ATL: Ex INVEST 99L - Discussion

[weeniepatrol]

ASCAT pass that just hit 99L:
https://i.ibb.co/DgRZHxZp/ascat-wind-99-L-202508192251.webp

Thanks! Looks very close, though perhaps not quite there yet. On satellite, it does look like southerlies are present on the eastern side.

[HurricaneAndre2008]

ASCAT pass that just hit 99L:
https://i.ibb.co/DgRZHxZp/ascat-wind-99-L-202508192251.webp

Looks good to me.

[AJC3]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Wed Aug 20 2025

Eastern Tropical Atlantic (AL99):
Recent satellite-derived wind data indicate that a concentrated
area of showers and thunderstorms located just southwest of the Cabo
Verde Islands lacks a closed surface circulation. Environmental
conditions appear marginally favorable for additional development
over the next day or so while the system moves westward at around 15
mph. By the end of the week, environmental conditions are expected
to become unfavorable for further development.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 7 days...low...30 percent.

[abajan]

6Z Best Track:

AL, 99, 2025082006, , BEST, 0, 134N, 269W, 30, 1011, DB...

[TomballEd]

No ensemble support for this near term and the remnants making a comeback in the Caribbean is far from a guaranteed thing.

It looks like it should be the mandarin but models suggest 30/30 is generous.

[BobHarlem]

99L this morning. That microwave makes me think 30% is too low.

[cycloneye]

Eastern Tropical Atlantic (AL99):
A tropical wave located to the southwest of the Cabo Verde Islands
continues to produce a concentrated area of showers and
thunderstorms. Environmental conditions appear marginally favorable
for additional development over the next day or so while the system
moves westward at around 15 mph and a short-lived tropical
depression could form. By the end of the week, environmental
conditions are expected to become unfavorable for further
development.
* Formation chance through 48 hours...medium..40 percent.
* Formation chance through 7 days...medium...40 percent.

[TomballEd]

It may be short lived but it looks like a TC on the Navy Monterey image posted and visible satellite. The center is covered by storms so I can't tell for certain if there is a closed low, but I suspect there is. Has a day and a half if GFS is guide before getting murdered by shear.

A couple of lows which may or may not be developing from what is left of 99L in the SW Caribbean in 12 days on 6Z GEFS but I'm leaning against 99L being anything after its quick promotion to depression or storm.

[Kingarabian]

Likely been a TC for the past 24 hours. Has maintained convection. Has a closed center.

[cycloneye]

AL, 99, 2025082012, , BEST, 0, 115N, 291W, 30, 1011, DB

[zhukm29]

ASCAT shows closed, with max detected winds of 34.5kt. I think this may be enough for designation. That microwave a few posts earlier is quite telling.

[Powellrm]

Whoa I had not been keeping my eyes on this one, it would appear to be getting its act together. Impressively.

[cycloneye]

[Kingarabian]

Not sure whats the hold up to be honest. Setting up dual banding features on visible.

[Teban54]

[zhukm29]

I think 99L looks better than Erin did when it was first designated off the African coast. Only difference is that models don’t think it will last long and will run into unfavorable conditions tomorrow so any designation will need to be done today. We’ll see what happens, but I do hope this ends up being recorded as a TC even if it’ll end up as a short-lived system.

[zzzh]

 https://x.com/WeathermanAAA_/status/1958212188981932108

[South Texas Storms]

Still at 40% by NHC at 1pm CDT.

Eastern Tropical Atlantic (AL99):
Satellite-derived surface wind data from earlier today revealed that
a concentrated area of showers and thunderstorms located several
hundred miles southwest of the Cabo Verde Islands lacks a closed
surface circulation. Environmental conditions appear marginally
favorable for additional development over the next day or so while
the system moves west-southwestward at around 15 mph and a
short-lived tropical depression could form. By the end of the
week, environmental conditions are expected to become unfavorable
for further development.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...medium...40 percent.

[AutoPenalti]

I don't think there's a point in wasting a designation for a system that:

1) models aren't showing
2) feature that will likely dissipate after a couple of days

post-season they'll probably upgrade it

(watch this system bite me in the ass right after i post this)

[ConvergenceZone]

It looks like September will be the month where we will see USA landfalling threats. I guess this is normal though since storms typically fall apart or recurve when they form in August or earlier. September will more than likely be a much different story. I just don't see us getting through the whole month of September without at least one USA mainland landfall. I would be absolutely shocked if that happened.