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

[WaveBreaking]

18z has the wave dramatically ramp up from a 1000 mb depression to a strengthening 980 mb hurricane into the Yucatan. The only major difference between steering that I can find between the 12z and 18z is that the ridge over the N gulf is slightly stronger in the 18z run.

[WaveBreaking]

This is interesting, AIFS 12z suddenly got onboard the GoM system from the gyre over Yucatan (from our AOI) trend.

12z EPS also had an uptick in members showing that solution

https://i.imgur.com/T1MKfx5.png

https://i.imgur.com/4WgEUDs.png

Can someone please explain what the different colored lines mean?

Each line is an area of low pressure that one of the members in the European Ensemble model group tries to develop. The color corresponds to the strength of a low pressure area developed by a member (the legend in the top right shows the pressure values associated with each color).

[WaveBreaking]

18z run decides to split the wave into two after getting buried in CA.

[Teban54]

18z run decides the split the wave into two after getting buried in CA.

https://i.imgur.com/SU9UdB5.gif

This scenario had been shown on some earlier runs, and did happen in real life with Julia and Karl 2022.

[Stratton23]

While the GFS/ GEFS on this run goes into mexico, the upper air pattern is very tricky next week, the ridging on the GEFS isnt even all that strong and still has a weakness over the western- central gulf coast states, its just a question if something develops and feels that weakness

[cheezyWXguy]

The gfs’s evolution of this system after Mexico landfall seems strange, but does have some support from the gefs/eps. If steering currents do break down like that with a weakness to the north, it should have a fair amount of time to capitalize on warm waters and at least a decent environment

[Teban54]

Didn't know there are more than one Euro AI models. Apparently, the other two were much less trigger-happy worth genesis than AIFS was, but now all three show a BoC system heading north.

 https://x.com/MassachusettsWx/status/1830742292866674858

[cajungal]

Didn't know there are more than one Euro AI models. Apparently, the other two were much less trigger-happy worth genesis than AIFS was, but now all three show a BoC system heading north.

 https://x.com/MassachusettsWx/status/1830742292866674858

I haven’t been watching as much today because been enjoying my Labor Day with nice weather and a pool day but a little surprised to see a model showing this as I am in Louisiana.

[TomballEd]

The GFS solution is weird. Multiple TCs from the remnants of the AOI probably doesn't happy. Solution through one week is stronger than prior runs, and possible. A bit more N it could feel the trough bringing the first real Autumn cold front (dew points at or below 60F!) and come N.

10% of the 18Z ensembles do something possibly associated with the now 0% AOI, pushing lows S ahead of the front, which could interact, somehow, with this AOI. Feels like drawing to an inside straight, but I suppose the odds of something ICON-sh or 18Z GFS-ish happening are non-zero.

[Weathertracker96]

Does anyone what causes the GFS to send a system to FL in the latest run?
Is it related to this wave or is part of another wave?
It’s been showing up on some runs.

[cycloneye]

Caribbean Sea:
A westward-moving tropical wave is producing disorganized showers
and thunderstorms accompanied by locally heavy rainfall and strong
gusty winds over portions of the eastern Caribbean Sea and the
adjacent land areas. Environmental conditions are forecast to
become more conducive for development when the system reaches the
western Caribbean Sea and southwestern Gulf of Mexico late this week
and over the weekend, and a tropical depression could form during
that time.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...medium...40 percent.

[Stratton23]

NHC is being too conservative again, i really think they should have upped this to 50% at the 8 pm update

[ThunderForce]

Oddly a lot of the 18z GEFS ensembles seem a bit faster than the operational model with this tropical wave.

[Spacecoast]

Didn't know there are more than one Euro AI models. Apparently, the other two were much less trigger-happy worth genesis than AIFS was, but now all three show a BoC system heading north.

 https://x.com/MassachusettsWx/status/1830742292866674858

Actually more than three....
Here's a link to ECMWF Experimentals...
https://charts.ecmwf.int/?facets=%7B%22Product%20type%22%3A%5B%22Experimental%3A%20Machine%20learning%20models%22%5D%7D

There's also GFS version of Graphcast on Pivotal

[Hammy]

Oddly a lot of the 18z GEFS ensembles seem a bit faster than the operational model with this tropical wave.

Euro still doesn't develop it and the GFS has been off and on, so more likely there isn't enough confidence right now

[Stratton23]

The euro OP will eventually cave in to the ensemble, happens almost every time with that model, at least 20 of the 50 members show development, thats pretty good, the GFS is starting to show a more consistent run to run variance in terms of development, not strength , id frankly be shocked if the NHC didnt up chances at 2 am

[Craters]

This is interesting, AIFS 12z suddenly got onboard the GoM system from the gyre over Yucatan (from our AOI) trend.

12z EPS also had an uptick in members showing that solution

https://i.imgur.com/T1MKfx5.png

https://i.imgur.com/4WgEUDs.png

Can someone please explain what the different colored lines mean?

Each line is an area of low pressure that one of the members in the European Ensemble model group tries to develop. The color corresponds to the strength of a low pressure area developed by a member (the legend in the top right shows the pressure values associated with each color).

And just to add a bit to WaveBreaking's nice, concise explanation, 1 hPa (hectoPascal) = 1 millibar.

You'll see these "ensemble" plots here fairly often. One thing you'll probably notice after seeing a bunch of them is, all other things being equal under "normal" (!) conditions, the redder and pinker tracks (indicating stronger storms) will have more northerly components to their motion, since stronger storms want to head north. The bluer and greener (weaker) ones are steered more commonly by the prevailing, lower-altitude winds winds at these latitudes.

[TomballEd]

The euro OP will eventually cave in to the ensemble, happens almost every time with that model, at least 20 of the 50 members show development, thats pretty good, the GFS is starting to show a more consistent run to run variance in terms of development, not strength , id frankly be shocked if the NHC didnt up chances at 2 am

A lot of those 10-20 knot or 20-30 knot TDs and minimal TCs are not from the AOI.

The 40% is too low, Dr. Pasch at NHC is making a mistake? Besides having been a professor at both Miami and Florida State, he was a visiting science at ECMWF in England.

[Frank P]

The euro OP will eventually cave in to the ensemble, happens almost every time with that model, at least 20 of the 50 members show development, thats pretty good, the GFS is starting to show a more consistent run to run variance in terms of development, not strength , id frankly be shocked if the NHC didnt up chances at 2 am

I wonder if they take into account the AI models, anyone ever remember when they might have referenced it in a Storm discussion, I don’t recall. Per the IR images convection is really cooling down tonight. I doubt they will increase the percentages based on Sat imagery, unless some big changes occur in the OOz runs this later this evening.

[Stratton23]

TomballEd yes 40% is too low in my opinion, their has been enough uptick in ensemble support and global runs to justify that, the NHC is great at what they do, but they definitely do have a history of being too conservative with development chances