Tropical Wave SW of the Cabo Verde Islands (30/70)

[Hypercane_Kyle]

I know it's early but considering the current synoptic pattern over the CONUS right now it would be incredibly hard for a system to make it even as far west as Erin did. We'll see of course but my bet is on a hard recurve.

[zzzh]

AI models (EC Aifs, Google DM) have the track a lot further south compared to the global models.

[Category5Kaiju]

I've recently wondered about this concept quite a bit, especially while looking at the models for this current AOI as well as the models when Erin was active. I do want to hear others' thoughts about it if possible.

When Erin happened, there were quite a few comments that basically were like, "oh, it's early, you can't say Erin is going OTS, look how the models initially had Irma going OTS," to which such were rebutted with comments like "models have gotten a lot better since 2017." Upon looking back at Erin and some of the recent big fish storms that at some point in their lives raised suspicions that they could impact land (Sam or Lee to name a few), it's hard not to ignore the idea that models did very well, even early-on, with nailing the general track (in other words, if it smelled fishy at first, it ultimately did turn out fishy).

So...I guess the thought I want to raise is: do you think the models we currently have would've better seen Irma (or Florence for that matter too) impacting land early-on? Do you think that these same models would've correctly seen the westward bend if they were theoretically tasked to track a storm like Hugo, Isabel, or Andrew? Or....do you think that no matter what, due to the high volatility of steering patterns, such an early diagnosis wouldn't really be possible and that the models' default idea would always be a spaghetti of OTS tracks?

[LarryWx]

I've recently wondered about this concept quite a bit, especially while looking at the models for this current AOI as well as the models when Erin was active. I do want to hear others' thoughts about it if possible.

When Erin happened, there were quite a few comments that basically were like, "oh, it's early, you can't say Erin is going OTS, look how the models initially had Irma going OTS," to which such were rebutted with comments like "models have gotten a lot better since 2017." Upon looking back at Erin and some of the recent big fish storms that at some point in their lives raised suspicions that they could impact land (Sam or Lee to name a few), it's hard not to ignore the idea that models did very well, even early-on, with nailing the general track (in other words, if it smelled fishy at first, it ultimately did turn out fishy).

So...I guess the thought I want to raise is: do you think the models we currently have would've better seen Irma (or Florence for that matter too) impacting land early-on? Do you think that these same models would've correctly seen the westward bend if they were theoretically tasked to track a storm like Hugo, Isabel, or Andrew? Or....do you think that no matter what, due to the high volatility of steering patterns, such an early diagnosis wouldn't really be possible and that the models' default idea would always be a spaghetti of OTS tracks?

Keep in mind though that Erin ended up tracking 200 miles NW of where the NHC had its westernmost point <4 days prior thanks to model consensus having been that much off. That meant the difference between a minimal TS wind impact along with significant storm surge and having much less than that. This really wasn’t a fish storm with regard to significant impacts on the US.

[OuterBanker]

Both GFS and Euro go fishing. One note though. The 12Z GFS went fishing around 58W. 18z around 70w. Pretty big shift west.

But it is the 18z usually the dramatic outlier.

[LarryWx]

For the first time in a couple of days, the UKMET (0Z) has TCG for this. However, after moving WNW, then WSW for a short time, and then back to WNW, it dissipates at 16.4N, 48.3W:

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 72 HOURS
FORECAST POSITION AT T+ 72 : 15.0N 35.4W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
0000UTC 05.09.2025 72 15.0N 35.4W 1011 28
1200UTC 05.09.2025 84 15.6N 37.0W 1012 26
0000UTC 06.09.2025 96 15.9N 39.8W 1012 28
1200UTC 06.09.2025 108 16.4N 42.7W 1012 32
0000UTC 07.09.2025 120 16.0N 45.7W 1013 29
1200UTC 07.09.2025 132 16.4N 48.3W 1013 29
0000UTC 08.09.2025 144 CEASED TRACKING

[ouragans]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Tue Sep 2 2025

Eastern Tropical Atlantic:
A tropical wave located over the far eastern tropical Atlantic south
of the Cabo Verde islands is producing disorganized showers and
thunderstorms. Environmental conditions appear conducive for
gradual development of this system, and a tropical depression could
form by the middle or latter part of this week. This system is
expected to move westward to west-northwestward at around 15 mph
across the eastern and central tropical Atlantic throughout the
week.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 7 days...medium...60 percent.

[kevin]

00z GFS is slightly west of 18z, but also way faster. Recurves just east of Bermuda. Already forms within 48 hours and becomes a hurricane within 5 days. Not sure I buy the fast development GFS keeps showing.



00z ICON shows slower development than GFS and is very similar to 12z ICON. TS genesis in 3 - 4 days and a hurricane around day 6 - 7. Way more south than GFS.



00z Euro is the other extreme with extremely slow development. Doesn't even get below 1000 mb until 12 days out and develops as it recurves. Goes just east of Bermuda.

[kevin]

So in conclusion, still very uncertain. The 00z GEFS seems to indicate recurve all the way with the only potential threat being for Bermuda, while 00z Euro is about as ominous as an ensemble has been so far this season for the islands (and potentially the US).

