Tropical Wave in Bay of Campeche (Is Invest 91L)

[SFLcane]

Uptrend here no doubt.. Let’s see it hold.

[Ubuntwo]

18z EPS looks like an uptick with ~40% of members with a TS by day 7. The GEFS similarly ticked up to ~35% at 18z, climbing later in the run. Windshield wipering or the start of a trend?

Per my eyeballs, I count at least 13 of the 31 GEFS members on TT with a TC. And based on more eyeballing, this looks like the most active from the current lemon since the 18Z two days ago. I wouldn’t read too much into this though as it could just be a one off run. Let’s see what 0Z shows.

I know Teban has been counting more closely the members. Is this the most active for just the lemon since the 6Z of 8/26?

Glad there's still interest! To be honest, I kind of skipped 12z because it was hard to tell the members that developed this wave past Lesser Antilles, but let me try again.

GEFS member low pressure counts (±2, out of 31):

• 18z 8/28: 13 (42%) as of Eastern Caribbean
• 12z 8/28: 7 (23%) as of Eastern Caribbean (a few members start in WCar, but unsure if they're from this wave or a CAG)
• 6z 8/28: 9 (29%)
• 0z 8/28: 9 (29%)
• 18z 8/27: 4 (13%)
• 12z 8/27: 9 (29%)
• 6z 8/27: 14 (45%)
• 0z 8/27: 9 (29%)
• 18z 8/26: 19 (61%)
• 12z 8/26: 17 (55%)
• 6z 8/26: 19 (61%)
• 0z 8/26: 16 (52%)
• 18z 8/25: 10 (32%)
• 12z 8/25: 14 (45%)

EPS member low pressure counts (±3, out of 51):

• 18z 8/28 (out to 144 hrs only): 33 (65%, some may not be TCs)
• 12z 8/28: 18 (35%) as of Eastern Caribbean (a few members dissipate there, a few develop in WCar)
• 6z 8/28 (out to 144 hrs only): 21 (41%, some may not be TCs)
• 0z 8/28: 11 (22%)
• 18z 8/27 (out to 144 hrs only): 15 (29%)
• 12z 8/27: 14 (27%)
• 6z 8/27 (out to 144 hrs only): 20 (39%)
• 0z 8/27: 25 (49%)
• 18z 8/26 (out to 144 hrs only): 27 (53%)
• 12z 8/26: 34 (67%)
• 0z 8/26: 22 (43%)
• 12z 8/25: 11 (22%)

Today's 18z EPS is close to the most active run ever (that's 12z 8/26), though that's helped by a few members that seem to only have the low form in Eastern Caribbean. Note that not all of these systems are TCs, never mind TSes. On the other hand, some members may also only develop the wave once it gets to Western Caribbean or the Gulf.

18z GEFS is the most active over the past 6 runs, but still less so than the most active day ever (8/26). However, it's a quality-over-quantity situation, as the members that do form are pretty strong as they hit or brush the Caribbean islands.

I looked member-by-member to get the 40% count for the latest EPS. The additional ~25% look like closed or nearly closed lows on the verge of developing, but not truly classifiable by day 7. In absolute numbers that puts it close to 12z 8/26, though that run had a much higher proportion of intense members by day 7. The story for today is continued moderate support with increased chances of delayed development. And chances that we see nothing are still around a coin flip.

[Spacecoast]

18z EC-AIFS

[LarryWx]

18z EC-AIFS
https://i.ibb.co/sKb5stL/ec-aifs-mslp-wind-watl-fh96-312.gif

Wow, this is bizarre! To review, 23 straight EC-AIFS runs from 6Z 8/19 through 18Z 8/24 had TCG ~9/2 near the Leewards. Then the next 15 had nothing (not even a weak sfc low) anywhere around there. Now all of the sudden, the 18Z 8/28 EC-AIFS has a weak sfc low (though not a TC) that forms on 9/2 near the central Lesser Antilles (so a little S of those 23 runs).

