NATL: GABRIELLE - Models

[LarryWx]

More 12Z runs:

The models have switched in some cases. The GFS/CMC moved W to just SE of Bermuda whereas the Euro moved E to well E of Bermuda.

Icon: still well to the SW of others with it much weaker SSW of Bermuda then recurving NW

JMA: TS at Bermuda at 192

[MEANINGLESS_NUMBERS]

A bit of a spread in the intensity forecasts…

[BobHarlem]

18z gfs is closer to bermuda, 18z icon shifted right and aligns pretty closely with the 18z GFS out to the end of the icon's run.

[LarryWx]

0Z UKMET: passes pretty close to the E of Bermuda; it is significantly weaker than prior run with 1008 mb it’s strongest vs 998 on prior:

TROPICAL DEPRESSION 92L ANALYSED POSITION : 14.4N 43.9W

ATCF IDENTIFIER : AL922025

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
0000UTC 17.09.2025 0 14.4N 43.9W 1010 28
1200UTC 17.09.2025 12 16.9N 45.4W 1009 33
0000UTC 18.09.2025 24 19.5N 48.0W 1009 41
1200UTC 18.09.2025 36 20.7N 50.6W 1008 37
0000UTC 19.09.2025 48 21.3N 53.3W 1008 31
1200UTC 19.09.2025 60 21.7N 55.6W 1009 27
0000UTC 20.09.2025 72 22.0N 57.6W 1010 26
1200UTC 20.09.2025 84 23.3N 59.0W 1010 30
0000UTC 21.09.2025 96 24.8N 60.2W 1010 29
1200UTC 21.09.2025 108 26.2N 60.8W 1010 32
0000UTC 22.09.2025 120 27.5N 61.9W 1009 37
1200UTC 22.09.2025 132 29.2N 63.5W 1010 37
0000UTC 23.09.2025 144 31.1N 63.5W 1010 34
1200UTC 23.09.2025 156 33.1N 62.8W 1010 33
0000UTC 24.09.2025 168 34.0N 59.7W 1009 30

[LarryWx]

Check this out folks: 0Z GFS is much weaker with strongest at 1005 mb/barely a TS followed by it weakening and then dissipating over open water of the SW Atlantic into nothing! The prior 13 runs all had hurricanes, usually MH! What the?

[Pelicane]

Check this out folks: 0Z GFS is much weaker with strongest at 1005 mb/barely a TS followed by it weakening and then dissipating over open water of the SW Atlantic into nothing! The prior 13 runs all had hurricanes, usually MH! What the?

Would be a bad look for the models if this also vastly underperforms. Great news for real life impacts though.

[Kazmit]

Check this out folks: 0Z GFS is much weaker with strongest at 1005 mb/barely a TS followed by it weakening and then dissipating over open water of the SW Atlantic into nothing! The prior 13 runs all had hurricanes, usually MH! What the?

Would be a bad look for the models if this also vastly underperforms. Great news for real life impacts though.

Back to showing a MH now, after a stall in favorable conditions south of Bermuda. Weird.

[cycloneye]

[TampaWxLurker]

12z Icon keeps it weak in the mid-990's for pressure, faster than the prior runs and decently east of Bermuda. Doesn't seem to take off in strength until getting northeast of Bermuda.

[cycloneye]

Big downtrend on the 12z GFS.

[TampaWxLurker]

12z GFS seems to go 'poof' before getting to Bermuda by 144 hrs. Will see if it reforms later in the run.

Edit: GFS keeps it weak and essentially stalled for a few days SW of Bermuda. Finally starts to move to the north, west of Bermuda by +228 hrs, 999mb. So still as a tropical storm.

[Kazmit]

91L 2.0?

[TampaWxLurker]

12z GFS moves it directly over Bermuda, heading ENE at +246 hrs, 1000mb

[LarryWx]

12Z UKMET: ~150 miles E of Bermuda

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 24 HOURS
FORECAST POSITION AT T+ 24 : 20.0N 50.9W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 18.09.2025 24 20.0N 50.9W 1009 35
0000UTC 19.09.2025 36 20.8N 53.2W 1009 31
1200UTC 19.09.2025 48 21.3N 55.3W 1010 29
0000UTC 20.09.2025 60 22.4N 58.1W 1011 30
1200UTC 20.09.2025 72 23.6N 59.5W 1011 27
0000UTC 21.09.2025 84 25.1N 61.1W 1011 29
1200UTC 21.09.2025 96 26.9N 61.2W 1011 33
0000UTC 22.09.2025 108 29.3N 62.0W 1008 43
1200UTC 22.09.2025 120 31.2N 62.2W 1007 47
0000UTC 23.09.2025 132 33.5N 61.9W 1005 41
1200UTC 23.09.2025 144 36.5N 58.5W 1003 42
0000UTC 24.09.2025 156 39.5N 52.7W 994 43
1200UTC 24.09.2025 168 42.3N 44.3W 982 52

[LarryWx]

12Z summary of main ops

-Icon H 250 miles E/SE of Bermuda 9/22-3
-GFS another relatively weak run with a TS over Bermuda but takes 10 days (9/27)!
-CMC H 150 miles E/SE of Bermuda 9/22
-Euro H 200 miles E/SE of Bermuda 9/22
-UKMET: TS ~150 miles E of Bermuda 9/22
-JMA out to only 72 as a TD recurving

[USTropics]

91L 2.0?

In all seriousness, it'll be interesting to see how Gabrielle deals with the environment in the next 3-4 days. I had to rush this analysis before my next class, but here is what I'm seeing as the big picture in WV imagery:



We have a couple upper-level lows (ULLs, red) that are working in tandem to produce southwesterly shear (dashed lines) over the system. Their is no defined low-level circulation currently, so the NHC position is the 'mean' of the wind radii (green, which looks something like this ):


In addition, the GFS has trended with a more westerly position over the past 8 runs in ~3 days time. This is putting the system closer to the shear axis as well as a much drier mid-level air mass:


A stronger system before it reaches this longitude (as in earlier GFS runs and other operational models) allows Gabrielle to fight off this shear axis and dry air (in some situations, even rain-filling the ULL to the west and degrading it to a point that Gabrielle gets into a much more conducive environment).

[LarryWx]

0Z UK actually weakens Gabrielle over the next 3 days before passing to the E of Bermuda as a TD and then it gets much stronger well to the N;

TROPICAL STORM GABRIELLE ANALYSED POSITION : 19.4N 48.7W

ATCF IDENTIFIER : AL072025

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
0000UTC 18.09.2025 0 19.4N 48.7W 1007 38
1200UTC 18.09.2025 12 20.3N 51.1W 1007 34
0000UTC 19.09.2025 24 20.9N 52.9W 1008 30
1200UTC 19.09.2025 36 22.5N 55.1W 1010 30
0000UTC 20.09.2025 48 23.6N 57.4W 1011 29
1200UTC 20.09.2025 60 24.9N 59.5W 1011 28
0000UTC 21.09.2025 72 26.1N 60.7W 1011 27
1200UTC 21.09.2025 84 28.6N 61.6W 1010 29
0000UTC 22.09.2025 96 30.6N 62.2W 1006 31
1200UTC 22.09.2025 108 32.7N 61.6W 1005 34
0000UTC 23.09.2025 120 36.0N 59.1W 1003 38
1200UTC 23.09.2025 132 39.7N 55.2W 995 43
0000UTC 24.09.2025 144 42.0N 47.6W 984 52
1200UTC 24.09.2025 156 44.7N 39.9W 974 57
0000UTC 25.09.2025 168 49.0N 34.1W 971 53