NATL: IMELDA - Models

[shah83]

Looks like the slowdown on 12z GFS (compared to its own runs earlier) makes things even more problematic, as it (1) gives 94L more time to strengthen before landfall, and (2) allows for a more explicit stall due to shorter distance to Humberto, while maintaining higher intensity and thus rainfall potential during the stall.

Yeah, you're right. 12z GFZ essentially replicates the 2015 SC flood situation with Hurricane Joaquin providing the moisture.

[tolakram]

12Z GFS

[Stratton23]

CMC is wonky, very complex pattern with ridging trying to trap/ stall out 94L

[LarryWx]

12Z:
CMC hits NC after the loop.

UKMET goes OTS again like the Icon

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 42 HOURS
FORECAST POSITION AT T+ 42 : 23.3N 76.7W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 28.09.2025 48 24.2N 76.7W 1007 33
0000UTC 29.09.2025 60 25.2N 77.4W 1004 34
1200UTC 29.09.2025 72 26.7N 77.8W 1003 38
0000UTC 30.09.2025 84 28.2N 77.6W 1001 36
1200UTC 30.09.2025 96 28.9N 78.5W 996 42
0000UTC 01.10.2025 108 28.7N 77.8W 994 40
1200UTC 01.10.2025 120 28.5N 76.6W 992 38
0000UTC 02.10.2025 132 28.7N 74.3W 991 46
1200UTC 02.10.2025 144 28.9N 72.2W 991 54
0000UTC 03.10.2025 156 28.7N 69.6W 992 63
1200UTC 03.10.2025 168 28.6N 68.4W 995 52

[BobHarlem]

12z cmc delayed landfall

[MEANINGLESS_NUMBERS]

12z cmc delayed landfall

https://i.postimg.cc/Qdy5XjVM/floop-gdps-2025092612-sfcwind-mslp-swatl-2.gif

That’s 24 inches of rain in Wilmington, NC.

GFS has 24++ on Atlanta though so idk which is worse.

[LarryWx]

12Z Euro gets close to CHS, but does it then stall? I’m not sure.

[tolakram]

12Z Euro


source: https://www.pivotalweather.com/model.php?m=ecmwf_full&p=prateptype_cat_ecmwf-imp&rh=2025092612&fh=90&r=us_se&dpdt=&mc=

[SFLcane]

New hafs gets fairly close to the florida eastcoast. One of those times to stress a tc is not a dot on a map the affects always extend far out from any given center. The cone only covers were the center is going to be.

Could potential bring squally rainbands onshore depending how close it gets.

[shah83]

dynamic models showing stalls

[Travorum]

12z Euro drops 20+ inches along most of the coast of the Carolinas including a monstrous 27.5 inches on Charleston.

[chaser1]

I don't really follow the ATL basin that much but I'm interested in the cases of classic Fujiwara effect between two hurricanes in this part of the world. The examples that I often see are those from the Western Pacific, but with future Imelda and Humberto there is a chance of having one for the Atlantic. Although the latest model runs do not show the "dancing TCs" scenario, yet.

Welcome! Come for the fujiwhara; stay for the drinks lol.
Let me ask you.... considering your particular interest and focus on tropical cyclone fujiwhara events (primarily from other basins), do you find that one particular model seems to excel in terms of better forecasting their interaction?

[wzrgirl1]

New hafs gets fairly close to the florida eastcoast. One of those times to stress a tc is not a dot on a map the affects always extend far out from any given center. The cone only covers were the center is going to be.

Potential squally rainbands..

https://i.postimg.cc/y8rth3pk/vvvvvvll.png

https://i.postimg.cc/gjDBxx62/ccc.png

That has been my concern is a stall and the ridge building back in forcing the storm west before it makes the north trajectory.

[boca]

New hafs gets fairly close to the florida eastcoast. One of those times to stress a tc is not a dot on a map the affects always extend far out from any given center. The cone only covers were the center is going to be.

Potential squally rainbands..

https://i.postimg.cc/y8rth3pk/vvvvvvll.png

https://i.postimg.cc/gjDBxx62/ccc.png

That has been my concern is a stall and the ridge building back in forcing the storm west before it makes the north trajectory.

The cold front advancing thru N Florida so hopefully that will maybe deflect it away.

[Blown Away]

AL, 94, 2025092618, , BEST, 0, 207N, 744W, 30, 1008, DB

GFS has been persistent with that 18-24 position run after run and it initializes near the 18z position then jumps NE??

[CycloysisNegative]

https://i.postimg.cc/v813V8p8/gfs-mslp- ... fh6-24.gif

AL, 94, 2025092618, , BEST, 0, 207N, 744W, 30, 1008, DB

GFS has been persistent with that 18-24 position run after run and it initializes near the 18z position then jumps NE??

That’s probably an artifact of the algorithm used by TT (or any site for that matter). I’ve been building my own application that grabs the GFS data and plots it.

For displaying the “L” and the pressure, he has it coded somewhere to display it under some circumstance (e.g., If mslp < 1010mb), to avoid a bunch of them popping up all over it likely also sets a boundary, something like display the lowest pressure under a certain threshold in a 100mi radius (made up those numbers but you get the idea).

So it’s not that the system jumps, or that the GFS is doing something wonky, it’s that the area to the NE becomes the dominant mslp/vorticity position in that “boundary”. Hence the L disappears and reappears to the NE.


The GFS and any other model just provides the raw numbers, it’s up to a programmer on how to display it.

[Blown Away]

[url]https://i.postimg.cc/v813V8p8/gfs-mslp-pcpn-watl-fh6-24.gif [/url]

AL, 94, 2025092618, , BEST, 0, 207N, 744W, 30, 1008, DB

GFS has been persistent with that 18-24 position run after run and it initializes near the 18z position then jumps NE??

That’s probably an artifact of the algorithm used by TT (or any site for that matter). I’ve been building my own application that grabs the GFS data and plots it.

For displaying the “L” and the pressure, he has it coded somewhere to display it under some circumstance (e.g., If mslp < 1010mb), to avoid a bunch of them popping up all over it likely also sets a boundary, something like display the lowest pressure under a certain threshold in a 100mi radius (made up those numbers but you get the idea).

So it’s not that the system jumps, or that the GFS is doing something wonky, it’s that the area to the NE becomes the dominant mslp/vorticity position in that “boundary”. Hence the L disappears and reappears to the NE.


The GFS and any other model just provides the raw numbers, it’s up to a programmer on how to display it.

Wow, thank you for this great summary!

[ScottNAtlanta]

12z cmc delayed landfall

https://i.postimg.cc/Qdy5XjVM/floop-gdps-2025092612-sfcwind-mslp-swatl-2.gif

That’s 24 inches of rain in Wilmington, NC.

GFS has 24++ on Atlanta though so idk which is worse.

Where did you see 24 ++ in Atlanta??? I think that was 2.4

[ScottNAtlanta]

I think the gist of the track is that if 94L has a higher latitude than Humberto, your odds of a landfall are relatively high. If it is at a lower latitude, those odds go down quite a bit, but a landfall is still possible. Every scenario I've seem in the models with the first scenario landfall

[cycloneye]

Important part of the 5 PM discussion regarding the models.

It should be emphasized that the long-range intensity forecast depends
largely on where the system is and the degree of land interaction at those
periods, and therefore, is of low confidence. Given the higher-than-usual
uncertainty in the forecast track and intensity of the system, NOAA Hurricane
Hunter aircraft have been collecting data over the western Atlantic since
yesterday, and additional upper-air launches are occurring. This data collection
will continue through the weekend to help improve the model guidance for this
system.