GEFS



Euro

[cycloneye]

It looks like this wave will be a invest later today or tonight and here is the link to the invests and TC's. Refresh it to see if 91L appears and anyone can start the 91L invest discussion thread. I will not as I have done it many times and we are looking for the members to have participation.

https://ftp.nhc.noaa.gov/atcf/btk/

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Tue Sep 2 2025

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

Eastern Tropical Atlantic:
A tropical wave located over the far eastern tropical Atlantic south
of the Cabo Verde islands is producing disorganized showers and
thunderstorms. Environmental conditions appear conducive for
gradual development of this system during the next several days, and
a tropical depression is likely to form later this week or this
weekend. This system is expected to move westward to
west-northwestward at around 15 mph across the eastern and central
tropical Atlantic through the weekend.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 7 days...high...70 percent.

$$
Forecaster Brown

[BobHarlem]

I guess getting an invest tag is about 50/50 today with these types of odds, if not, until the shorter term 48 hour percentage goes up more. Satellite isn't looking too great on the area now. Lots of the ensembles cut off right before the likely spot of recurve. From eyeballing all of the models tracks and 500mb steering, this one may get closer to the islands, but probably curves sharper and wouldn't be shocked to see it get a lot closer to Bermuda than Erin got.

[Cachondo23]

Not sure how models have this development when there is a TUTT and some dry air in the MDR.

[ChrisH-UK]

Looks like its starting to nicely curl up

GOES-19 GeoProxy 2hr Loop

[cycloneye]

Good post from MIchael Lowry.

 https://x.com/MichaelRLowry/status/1962863383767638380

[DorkyMcDorkface]

Not sure how models have this development when there is a TUTT and some dry air in the MDR.

Its low latitude is helping it get support from the monsoon trough, and it will receive a boost from a passing CCKW (despite the general background state being hostile at the present time). I think the stronger it gets in the shorter term the higher the likelihood of it putting up a fight against the TUTT, with some models such as the GFS showing it releasing enough latent heat to splinter it and break off an ULL from it. Granted the GFS also has it gaining more latitude than the other models during that time, making it a bit of an outlier at the moment.

[Woofde]

I've recently wondered about this concept quite a bit, especially while looking at the models for this current AOI as well as the models when Erin was active. I do want to hear others' thoughts about it if possible.

When Erin happened, there were quite a few comments that basically were like, "oh, it's early, you can't say Erin is going OTS, look how the models initially had Irma going OTS," to which such were rebutted with comments like "models have gotten a lot better since 2017." Upon looking back at Erin and some of the recent big fish storms that at some point in their lives raised suspicions that they could impact land (Sam or Lee to name a few), it's hard not to ignore the idea that models did very well, even early-on, with nailing the general track (in other words, if it smelled fishy at first, it ultimately did turn out fishy).

So...I guess the thought I want to raise is: do you think the models we currently have would've better seen Irma (or Florence for that matter too) impacting land early-on? Do you think that these same models would've correctly seen the westward bend if they were theoretically tasked to track a storm like Hugo, Isabel, or Andrew? Or....do you think that no matter what, due to the high volatility of steering patterns, such an early diagnosis wouldn't really be possible and that the models' default idea would always be a spaghetti of OTS tracks?

While models are better than 2017, they definitely still have their misses. Just in the last two years I can think of 3 rough misses at lead times far less than those of most recurving fish storms:

1. Otis rapidly intensying and striking Mexico.

2. Oscar becoming a hurricane and striking Cuba.

(Now yes these were intensity errors and not track errors which are harder to predict, but they also happened much closer to the US. We should have better data collection here than the open ocean)

3. Beryl coming to Houston, the global models and many established mets were insistent upon it burying into Central America. The models still often miss on Track.

With weather the chaotic unpredictability compounds too fast; the old "A butterfly flaps it's wings" effect. A weather model capable of confidently predicting fish storm or land at hour [240] may never exist, even tiny errors compound.

The synoptics for the tropical wave we are currently looking at have already drastically changed over the last week. Models changed from ejecting it North quickly with minimal development, to now a potential long lived MDR storm.

[LarryWx]

Good post from MIchael Lowry.

 https://x.com/MichaelRLowry/status/1962863383767638380

My concern is that Google Deepmind ensembles, which I know little about, did best with Erin per Lowry. As one can see from Lowry’s image, its 0Z 9/2 run has 6 of its members from the E MDR AEW in a very dangerous location at/near the Lesser Antilles. What I don’t know is how many total members it has. Lowry’s diagram makes it look like most members go toward the Caribbean, but there are only 6 that actually get there by hour 210. Many are slower (still well E) and 4 of them are turning WNW to NW (at the top of his yellow circle) and we can’t see where they go after hour 210. Also, there are two that are just starting to sharply recurve well E of the Caribbean but still within the MDR. But regardless, this ensemble’s avg trajectory does look more dangerous than the EPS and is totally different from the GEFS.

[lsuhurricane]

The Google Deepmind ensembles bear a close resemblance to the 6z EURO-AIFS ensembles. Notice the bifurcation near the Islands. Interesting times ahead.

[TomballEd]

I'm not unaware of the ensembles that bring it close enough to the E Car to be a threat but I suspect a recurve E of Bermuda with the storm being N of 30 degrees before it reaches peak strength.

70% sounds like this should be an invest soon.