[Teban54]

18z EC-AIFS
https://i.ibb.co/sKb5stL/ec-aifs-mslp-wind-watl-fh96-312.gif

Wow, this is bizarre! To review, 23 straight EC-AIFS runs from 6Z 8/19 through 18Z 8/24 had TCG ~9/2 near the Leewards. Then the next 15 had nothing (not even a weak sfc low) anywhere around there. Now all of the sudden, the 18Z 8/28 EC-AIFS has a weak sfc low (though not a TC) that forms on 9/2 near the central Lesser Antilles (so a little S of those 23 runs).

This is the moment when I have to wonder how much ECAI learned on the climo during training. I assume the training data being fed into the model is a large amount of historical weather data, which includes past hurricane tracks. It can pick up signals that "on September 2, there's an elevated chance of a TC near Puerto Rico and an elevated chance of a Caribbean cruiser". How much role that plays relative to current conditions is unknown, perhaps even to the machine learning engineers.

[Ubuntwo]

0z ICON is developing a TS again, right around the 5 day mark. Tracks through the eastern Caribbean while steadily intensifying. Edit: Appears to end the run as a hurricane in the Central Caribbean.

[Stratton23]

ICON finishes its run with a hurricane headed due west, big strong ridge to its north, looks like a gulf storm if the model went out any further

[Category5Kaiju]

Looks like we are starting to see some subtle signs that whatever forms out of this AOI isn't going to easily recurve on out to sea, unlike model ideas several days ago.

[MarioProtVI]

If current trends continue, this could be another Caribbean Crusier that racks up a good amount of ACE, perhaps close to around 20-25 ACE, IF it continues west. Let’s see though. Maybe the switch flip is kicking in for real now and just got delayed somewhat by weird atmospheric processes.

[Teban54]

0z GFS out to 126 hrs has the most concentrated vorticity for this system out of all its runs -- by far -- entering the Caribbean as a low rider, well south of its ensembles. Seems to be on its way to development even with no notable low pressure yet (edit: 1011 mb in the next frame).

Edit 2: Clear-cut TC in the Caribbean by 162 hrs.

[AtlanticWind]

Gfs showing a little something now, model support definitely increasing this evening.

[Ubuntwo]

0z GFS out to 126 hrs has the most concentrated vorticity for this system out of all its runs -- by far -- entering the Caribbean as a low rider, well south of its ensembles. Seems to be on its way to development even with no notable low pressure yet (edit: 1011 mb in the next frame).

https://i.postimg.cc/4y9dh8HY/image.png

Well, it did have the run with the recurving hurricane That one came into the Carib as a strong storm. Unlike that run, though, ridging overhead looks stout here. Edit: Scratch that! A perfectly-timed trough pulls it north into Hispaniola

[lsuhurricane]

Canadian has a bonified hurricane headed westward. This one finally has legs…..

[Teban54]

We're back baby, we're so back

(On a more serious note, the last time there was finally model agreement on all globals with the 18z 8/26 GFS run, they immediately started dropping development just 6 hours later. But...)

Edit: More descriptions of each model run in the global models thread.

[Category5Kaiju]

CMC has this taking a Cleo-like track.

[SFLcane]

[SFLcane]

[SFLcane]

[ElectricStorm]

1. Central Tropical Atlantic:
A broad area of disorganized showers over the central Tropical
Atlantic are associated with a tropical wave. Some slow development
of this system is possible this weekend into the middle of next week
while it moves westward to west-northwestward at 10 to 15 mph.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...20 percent.

[Ubuntwo]

0z Euro develops a closed low in just 3 days, and has an intensifying TS in the eastern Caribbean soon after. Similar to the ICON so far.

Edit: Major hurricane in the Caribbean this run. Near Cuba. If the system can avoid land interaction (big if) the ceiling appears quite high...