ATL: Ex INVEST 91L - Discussion (0/0)

[Woofde]

Models have drastically dropped off with 91L this morning. Don’t think this will form at all now which is going to seriously hurt the season and raises a lot of questions of what is causing the Atlantic to remain this anemic even into peak season.

There's still a decent amount of model support and it looks okay. Vorticity has slowly been improving the past 12 hours. I wouldn't write it off yet just from a couple model cycles, the trend is promising though.

[TomballEd]

I think it looked better yesterday. I expected DMAX to have this on the edge of being a TC today. There are W winds to the S of the elongated wave but I think that is mainly the MT. Cloud tops on the southern portion of the wave are being blown off to the N, indicating S shear. The N part of the wave is not convectively active.


Slow development means it gets farther W before feeling any weaknesses in the ridge to its N

[cycloneye]

Is a sharp wave axis.

 https://x.com/AndyHazelton/status/1963980757417799798

[WeatherBoy2000]

Is a sharp wave axis.

 https://x.com/AndyHazelton/status/1963980757417799798

Given the continued lack of organization and the model downtrend over the last 24 hours, I won't be surprised if the nhc begins lowering chances of development soon.

[MGC]

91L is looking rather shabby today. I was thinking earlier in the week that a circulation would close off this weekend, I am now doubting that will occur. Looking at the sat loop I see no evidence of a surface circulation. MCL might bore down in a few days though.....MGC

[AutoPenalti]

NHC will most likely reduce chances on the next TWO

[Nimbus]

Lots of Stratocumulus clouds in the area near 14N where the apex of the wave was trying to close off.
Dry stable air will delay development and keep the track further south.

[cycloneye]

NHC will most likely reduce chances on the next TWO

Agree 100% with that.

[MarioProtVI]

No model has development now after 12z GFS and ICON both dropped out. Incredible turnaround from just 2 days ago when it seemed surefire that this could’ve been our next hurricane. Says a lot about the state of 2025 in the Atlantic besides Erin.

[wxman57]

Not looking good for development of this one. It's main proponent of development, the GFS, is no longer developing it. Maybe chances closer to 10%/40%.

[Category5Kaiju]

I will admit, I’m actually quite stunned to see how drastically the models and prospects for this to develop into a hurricane have basically petered out. Great for the islands, but also….a head-scratcher to say the least, at least from a meteorological perspective. Were there negative factors that these major models didn’t see merely days ago that caused such a turnaround?

[TampaWxLurker]

I will admit, I’m actually quite stunned to see how drastically the models and prospects for this to develop into a hurricane have basically petered out. Great for the islands, but also….a head-scratcher to say the least, at least from a meteorological perspective. Were there negative factors that these major models didn’t see merely days ago that caused such a turnaround?

From what I've read, mid-level dry air and shear.

[wxman57]

I will admit, I’m actually quite stunned to see how drastically the models and prospects for this to develop into a hurricane have basically petered out. Great for the islands, but also….a head-scratcher to say the least, at least from a meteorological perspective. Were there negative factors that these major models didn’t see merely days ago that caused such a turnaround?

From what I've read, mid-level dry air and shear.

Yes, that is true. Not a very favorable environment. I'm going 10%/40%, and that could be generous for the next 48 hrs. NHC went with the GFS solution of taking Lorena into the Baja Peninsula as a hurricane. That didn't work out well. Other models had it dissipating offshore. GFS hasn't been doing well in any basin over the past year. It WAY overdevelops disturbances, like the Canadian used to do. GFS can no longer be trusted as a tropical model.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Fri Sep 5 2025

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

Tropical Atlantic (AL91):
Shower and thunderstorm activity is currently limited and
disorganized in association with a tropical wave over the central
tropical Atlantic. Although upper-level winds are generally
favorable for development, environmental dry air is likely to limit
development over the next couple of days. However, a tropical
depression could still form early next week as the system moves
westward at around 10 mph across the central tropical Atlantic. This
system is likely to be near the Lesser Antilles by the middle to
latter part of next week, and interests there should monitor its
progress.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...high...70 percent.

$$
Forecaster Hagen

[TomballEd]

I will admit, I’m actually quite stunned to see how drastically the models and prospects for this to develop into a hurricane have basically petered out. Great for the islands, but also….a head-scratcher to say the least, at least from a meteorological perspective. Were there negative factors that these major models didn’t see merely days ago that caused such a turnaround?

From what I've read, mid-level dry air and shear.

Yes, that is true. Not a very favorable environment. I'm going 10%/40%, and that could be generous for the next 48 hrs. NHC went with the GFS solution of taking Lorena into the Baja Peninsula as a hurricane. That didn't work out well. Other models had it dissipating offshore. GFS hasn't been doing well in any basin over the past year. It WAY overdevelops disturbances, like the Canadian used to do. GFS can no longer be trusted as a tropical model.

IMBY concern, does the low level wave survive passage into the Caribbean to become a Central America or East Pac threat?

[Hurricane Jed]

I will admit, I’m actually quite stunned to see how drastically the models and prospects for this to develop into a hurricane have basically petered out. Great for the islands, but also….a head-scratcher to say the least, at least from a meteorological perspective. Were there negative factors that these major models didn’t see merely days ago that caused such a turnaround?

Why?

From what I've read, mid-level dry air and shear.

Yes, that is true. Not a very favorable environment. I'm going 10%/40%, and that could be generous for the next 48 hrs. NHC went with the GFS solution of taking Lorena into the Baja Peninsula as a hurricane. That didn't work out well. Other models had it dissipating offshore. GFS hasn't been doing well in any basin over the past year. It WAY overdevelops disturbances, like the Canadian used to do. GFS can no longer be trusted as a tropical model.

Gotta follow up. Why shouldn’t we trust the GFS?

[al78]

Gotta follow up. Why shouldn’t we trust the GFS?

It does seem in general to be very trigger happy. If climatology resembled the GFS model, global tropical cyclone counts would be at least double what they are now.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Fri Sep 5 2025

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

Tropical Atlantic (AL91):
Shower and thunderstorm activity remains limited in association with
a tropical wave over the central tropical Atlantic. A drier air mass
is limiting the potential for development over the next couple of
days, and environmental conditions will remain only marginally
favorable thereafter. A tropical depression could form during the
early to middle part of next week as the system moves westward at
around 10 mph across the central tropical Atlantic. This system is
likely to be near the Lesser Antilles by the middle to latter part
of next week, and interests there should monitor its progress.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 7 days...medium...60 percent.

$$
Forecaster Kelly

[MarioProtVI]

Think it’s time to bring out Bones me thinks

[cycloneye]

AL, 91, 2025090600, , BEST, 0, 120N, 366W, 25, 1011, DB