be on the order of 75–85 kt at the time of its closest approach to the northeastern Caribbean, as models have tended to overestimate short-term RI in the MDR and eastern Caribbean thus far.

There are a lot of 35kt barbs on the north side....

[Shell Mound]

https://i.imgur.com/Q8mZclP.gif
Sam is here, looking good and appears to have picked up forward speed.

The circulation still looks to be elongated and is not vertically stacked yet. The ASCAT pass at 11:47 UTC did not reveal winds higher than 30 kt. Satellite estimates, especially Dvorak, can be inaccurate, especially if a system is structurally sheared, as TD Eighteen still appears to be, owing to northeasterly mid-level shear. Given ongoing disorganisation, I think this system is still a 30-kt depression rather than a 40-kt TS. Within the next five days I think the NHC will be forced to gradually shift its track farther southwest and also show a weaker system (sub-MH) through 120h. I think the risk of a landfall on the Leeward Islands is increasing, but soon-to-be-Sam will probably be weaker than 100 kt at that time. I think Sam-to-be is likely to be on the order of 75–85 kt at the time of its closest approach to the northeastern Caribbean, as models have tended to overestimate short-term RI in the MDR and eastern Caribbean thus far.

There are a lot of 35kt barbs on the north side...

Ah, I did not see those brown barbs. Thank you for pointing them out! Regardless, EPS ensembles are now much weaker and farther SW through D5.

At least “Sam-I-am” is unlikely to resemble the Son of Sam, if models are to be trusted...

[Ubuntwo]

New ASCAT pass came in (12z) with a well-defined surface circ and 40kt winds on the north side. The system appears to be vertically stacked now. We should have Sam shortly.

[zzh]

[Iceresistance]

TD 18 is near 29°C SST, if the system moves further west & won't recurve, then look out . . .

The SSTs in the Caribbean are 29-30°C & is very favorable for Tropical Cyclones . . .