ATL: SAM - Remnants - Discussion

[gatorcane]

Imagine if Sam had formed about 3-4 weeks ago. Might have been more of a threat but thankfully Atlantic Cape Verde season is picking up long after the climo peak when recurves and fish are more likely.

[Hypercane_Kyle]

 https://twitter.com/AndyHazelton/status/1441377530557071380

[Teban54]

 https://twitter.com/AndyHazelton/status/1441381674072215553

[cycloneye]

AL, 18, 2021092412, , BEST, 0, 116N, 431W, 65, 993, HU

[aspen]

https://twitter.com/AndyHazelton/status/1441381674072215553?s=19

The outer band is weakening and the CDO now has the deepest convection, so we should see that competition end and the core trying to organize better.

[ElectricStorm]

New towers firing near the center. With the northern band fading away, it should be time to explode for Sam

[GCANE]

Checking GFS run-to run, 138 hrs out.
The forecast for the Rossby wave is all over the place.
No way to tell at this point if this really goes OTS or takes aim for New England.

[GCANE]

One feature GFS has been developing in the runs is this UL cutoff low off the Carolina's coast.
Could create a Fujiwhara effect and slingshot this bad boy into the coast.
NJ to NE needs to watch this closely.

[kevin]

Looks like Sam conquered its rebellious northern band. New convection is now firing near the center.

[ScottNAtlanta]

The ongoing spate of (E)RI will almost certainly contribute to eastward shifts in the guidance and allow Sam to miss the Leeward Islands, however narrowly. The strongest EPS and GEFS members have consistently taken Sam to the northeast of the Islands. Given that Sam is intensifying even more rapidly than either these or the intensity guidance indicated, the likelihood of an OTS trajectory increases tremendously. Ridging is not expected to be particularly strong, hence’s Sam relatively slow forward speed through D5. The only factor that will prevent Category-5 status at this point is the marginal thermodynamic environment, but otherwise all other indicators favour yet another powerful annular MH in D3–5. Expect Sam to be a stronger version of Larry.

I don't think that it is certain at all this is going out. The speed at which it is traveling is much more of an issue than how strong it is. If its a 70kt storm or a 120kt storm it is still going to follow the same steering. I think we need to pay very close attention as to whether this is hitting track forecast points and if it is off...which direction

They would not have the same steering, .

Any 70kt hurricane is going to extend into the upper levels and that's going to be where the steering comes from same as a 120kt one. I was quite deliberate with my wording. While a stronger hurricane can affect its environment more, if there is upper level NW flow, they are both going to feel it and respond accordingly.

[Sciencerocks]

[skyline385]

Well there's the big feeder band gone and convection is picking up through the center again, guess it's ready for some RI

[InfernoFlameCat]

That feeder band was like an umbilical cord wrapped around a baby. It was choking the system more than feeding it imo.

[Iceresistance]

Same Intensity as Previous Advisory

..SAM TAKING A MOMENTARY PAUSE IN STRENGTHENING... ...RAPID INTENSIFICATION FORECAST TO RESUME SOON...

11:00 AM AST Fri Sep 24
Location: 11.8°N 43.7°W
Moving: W at 14 mph
Min pressure: 993 mb
Max sustained: 75 mph

[WiscoWx02]

I do believe that feeder band from earlier was a response to dry air lurking just to the north of Sam. I remember reading that dry air near tropical systems promotes that band to their north like we have been seeing. Not at all surprised Sam didn't take off last night, didn't think it would, too small of a core. As others have mentioned, the feeder band to the north is dying off and convection has started to fire near the extremely small core again. Will probably be another 12 or + hours or so before Sam takes off in my opinion because the core is still too small to see much explosive intensification. After sunset though....latent heat will work its magic.

[kevin]

This is behaving exactly like how HWRF and HMON said it would. Yes those 2 models often overdo the long-term intensity of storms, especially of disturbances before they have formed into storms. But in terms of short term behaviour and structure I think they're probably the best models to use. Both of them kept Sam at the same intensity (990 - 996 mb and 65 kt) for the last few hours and only start RI around 21z, which is in about 6 hours. In the GIF below you can even see the shedding of Sam's northern band on HMON in almost the exact same way as what is actually happening right now. Would be interesting to know whether my hunch about HWRF/HMON performing very well with short-term structure has ever been quantatively shown in any research regarding hurricane models.

Looking beyond the next 6 hours of so, we should have a 969mb/82kt cat 1 (HWRF) or a 971mb/88kt cat 2 (HMON) this time tomorrow if HWRF/HMON are also correct about that slightly longer time range.

[ElectricStorm]

I do believe that feeder band from earlier was a response to dry air lurking just to the north of Sam. I remember reading that dry air near tropical systems promotes that band to their north like we have been seeing. Not at all surprised Sam didn't take off last night, didn't think it would, too small of a core. As others have mentioned, the feeder band to the north is dying off and convection has started to fire near the extremely small core again. Will probably be another 12 or + hours or so before Sam takes off in my opinion because the core is still too small to see much explosive intensification. After sunset though....latent heat will work its magic.

I don't really think the size of the core had much to with it as small cores can get going much quicker than large ones. I think the big band definitely hurt but now that its gone there shouldn't be much holding it back. If the core is small is could RI faster.

[galaxy401]

Sam looks to be already restrengthening after that pause now that the northern band is weaker.

[aspen]

Sam looks far better now that the feeder band has weakened and isn't competing with the center. The developing CDO should help close off the recently opened eyewall.

[skyline385]

Looking real good on IR now, forming that classical MDR storm structure