Tropical Wave off the African Coast (Is Invest 92L)

[gatorcane]

I didn’t see a thread for this. One to watch given time of year and where it may be heading. I believe the Euro develops this and is the one it is showing intensifying east of the northern Lesser Antilles. The GFS brings this to the area just NE of Lesser Antilles in the long-range (animation below)

4. A new tropical wave is expected to emerge off the coast of Africa
in a couple of days. Some gradual development of this system will
be possible through the end of the week while it moves slowly
westward over the far eastern tropical Atlantic Ocean.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...20 percent.

[SFLcane]

12z Ukmet is also developing this wave.

[cycloneye]

A new tropical wave is expected to emerge off the coast of Africa
in a couple of days. Gradual development of this system will be
possible through the end of the week while it moves slowly westward
over the far eastern tropical Atlantic Ocean.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...30 percent.

[toad strangler]

hmmmm

[SFLcane]

[gatorcane]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

[WeatherEmperor]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

[img]https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-f]

Why is Euro showing the wave so weak if it underneath a big favorable high pressure?? Is there dry air around??


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[SFLcane]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-fh96-240.gif

Big trough dipping there at the end Into the CONUS.

[ronjon]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-fh96-240.gif

Big trough dipping there at the end Into the CONUS.

Yes but it isn't progressive and actually may be retrograding west due to strengthening Atlantic Ridge. GFS now depicting something similar after its big fall like trough yesterday.

[SFLcane]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

[url]https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-f]

Why is Euro showing the wave so weak if it underneath a big favorable high pressure?? Is there dry air around??


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RH doesn’t look like a problem.

[LarryWx]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-fh96-240.gif

Big trough dipping there at the end Into the CONUS.

Yes but it isn't progressive and actually may be retrograding west due to strengthening Atlantic Ridge. GFS now depicting something similar after its big fall like trough yesterday.

Out of everything in the tropics now, I think that this wave still over Africa has the highest chance to potentially eventually threaten the E coast of the CONUS with a TC. IF that would even threaten, it wouldn't be for at least 2 weeks or so..say, 9/13-16ish. Also around then, assuming we get the bottom of that cool Canadian high around 9/9-12 (still favored by the 12Z EPS), and IF that aforementioned African wave doesn't actually threaten, we MAY have to worry about something homegrown possibly vaguely similar to Diana of 1984 due to a possibly similar setup to 1984.

But back to this African wave, here's the 12Z EPS hour 360 H5/sfc, which shows a restrengthening WAR (as per ronjon). Also, note the upward kink in the 1016 mb isobar off of Florida, indicative of locally lower pressure:



And here are the individual members showing a TC: all of these are from this same wave:



in summary as of now, I'm thinking most likely a quiet Sep 1-12 tropical threat-wise for the E coast of the CONUS (hopefully including a nice gift from Canada for some), followed by a "watch the tropics" period near midmonth.

[Hurricaneman]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

[url]https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-f]

Why is Euro showing the wave so weak if it underneath a big favorable high pressure?? Is there dry air around??


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RH doesn’t look like a problem.

https://cdn1.bbcode0.com/uploads/2020/8/30/1a5bd223f065f398da6d1125135990a4-full.png

If the Euro and or GFS show a decent MLC under a ridge, that’s cause for concern because the models have been trash when it comes to tropical cyclogenesis

[toad strangler]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

[url]https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-f]

Why is Euro showing the wave so weak if it underneath a big favorable high pressure?? Is there dry air around??


Sent from my iPhone using Tapatalk

Maybe you haven't looked at any models this year I don't know but the globals (sans CMC) have been hideous on genesis with the GFS and Euro leading the hideous pack.

[USTropics]

12Z ECMWF 500mb height progression from hours 96 through 240. The wave can be seen south of the Cabo Verde islands heading west ending up just north of the northern lesser antilles

[url]https://i.postimg.cc/ZKgWc8d5/ecmwf-z500a-Norm-atl-f]

Why is Euro showing the wave so weak if it underneath a big favorable high pressure?? Is there dry air around??


Sent from my iPhone using Tapatalk

Maybe you haven't looked at any models this year I don't know but the globals (sans CMC) have been hideous on genesis with the GFS and Euro leading the hideous pack.

Genesis, and even the developmental process of established systems, has been extremely difficult for the global models to forecast outside of the 72 hour window this year. Hanna, Gonzalo, Marco, and Laura are just examples in the NATL, the same can be said in the other basins. To some surprise, the CMC ensembles (GEPS) has led the way on detecting genesis in advance of the other models/ensembles. This will be another test, as the CMC ensembles have consistently advertised the WGOM the past 5 runs now:



The GFS-para ensembles the past few runs have shown some interest as well:


(this is not the wave exiting Africa, this genesis appears to be from the fractured wave in the central Atlantic)

[cycloneye]

8 PM TWO:

A new tropical wave is expected to emerge off the coast of Africa
in a couple of days. Gradual development of this system will be
possible through the end of the week while it moves slowly westward
over the far eastern tropical Atlantic Ocean.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...30 percent.

[gatorcane]

2pm TWO:

3. A tropical wave is expected to emerge off the coast of Africa in a
day or two. Gradual development of this system will be possible
through the end of the week while it moves slowly westward over the
far eastern tropical Atlantic Ocean.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...30 percent

[SFLcane]

Euro Dangerous position with lots of ridging.

[gatorcane]

Saved 12Z Euro animation from 96 through 240 hours. Ends up just NE of the Lesser Antilles:

[toad strangler]

Euro Dangerous position with lots of ridging.

https://cdn1.bbcode0.com/uploads/2020/8/31/3ffb2ba93c1a45eaa471d1373c3b758c-full.png

Went backwards over yesterday ..... models having a tough time sorting out these waves

[SFLcane]

Saved 12Z Euro animation from 96 through 240 hours. Ends up just NE of the Lesser Antilles:

https://i.postimg.cc/yNnSRnsj/ecmwf-uv850-vort-atl-fh96-240.gif

Dips SW near the islands. Worth keeping an eye on upper level conditions don’t like the best.